On April 8, the moon will pass directly between Earth and the sun, creating a total solar eclipse across much of the United States, Mexico, and Canada.
Although total solar eclipses occur somewhere in the world every 18 months or so, this one is unusual because tens of millions of people in North America will likely witness it, from Mazatlán in Mexico to Newfoundland in Canada.
“It’s a huge communal experience,” says Meg Thacher, a senior lab instructor in the astronomy department at Smith College in Massachusetts. “A total solar eclipse is the Super Bowl of astronomy.” Here’s how to safely watch—and photograph—the natural phenomenon.
Fail to prepare, prepare to fail
It pays to have a plan of action for the day.
Before you decide on a spot to watch the eclipse, whether it’s in your own backyard, in a national park, or at a viewing party, it’s worth checking the weather forecast to see how likely clouds are to spoil the show. Currently the majority of the eclipse’s path of totality—areas where onlookers will see a full eclipse, as opposed to a partial one—is forecast to have some degree of cloud cover.
However, even if visibility turns out to be poor, you still have options. NASA and the National Science Foundation are broadcasting livestreams, and many eclipse viewing parties will broadcast unobstructed views as part of their festivities. The American Astronomical Society has a state-by-state list to help you find your nearest event.
Safety first
You need proper eye protection to look at the eclipse, because the sun’s light can cause long-term damage to your vision. Be sure to purchase either specially made eclipse glasses or handheld solar viewers. Glasses might be the best option if you plan to take photos, as they’ll keep your hands free. Eclipse glasses are thousands of times darker than regular sunglasses and contain a polymer designed to filter out harmful light.
You should also make sure any cameras, binoculars, or telescopes through which you plan to look at the sun have been fitted with a solar filter. You don’t need to double up and wear eclipse glasses if you already have a solar filter, though.
Once the moon fully obscures the sun, it’s safe to remove your eye protection for the duration of the totality, which is projected to last around four minutes during this eclipse.
A proper camera is your best bet …
Photographing an eclipse is pretty simple, says Randall Benton, a professional photographer who has been capturing them since 1979. Although cameras have changed vastly since then, the fundamentals remain the same. (If you plan to use your phone to take photos, skip to the next section.)
He recommends fixing a DSLR or mirrorless camera (equipped with a solar filter to protect both your eyes and the camera itself) to a tripod. A short exposure, which is designed to capture movement, is more likely to capture the details of the sun’s corona—the plasma surrounding it. A longer exposure, which keeps certain elements of pictures in focus while blurring others, is likely to stretch the corona further out. The exposure you choose will depend on the kind of shot you’d like to capture.
Before the eclipse begins, take the time to focus the camera exactly where you want the sun and moon to appear in your shot, and turn off any autofocus function. While some mounts come with an automated tracking feature that will follow the eclipse’s progression, others will require you to move your camera yourself, so make sure you’re familiar with the mount you’ve got to prevent the eclipse from drifting out of your frame.
Then, “when there’s just a sliver of sun left and it’s a few seconds away from disappearing, take the filter off the camera lens,” Benton says. “At the very last moment, there’s a phenomenon called the diamond ring effect, when the last speck of visible sunlight resembles a ring—that’s a great dramatic photo. Once the sunlight reappears, it’s time to put the filter back on.”
… but smartphones work too
Despite the rapid advances in smartphone cameras over the past decade or so, they can’t really rival DSLR or mirrorless cameras when it comes to capturing an eclipse.
Their short lenses means the sun will appear very small, which doesn’t tend to produce great photographs. That said, you can still capture the best photo possible by cutting out the plastic lens from a pair of spare eclipse glasses, taping it over your phone’s camera lens (or lenses), and securing the device in a tripod (or propping it up against a cup).
Don’t try to hold the phone, and use your phone’s shutter delay to decrease vibrations, says Gordon Telepun, an amateur enthusiast who has been photographing eclipses since 2001 and has advised NASA on how to capture them. “During totality, take the [eclipse glasses] filter off and take wide-angle shots of the corona in the sky and the landscape,” he says. “Automatic mode will work fine.”
Something smartphones are great at capturing is video of the moment the moon glides over the sun, says Benton: “That transition from daylight to nighttime is dramatic, and smartphones can handle that pretty well.”
Don’t be afraid to get creative
During the eclipse, there are plenty of other things to photograph besides the sun and moon. Foliage will create a natural version of a pinhole viewer, casting thousands of crescent images of the sun dancing around in the shade as the light streams through the trees.
Another natural phenomena is shadow bands—flickering gray ripples that appear on light-colored surfaces like sheets or the sides of houses within a few minutes of totality. “It’s almost like a stroboscopic effect,” Benton says, referring to the visual effect that makes objects appear as though they are moving more slowly than they actually are. “Videos of that could be interesting.”
“Take pictures of the faces of the people around you, too,” he adds. “Twenty years from now, your photo of the eclipse is going to be pretty much the same as anyone else’s. These other pictures are going to be a little more powerful in reminding you what your day was like.”
Take a moment to look around
Finally, when you’re looking up at the moon covering the sun during totality, let yourself enjoy the moment free from your technology. The next eclipse the US can expect to experience on this scale is in August 2044—so try hard to stay present.
“During totality, if you’re really concentrating on getting your photo, at some point let go of everything. Turn around—take a look with your eyes,” says Benton. “Whatever you’re seeing in the viewfinder or on the screen, it isn’t the same thing as seeing it with your own eyes. And it will change your life.”
When two black holes spiral inward and collide, they shake the very fabric of space, producing ripples in space-time that can travel for hundreds of millions of light-years. Since 2015, scientists have been observing these so-called gravitational waves to help them study fundamental questions about the cosmos, including the origin of heavy elements such as gold and the rate at which the universe is expanding.
But detecting gravitational waves isn’t easy. By the time they reach Earth and the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO), in Louisiana and Washington state, the ripples have dissipated into near silence. LIGO’s detectors must sense motions on the scale of one ten-thousandth the width of a proton to stand a chance.
LIGO has confirmed 90 gravitational wave detections so far, but physicists want to detect more, which will require making the experiment even more sensitive. And that is a challenge.
“The struggle of these detectors is that every time you try to improve them, you actually can make things worse, because they are so sensitive,” says Lisa Barsotti, a physicist at the Massachusetts Institute of Technology.
Nevertheless, Barsotti and her colleagues recently pushed past this challenge, creating a device that will allow LIGO’s detectors to detect far more black hole mergers and neutron star collisions. The device belongs to a growing class of instruments that use quantum squeezing—a practical way for researchers dealing with systems that operate by the fuzzy rules of quantum mechanics to manipulate those phenomena to their advantage.
Physicists describe objects in the quantum realm in terms of probabilities—for example, an electron is not located here or there but has some likelihood of being in each place, locking into one only when its properties are measured. Quantum squeezing can manipulate the probabilities, and researchers are increasingly using it to exert more control over the act of measurement, dramatically improving the precision of quantum sensors like the LIGO experiment.
“In precision sensing applications where you want to detect super-small signals, quantum squeezing can be a pretty big win,” says Mark Kasevich, a physicist at Stanford University who applies quantum squeezing to make more precise magnetometers, gyroscopes, and clocks with potential applications for navigation. Creators of commercial and military technology have begun dabbling in the technique as well: the Canadian startup Xanadu uses it in its quantum computers, and last fall, DARPA announced Inspired, a program for developing quantum squeezing technology on a chip. Let’s take a look at two applications where quantum squeezing is already being used to push the limits of quantum systems.
Taking control of uncertainty
The key concept behind quantum squeezing is the phenomenon known as Heisenberg’s uncertainty principle. In a quantum-mechanical system, this principle puts a fundamental limit on how precisely you can measure an object’s properties. No matter how good your measurement devices are, they will suffer a fundamental level of imprecision that is part of nature itself. In practice, that means there’s a trade-off. If you want to track a particle’s speed precisely, for example, then you must sacrifice precision in knowing its location, and vice versa. “Physics imposes limits on experiments, and especially on precision measurement,” says John Robinson, a physicist at the quantum computing startup QuEra.
By “squeezing” uncertainty into properties they aren’t measuring, however, physicists can gain precision in the property they want to measure. Theorists proposed using squeezing in measurement as early as the 1980s. Since then, experimental physicists have been developing the ideas; over the last decade and a half, the results have matured from sprawling tabletop prototypes to practical devices. Now the big question is what applications will benefit. “We’re just understanding what the technology might be,” says Kasevich. “Then hopefully our imagination will grow to help us find what it’s really going to be good for.”
LIGO is blazing a trail to answer that question, by enhancing the detectors’ ability to measure extremely tiny distances. The observatory registers gravitational waves with L-shaped machines capable of sensing tiny motions along their four-kilometer-long arms. At each machine, researchers split a laser beam in two, sending a beam down each arm to reflect off a set of mirrors. In the absence of a gravitational wave, the crests and troughs of the constituent light waves should completely cancel each other out when the beams are recombined. But when a gravitational wave passes through, it will alternately stretch and compress the arms so that the split light waves are slightly out of phase.
The resulting signals are subtle, though—so subtle that they risk being drowned out by the quantum vacuum, the irremovable background noise of the universe, caused by particles flitting in and out of existence. The quantum vacuum introduces a background flicker of light that enters LIGO’s arms, and this light pushes the mirrors, shifting them on the same scale as the gravitational waves LIGO aims to detect.
Barsotti’s team can’t get rid of this background flicker, but quantum squeezing allows them to exert limited control over it. To do so, the team installed a 300-meter-long cavity in each of LIGO’s two L-shaped detectors. Using lasers, they can create an engineered quantum vacuum, in which they can manipulate conditions to increase their level of control over either how bright the flicker can be or how randomly it occurs in time. Detecting higher-frequency gravitational waves is harder when the rhythm of the flickering is more random, while lower-frequency gravitational waves get drowned out when the background light is brighter. In their engineered vacuum, noisy particles still show up in their measurements, but in ways that don’t do as much to disturb the detection of gravitational waves.“ You can [modify] the vacuum by manipulating it in a way that is useful to you,” she explains.
The innovation was decades in the making: through the 2010s, LIGO incorporated incrementally more sophisticated forms of quantum squeezing based on theoretical ideas developed in the 1980s. With these latest squeezing innovations, installed last year, the collaboration expects to detect gravitational waves up to 65% more frequently than before.
Quantum squeezing has also improved precision in timekeeping. Working at the University of Colorado Boulder with physicist Jun Ye, a pioneer in atomic clock technology, Robinson and his team made a clock that will lose or gain at most a second in 14 billion years. These super-precise clocks tick slightly differently in different gravitational fields, which could make them useful for sensing how Earth’s mass redistributes itself as a result of seismic or volcanic activity. They could also potentially be used to detect certain proposed forms of dark matter, the hypothesized substance that physicists think permeates the universe, pulling on objects with its gravity.
The clock Robinson’s team developed, a type called an optical atomic clock, uses 10,000 strontium atoms. Like all atoms, strontium emits light at specific signature frequencies as electrons around the atom’s nucleus jump between different energy levels. A fixed number of crests and troughs in one of these light waves corresponds to a second in their clock. “You’re saying the atom is perfect,” says Robinson. “The atom is my reference.” The “ticking” of this light is far steadier than the vibrating quartz crystal in a wristwatch, for example, which expands and contracts at different temperatures to tick at different rates.
In practice, the tick in the Robinson team’s clock comes not from the light the electrons emit but from how the whole system evolves over time. The researchers first put each strontium atom in a “superposition” of two states: one in which the atom’s electrons are all at their lowest energy levels and another in which one of the electrons is in an excited state. This means each atom has some probability of being in either state but is not definitively in either one—similar to how a coin flipping in the air has some probability of being either heads or tails, but is neither.
Then they measure how many atoms are in each state. The act of measurement puts the atoms definitively in one state or the other, equivalent to letting the flipping coin land on a surface. Before they measure the atoms, even if they intend to wind up with a 50-50 mixture, they cannot precisely dictate how many atoms will end up in each state. That’s because in addition to the system’s change over time, there is also inherent uncertainty in the state of the individual atoms. Robinson’s team uses quantum squeezing to more reliably determine their final states by reducing these intrinsic fluctuations. Specifically, they manipulate the uncertainties in the direction of each atom’s spin, a property of many quantum particles that has no classical counterpart. Squeezing improved the clock’s precision by a factor of 1.5.
To be sure, gravitational waves and ultra-precise clocks are niche academic applications. But there is interest in adapting the approach to other, potentially more mainstream uses, including quantum computers, navigation, and microscopy.
The increased use of quantum squeezing is part of a wider technological trend toward higher precision—one that encompasses cramming more transistors on chips, studying the universe’s most elusive particles, and clocking the fleeting time it takes for an electron to leave a molecule. Squeezing benefits only measurements so subtle that the randomness of quantum mechanics contributes significant noise. But it turns out that physicists have more control than they think. They may not be able to remove the randomness, but they can engineer where it shows up.
More than 9,000 metric tons of human-made metal and machinery are orbiting Earth, including satellites, shrapnel, and the International Space Station. But a significant bulk of that mass comes from one source: the nearly a thousand dead rockets that have been discarded in space since the space age began.
Now, for the first time, a mission has begun to remove one of those dead rockets. Funded by the Japanese space agency JAXA, a spacecraft from the Japanese company Astroscale was launched on Sunday, February 18, by the New Zealand firm Rocket Lab and is currently on its way to rendezvous with such a rocket in the coming weeks. It’ll inspect it and then work out how a follow-up mission might be able to pull the dead rocket back into the atmosphere. If it succeeds, it could demonstrate how we could remove large, dangerous, and uncontrolled pieces of space junk from orbit—objects that could cause a monumental disaster if they collided with satellites or spacecraft.
“It cannot be overstated how important this is,” says Michelle Hanlon, a space lawyer at the University of Mississippi. “We have these ‘debris bombs’ just sitting up there waiting to be hit.”
There are an estimated 500,000 pieces of space junk as small as a centimeter across orbiting Earth, and about 23,000 trackable objects bigger than 10 centimeters. Dead rockets make up an interesting—and dangerous—category. The 956 known rocket bodies in space account for just 4% of trackable objects but nearly a third of the total mass. The biggest empty rockets, mostly discarded by Russia in the 1980s, 1990s, and 2000s, weigh up to nine tons—as much as an elephant.
These discarded upper stages, the top section of a rocket that boosts a satellite or spacecraft into its final orbit, are left to drift around our planet once the launch is complete. They are uncontrolled, spinning haphazardly, and pose a huge risk. If any two were to collide, they would produce a deadly cloud of up to “10,000 to 20,000 fragments,” says Darren McKnight, a space debris expert at the US debris tracking firm LeoLabs.
Such an event could happen at any moment. “At some point, I’d expect there to be a collision involving them,” says Hugh Lewis, a space debris expert at the University of Southampton in the UK. “There’s so much stuff out there.” That would pose a huge problem, rendering parts of Earth’s orbit unusable or, in a worst-case scenario, leading to a runaway chain reaction of collisions known as the Kessler syndrome. That could make some orbits unusable or even make human spaceflight too risky until the debris falls back into the atmosphere after decades to centuries.
Since 2007, when the United Nations introduced a new guideline that objects should be removed from space within 25 years of their operational lifetime, fewer rockets have been abandoned in orbit. Most upper stages now retain a bit of fuel to push themselves back into the atmosphere after launch. “They now tend to reserve some propellant to help them deorbit,” says Lewis. But thousands of “legacy objects” remain from before this rule was introduced, Lewis adds.
The rocket JAXA is targeting, as part of its Commercial Removal of Debris Demonstration (CRD2) program, is the upper stage of a Japanese H-IIA rocket that launched a climate satellite in 2009. Weighing three metric tons and as big as a bus, it orbits our planet at an altitude of 600 kilometers (373 miles). If left untended it will remain in orbit for decades, says Lewis, before the atmospheric drag of our planet is able to pull it back into the atmosphere. At that point it will burn up, with any remnants most likely falling into the ocean.
ADRAS-J’s mission is to figure out how to pull it back into the atmosphere before that happens. Sidling up to the rocket, the spacecraft will use cameras and sensors to inspect it from as near as a meter away. It will study the state of the rocket, including whether it is intact or if pieces have broken off and are drifting nearby, and also look for grapple points where a future spacecraft could attach.
“Designing a servicer to go up and grapple a three-ton piece of debris comes with a lot of challenges,” says Mike Lindsay, Astroscale’s chief technology officer. “The biggest challenge is dealing with the amount of uncertainty. The object has been up there for 15 years. It’s uncontrolled. We’re not communicating with it. So we don’t know how it’s moving, how it looks, and how it’s aged.”
Particularly crucial will be to determine whether, and if so how much, the rocket is spinning. Any rotation will need to be counteracted and stabilized before the rocket can then be pushed back into the atmosphere. The famous docking scene in the movie Interstellar, says Lewis, is “a perfect demonstration.”
ADRAS-J will spend the next few weeks investigating the rocket, and the inspection is expected to conclude by April. It is the first time a piece of derelict space debris will ever have been investigated in such a manner.
Japan has yet to pick the company that will conduct the second phase of the mission and actually remove the rocket from orbit, but Lindsay says Astroscale is ready, if it wins the contract. “We’re already testing some robotic capture methodologies that are compatible with the grapple points we’re going to inspect,” he says. “So it’s really important we get imagery of those interfaces.”
That mission will need to be much more substantial than ADRAS-J, says Lewis. To halt the rotation of the rocket and push it down into the atmosphere, any removal spacecraft would need to be almost as heavy as the rocket itself. “You need something equivalent [in mass] if you’re going to grab it,” he says. “If it’s tumbling end over end, you need a really capable system to manage that angular momentum.”
This is not the only effort at space debris removal taking place. In October 2023, the US Senate passed a bill to investigate removal technologies. The UK has selected both Astroscale and a Swiss firm, ClearSpace, to design missions to remove British space junk from orbit. And in 2026, ClearSpace plans to launch a mission for the European Space Agency (ESA) to remove from orbit a small piece of a European rocket, weighing about 112 kilograms (247 pounds).
“For missions after 2030, the ESA would foresee active removal to become mandatory,” says Holger Krag, the head of ESA’s Space Debris Office in Germany—that is, if a spacecraft has failed to remove itself from orbit with its own fuel.
It’s unclear exactly what shape the market for debris removal missions will take. While Japan is targeting one of its own dead rockets in good faith, tackling the daunting number of other dead rockets and satellites would be a costly endeavor. “Who’s going to pay for that?” says Lewis. “Removing one or two isn’t going to really make a dent in the problem. We need a sustained plan of removals.”
Legal hurdles abound, too. Russia and China, which have many of the largest dead rockets in orbit, are unlikely to let other countries remove their rockets for them, says Hanlon. “Private companies are not going to get permission from China or Russia to approach something that might have technological capabilities they do not want to share with the world,” she says.
There is also, currently, “no law that says you have to get your garbage out of orbit,” says Hanlon. While the UN does have its 25-year guideline, and national regulators such as the Federal Communications Commission in the US require satellites to be removed from orbit in as little as five years, empty rockets and legacy junk pose a whole other problem. “There’s no incentive to remediate,” says Hanlon.
Another option might be to reuse and recycle debris in orbit, including some of these dead rockets. Such an idea is untested at the moment, but could become viable as our operations in Earth orbit grow in the future. “Then we’re entering a different realm where there is an incentive—there is a market,” says Hanlon.
ADRAS-J, and whatever spacecraft follows in its footsteps, will demonstrate how we can start to tackle this problem. If we don’t, space junk “is just going to grow to the extent that we will not be able to launch anything,” says Hanlon. “The only way this cycle ends is to remove debris.”
We’ve known of Europa’s existence for more than four centuries, but for most of that time, Jupiter’s fourth-largest moon was just a pinprick of light in our telescopes—a bright and curious companion to the solar system’s resident giant. Over the last few decades, however, as astronomers have scrutinized it through telescopes and six spacecraft have flown nearby, a new picture has come into focus. Europa is nothing like our moon.
Observations suggest that its heart is a ball of metal and rock, surrounded by a vast saltwater ocean that contains more than twice as much water as is found on Earth. That massive sea is encased in a smooth but fractured blanket of cracked ice, one that seems to occasionally break open and spew watery plumes into the moon’s thin atmosphere.
For these reasons, Europa has captivated planetary scientists interested in the geophysics of alien worlds. All that water and energy—and hints of elements essential for building organic molecules —point to another extraordinary possibility. In the depths of its ocean, or perhaps crowded in subsurface lakes or below icy surface vents, Jupiter’s big, bright moon could host life.
“We think there’s an ocean there, everywhere,” says Bob Pappalardo, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “Essentially everywhere on Earth that there’s water, there’s life. Could there be life on Europa?”
Pappalardo has been at the forefront of efforts to send a craft to Europa for more than two decades. Now his hope is finally coming to fruition: later this year, NASA plans to launch Europa Clipper, the largest-ever craft designed to visit another planet. The $5 billion mission, scheduled to reach Jupiter in 2030, will spend four years analyzing this moon to determine whether it could support life. It will be joined after two years by the European Space Agency’s Juice, which launched last year and is similarly designed to look for habitable conditions, not only on Europa but also on other mysterious Jovian moons.
Neither mission will beam back a definitive answer to the question of extraterrestrial life. “Unless we get really lucky, we’re not going to be able to tell if there is life there, but we can find out if all the conditions are right for life,” says planetary geologist Louise Prockter at the Johns Hopkins Applied Physics Laboratory, a co-investigator on the Clipper camera team.
“Essentially everywhere on Earth that there’s water, there’s life. Could there be life on Europa?”
Bob Pappalardo, planetary scientist, NASA’s Jet Propulsion Laboratory
What these spacecraft will do is get us closer than ever before to answers, by identifying the telltale chemical, physical, and geological signatures of habitability—whether a place is a suitable environment for life to emerge and thrive.
The payoff for confirming these signs on Europa would be huge. Not because humans could settle on its surface—it’s far too harsh and rugged and cold and irradiated for our delicate bodies—but because it could justify future exploration to land there and look for alien life-forms. Finding something, anything, living on Europa would offer strong evidence for an alternate path through which life could emerge. It would mean that life on Earth is not exceptional. We’d know that we have neighbors close by—even if they’re microbial, which would be the most likely life-form—and that would make it very likely that we have neighbors elsewhere in the cosmos.
Engineers and technicians install reaction wheels on Europa Clipper at NASA’s Jet Propulsion Laboratory in California
NASA/JPL-CALTECH
“With the prospects of life—the prospects of vast oceans—within reach, you just have to go,” says Nicholas Makris, director of MIT’s Center for Ocean Engineering, who uses acoustics and other innovative methods to observe and explore big bodies of water. He once led a team of scientists who proposed a mission to land a spacecraft on Europa and use sound waves to explore what lies beneath the ice; he still hopes to see a lander go there one day. “You have to find out. Everyone wants to know,” he says. “There isn’t anyone who doesn’t want to know.”
From a spot in the sky to a dynamic moon
Long before it became the cosmic destination of the year, Europa played an outsize role in transforming our understanding of the solar system. That began with its discovery, when one night in January 1610, the Italian astronomer Galileo Galilei fixed his occiale—an ingenious homemade telescope—on Jupiter and noted three bright little dots near the side of the gas giant.
Galileo assumed it was an illusion, that they were distant stars that only appeared to be close. But the next night, he observed those same three bright little stars now on the other side of the planet. Further observations revealed yet another bright light, also wandering nearby but refusing to leave Jupiter’s side. In a short treatise called Sidereus Nuncius (Starry Messenger), published in March 1610, Galileo reported that he’d found four worlds orbiting Jupiter, similar to how Mercury and Venus orbit the sun. (Astronomers still regard Jupiter and its satellites as a kind of mini solar system.) Galileo named the worlds I, II, III, etc., and referred to them as the “Medicean planets,” though they’re now called the “Galilean moons.” His discovery was the first time scientists had directly observed small worlds orbiting something other than Earth or the sun, giving strong evidence to the argument, still controversial at the time, that planets circled the sun and not the other way around.
In 1614, German astronomer Simon Marius suggested that Jupiter’s four newly discovered moons be named Io (top), Callisto (middle), Ganymede (bottom), and Europa, after four “irregular loves” pursued by the god for whom the planet is named. Astronomers have since identified 91 others, and there are likely more.
NASA/JPL/UNIVERSITY OF ARIZONA (IO); NASA/JPL-CALTECH/KEVIN M. GILL (CALLISTO); NASA/JPL-CALTECH/SWRI/MSSS/KEVIN M. GILL (GANYMEDE¡)
Naming rights for these four Jovian moons ultimately went to the German astronomer Simon Marius, who claimed (but couldn’t prove) that he’d actually discovered them a few weeks before Galileo. In 1614, on a suggestion from Johannes Kepler, Marius proposed naming the moons Io, Callisto, Europa, and Ganymede—after four “irregular loves” pursued by Zeus (Jupiter) in ancient mythology. It took 200 years for those names to gain widespread adoption, but they were definitely an upgrade. Had Galileo’s naming scheme stuck, you’d now be reading about the “II Clipper,” which doesn’t have the same ring.
These moons were only the first to be discovered orbiting Jupiter. As of December 2023, astronomers had officially confirmed the existence of 91 others—and there are likely many more. Where the first four are round and follow stately, simple orbits, the more recent discoveries are more diverse. Some orbit in erratic swarms or go the opposite way around; some were asteroids captured in passing; others resulted from collisions. There are so many objects around Jupiter, in fact, that the International Astronomical Union no longer confers names on Jovian satellites unless they’re deemed to have significant scientific value.
The more we’ve learned about Europa, the more fascinating it has become. For centuries, it was little more than a spot appearing to move from one side of Jupiter to the other. But by the early 20th century, stargazers had made reasonable estimates of Europa’s diameter and mass (revealing that it was slightly smaller than Mercury or Earth’s moon, but larger than Pluto). They’d also studied the light reflecting from its surface and found that Europa was unexpectedly bright. Were it to replace our moon in the night sky, Europa would be a little smaller but shine five times brighter.
In the 1950s, when scientists began regarding distant objects not as bright cosmic curiosities but as real worlds, each with a distinct origin story, they began to ask questions about composition and formation. In The Planets, a book published in 1952, the astronomer Harold Urey suggested that water ice was abundant in the outer solar system because the bodies there formed far from the sun and never became warm enough for their ice to evaporate. By the 1960s, astronomers and astrophysicists had begun to speculate, partly on the basis of early measurements of its infrared spectrum, that Europa’s extraordinary reflectance was indeed due to the presence of ice. But proving it was difficult.
Stephen Ridgway, now an astronomer at the National Science Foundation’s NOIRLab in Tucson, Arizona, first heard about the problem of potentially icy moons in the outer solar system in the early 1970s, as a graduate student. Carl Pilcher, a postdoctoral researcher he’d met at a conference, told him about it. “We think they should have ice on them because they’re cold and reflective, but is it water? Is it carbon dioxide ice? Is it some other kind, or some mixture?” Ridgway recalls him asking.
It turned out that Ridgway, who describes himself as a tinkerer as well as a physicist, was well positioned to answer those questions. Using an old mathematical trick, he had devised an innovative instrument that could capture the spectrum of a distant light source, and he was using it during nighttime observations at a telescope at Kitt Peak Observatory, in Arizona. Every element and molecule absorbs and emits a unique collection of wavelengths of energy, and astronomers can read these spectra as fingerprints that reveal the composition of cosmic bodies. Pilcher suggested that he use the instrument to observe Europa.
They thought it would take a week to get a useful spectrum of one of Jupiter’s moons. “I went and got it in one night, maybe two,” Ridgway recalls. Ridgway showed the data to Pilcher, who showed it to his advisor, Tom McCord. Their analyses, published in Science in December 1972, suggested that water ice covered at least half, and possibly all, of the surface of Europa. (They also confirmed that the Jovian moons Ganymede and Callisto, both of which are larger than Europa, also had ice on their surfaces.)
In a 1980 paper, scientists reported that Europa looked “cracked like a broken eggshell” and compared it to a white pool ball fouled by a felt-tip pen.
One year later, the Pioneer 10 spacecraft, which had launched in March 1972, passed close enough to Europa to take a photo. The grainy image was provocative enough to justify sending Pioneer 11—which launched in 1973—to swing by on its way to Saturn and then out of the solar system.
Other potentially habitable locations in the solar system include two moons of Saturn: Titan (top) and Enceladus (bottom). Enceladus boasts liquid water beneath its surface and spews icy geysers into space. Titan has a surface rich in organic molecules and likely also has a liquid-water ocean beneath its crust.
NASA/JPL/UNIVERSITY OF ARIZONA/UNIVERSITY OF IDAHO (TITAN); NASA/JPL£CALTECH/SPACE SCIENCE INSTITUTE (ENCELADUS)
But Europa really started to come into focus in 1979, after the Voyager 2 spacecraft sped past the moon on July 9. (Voyager 1 also passed near Europa, but Voyager 2 had better photos.) The photographs the spacecraft beamed back revealed a smooth, bright surface, crisscrossed by long linear marks and low ridges; they might have been cracks or cliffs. In a 1980 NASA paper describing the observation, scientists reported that Europa looked “cracked like a broken eggshell” and compared it to a white pool ball fouled by a felt-tip pen. A 1983 Nature paper fueled interest in Europa by proposing that those features were consistent with liquid water and regular resurfacing, like the work of a natural Zamboni machine.
The Galileo mission, which launched in 1989 to study Jupiter’s atmosphere and the composition of Europa and other moons, encountered complications: the spacecraft’s primary antenna neglected to extend, which severely limited the data that could be transmitted to Earth.
But what did come back, after Galileo reached the system in 1995, further highlighted the moon’s extraordinary features and continues to energize scientists. “We have a lot of tantalizing glimpses of things,” Prockter says.
Among other things, Galileo’s magnetometer revealed a wildly varying magnetic field. Ice is a poor conductor, but liquid salt water isn’t, and Europa’s magnetic oscillations pointed to something moving beneath the surface. Its readings fit the idea of a global ocean being pushed, pulled, and heated by the tidal forces of Jupiter and its moon companions. They also lined up with earlier theoretical predictions of liquid water near the surface of icy moons. “We are pretty certain there’s an ocean there,” Prockter says, “but there is a chance that it might be something really exotic we don’t understand.” The only way to know for sure, she says, is to go back.
Other images from Galileo confirmed what telescope observations had long suggested: that Europa sports a youthful appearance despite its advanced age. It likely formed at the same time as Jupiter and the rest of the solar system, about 4.5 billion years ago, yet its surface—as dated by the oldest craters—is less than 100 million years old. “That’s a long time for us mere mortals,” says Prockter, “but in geological terms, it was born yesterday. The surface is very, very young.” The cracks and crevices on Europa suggest that giant ice plates on its surface collide, break apart, shove under and over each other, and refreeze.
The Pioneer 10 spacecraft, which launched in March 1972, passed close enough to take the first flyby photo
of Europa.
A photograph beamed
back by the Voyager 2
spacecraft, taken on the
morning of July 9, 1979,
illuminated Europa’s
mysterious nature in
better detail.
The Galileo mission, which launched in 1989 to study Jupiter’s atmosphere and the composition of its moons, including Europa, brought the moon’s extraordinary
features into focus.
This striking image of
Europa, captured in
September 2022 by a camera on the Juno spacecraft, reveals many of the features that are driving scientists to want to go back.
The longer scientists stared at Europa, the more mysteries emerged—like the questions around those ubiquitous dark ridges, often in pairs, that splatter the surface like a Jackson Pollock painting. Theorists have been busy devising explanations. Perhaps they’re made by ice volcanoes or geysers, or cracks where liquid water from subsurface pools rose, froze, and crumbled as the opening closed again. Maybe they resulted from subduction, which occurs on Earth in plate tectonics, as one giant sheet of ice slid and crumpled under another. “I’ve lost count of the number of different models for forming those landforms, but we really don’t know how they form,” Prockter says. “Part of the reason is that geology is based on Earth geology, but it’s not like Earth.”
One particularly striking image of Europa, captured in September 2022 by a camera on the Juno spacecraft, which is currently exploring Jupiter, reveals many of the features that are driving scientists to want to take a closer look. It shows the side of Europa that always faces Jupiter, bathed in sunlight. The moon’s surface is covered with cracks, streaks, and ridges where water may rise from the ocean beneath, or where irradiated surface material may sink lower. It also shows the “chaos terrains”—remarkably messy areas suggesting that giant pieces of ice have broken off, moved around, and refrozen, bolstering the case for geological activity similar to plate tectonics on Earth.
However, Juno’s brief two-hour flyby failed to answer questions about how those features formed or to confirm the existence of a buried ocean. For planetary scientists and astrophysicists, Clipper’s data can help fill in the missing knowledge. It will also push our relationship with Europa into new, unexplored territory.
What all those previous missions did do was help build enthusiasm for the plan to get to Europa, a plan that has evolved dramatically over the last 20 years. Originally, scientists wanted orbiters and landers, and NASA and ESA were working together on a joint mission with multiple spacecraft. Those plans fizzled, but in 2013—as a result of the 2011 Decadal Survey, a report that sets the priorities for space exploration for the next 10 years—NASA approved a plan to send an orbiter. By 2015, the agency had selected the instruments on board. Independently, the ESA moved forward with its own mission, with a broader goal of studying Jupiter’s icy moons.
“The Voyager mission transformed Europa from a light in the sky to a geologic world, and then the Galileo mission did the transformation to an ocean world,” says Diana Blaney, a JPL geophysicist who leads the Clipper team charged with using a mapping image spectrometer to identify molecules on Europa’s surface. “Hopefully, Clipper will bring the transformation to a habitable world.”
Getting in close
Researchers have long searched for signs of habitability in the solar system. Landers and rovers on Mars have found evidence of liquid water, mostly long gone, and organic molecules, which contain carbon, often in chains or rings. The building blocks of biological organisms—including nucleic acids and proteins—all contain carbon, which is why scientists get excited when they find organic molecules. Their presence could indicate that it’s possible for the precursors of life to form.
But it’s not enough just to have promising pieces in place. Any alien species would also have to find a way to grow and survive. That far from the sun, photosynthesis is likely impossible. Organisms would necessarily be fueled by chemical energy, much as microbial extremophiles near the black smokers and hydrothermal vents on the seafloor live off the minerals and methane.
The possibility for Europan life is at the mercy of the moon’s geophysics, says Lynnae Quick, a planetary geophysicist at NASA’s Goddard Space Flight Center. In fact, she argues that you can’t have one without the other. Europa seems to host the necessary ingredients for life. But ingredients alone, on Europa as in the kitchen, won’t spontaneously combine in the right way on their own. Other forces have to intervene: the moon needs to shift and squeeze, with heat, to mix the minerals from the seafloor with the salt water and any irradiated particles that seep down from the icy surface. “We need something to stir the pot, and I think the geophysical processes do that,” says Quick, whose graduate work on cryovolcanism in alien worlds led to her recruitment to join Clipper. She’s particularly excited about the possibility of finding pockets of warm salty water, trapped just beneath the surface, that could be abodes for life.
“Europa is my favorite body in the solar system,” Quick confesses. But she notes that other ocean worlds also offer promising places to look for signs of life. Those include Enceladus, a small moon of Saturn that, like Europa, has an icy crust with an ocean beneath. Images from the Cassini mission in 2005 revealed that geysers on the south pole of Enceladus spew water and organic molecules into space, feeding Saturn’s outermost ring.
However, Europa is bigger than Enceladus and is more likely to have a surface covered in icy plates that move in a way similar to Earth’s plate tectonics. This sort of activity would help combine the ingredients for life. Ganymede, another Jovian moon and the solar system’s largest, also likely has a liquid ocean, but sandwiched between two ice layers; without an interface between water and minerals, life is less probable. Other possible places to look include Titan, Saturn’s biggest moon, which also probably hides a liquid-water ocean beneath an ice crust. (Quick is an investigator on Dragonfly, a mission to explore Titan, scheduled to launch in 2028.)
Many of the challenges facing mission engineers
revolve around energy: Europa receives only a fifth as much sunlight as Earth. Clipper addresses the problem with gargantuan solar panels, spanning 30 meters when fully extended.
To look for the signs and signals of habitability, Clipper will use nine primary instruments. These will take pictures of the surface, look for water plumes, use ground-penetrating radar to measure the icy shell and search for the ocean below, and take precise measurements of the magnetic field.
The spacecraft will pass close enough to the moon to sample its thin atmosphere, and it will use mass spectrometry to identify molecules in the gases it finds there. Another instrument will enable scientists to analyze dust from the surface that has been kicked into the atmosphere by meteorite collisions. With any luck, they’ll be able to tell if that dust originated from below—from the enclosed ocean or subsurface lakes trapped in the ice—or from above, as fragments that migrated from the violent volcanoes on the nearby moon Io. Either scenario would be interesting to planetary geologists, but if the molecules were organic and came from below, they would help build the case that life could exist there.
ESA’s Juice mission has a similar suite of instruments, and scientists from the two teams meet regularly to plan for ways to jointly exploit the data when it starts coming in—five or six years from now. “This is really very good for scientists in the planetary community,” says Lorenzo Bruzzone, a telecommunications engineer at the University of Trento who leads the Juice mission’s radar tool team. He’s long been involved in efforts to get to Europa and the rest of the Jovian system.
Because Juice will visit the other ocean-bearing Galilean moons, Bruzzone says, data from that mission can be combined with Clipper’s to generate a more comprehensive picture of the geological processes and potential habitability of all the ocean worlds. “We can analyze the differences in subsurface geology to better understand the evolution of the Jupiter system,” he says. Those differences may help explain, for example, why three of the Galilean moons formed as icy worlds while the fourth, Io, became a volcanic hellscape.
Jupiter’s radiation has the potential to interfere with every measurement, turning a meaningful signal into a mess of digital snow, like static on a television screen.
To make sure those instruments work when they get there, engineers and designers for both missions have had to contend with a raft of challenges. Many of them revolve around energy: Europa receives only a fifth as much sunlight as Earth. Clipper addresses the problem with gargantuan solar panels, which will span 30 meters when fully extended. (An earlier proposal for a mission to Europa included nuclear batteries, but that idea was expensive, and it was ultimately scrapped.)
In addition, Jupiter’s magnetic field is more than 10,000 times more powerful than Earth’s, accelerating already-energetic particles around the planet to create an intense radiation environment. The radiation has the potential to interfere with every measurement—turning a meaningful signal into a mess of digital snow, like static on a television screen—and can threaten the integrity of the instruments.
To slow the accumulation of radiation damage, Clipper won’t orbit Europa when it reaches the moon in 2030; instead, it will make about 50 flybys over four years, swooping nearer and farther from the destructive radiation field. At its closest, it will pass just 16 miles above the surface. The name points back to fast 19th-century sailing vessels, but it also describes the journey. The craft will sail past the world, over and over. In between passes, its distance from Jupiter will give it openings to transmit data back to Earth.
Those first transmissions will have been generations—if not centuries—in the making. Some of the people who laid the groundwork for the mission, decades ago, have already died. Makris, at MIT, says that when scientists were first discussing how to get to Europa, he was told by Ron Greeley, a planetary geologist and NASA advisor who proposed and fiercely advocated for missions to the moon, that space travel spans generations: “He likened it to building a cathedral.” Prockter notes that by the time Clipper’s data comes in, she’ll be in her late 60s. “I will have spent my entire career on Clipper,” Prockter says. Quick, at 39, is one of the youngest members of the science team.
In April 2023, the European Space Agency
launched Juice to explore several ocean-bearing moons of Jupiter. In July 2032, it will fly 400 kilometers above Europa’s surface, twice.
ESA/ATG MEDIALAB
Many of the scientists involved in Clipper—including Pappalardo, Prockter, and Quick—are already planning ways to use its insights for future missions to other worlds. But it’s Europa that holds the most promise, at least for the moment.
Pappalardo thrills at the prospect of finding a Europan neighborhood that might be just right for life. “What if we find a place that’s kind of an oasis, where there are hot spots or warm spots that we detect with a thermal imager?” he says.
Ultimately, Pappalardo says, his hope is that Clipper finds enough evidence to make a strong case for sending a lander someday. The mission’s observations could also tell scientists where to land it: “That would be a place where we’d say, well, we really need to go and scoop up some of that stuff from below the surface, look at it with a microscope, put it in a mass spectrometer, and do the next step, which is to search for life.”
Stephen Ornes is a science writer based in Nashville, Tennessee.
Why isn’t the universe boring? It could be. The number of subatomic particles in the universe is about 1080, a 1 with 80 zeros after it. Scatter those particles at random, and the universe would just be a monotonous desert of sameness, a thin vacuum without any structure much larger than an atom for billions of light-years in any direction. Instead, we have a universe filled with stars and planets, canyons and waterfalls, pine trees and people. There is an exuberant plenty to nature. But why is any of this stuff here?
Cosmologists have pieced together an answer to this question over the past half-century, using a variety of increasingly complex experiments and observational instruments. But as is nearly always the case in science, that answer is incomplete. Now, with new experiments of breathtaking sensitivity, physicists are hoping to spot a never-before-seen event that could explain one of the great remaining mysteries in that story: why there was any matter around to form complicated things in the first place.
The interestingness of the world around us is all the more puzzling when you look at the universe on the largest scales. You find structured clumpiness for a while. Stars form galaxies, galaxies form galaxy clusters, and those clusters form superclusters and filaments and walls around great cosmic voids nearly empty of matter.
But when you zoom out even further, looking at chunks of the universe more than 300 million light-years wide, all that structure fades away. Past this point, the light from all the stars in the cosmos merges into an indistinct blur, and the universe does indeed look quite boringly similar in all directions, with no features or differences of note anywhere. Cosmologists call this the “end of greatness.”
This tedious cosmic landscape exists because the universe really was boring once. Shortly after the Big Bang, and for hundreds of thousands of years after that, it was relentlessly dull. All that existed was a thick red-hot haze of particles, stretching for trillions upon trillions of kilometers and filling every point in the universe almost evenly, with minuscule differences in the density of matter between one spot and another.
But as the universe expanded and cooled, gravity amplified those tiny differences. Slowly, over the following millions and billions of years, the places in the universe with slightly more stuff attracted even more stuff. And that’s where we came from—the profusion of things in the universe today eventually arose as more and more material accumulated, making those slightly over-dense regions into radically complicated places packed with enough matter to form stars, galaxies, and us. On the very largest scales, boredom still reigns, as it has since the beginning of time. But down here in the dirt, there’s ample variety.
This story still has some holes. For one thing, it is not clear where the matter came from in the first place. Particle physics demands that anything that creates matter must also create an equal amount of antimatter, carefully conserving the balance between the two. Every kind of matter particle has an antimatter twin that behaves like matter in nearly every way. But when a matter particle comes into contact with its antimatter counterpart, they annihilate each other, disappearing and leaving behind nothing but radiation.
That’s exactly what happened right after the Big Bang. Matter and antimatter annihilated, leaving our universe aglow with radiation—and a small amount of leftover matter, which had slightly exceeded the amount of antimatter at the start. This tiny mismatch made the difference between the universe we have today and an eternity of tedium, and we don’t know why it happened. “Somehow there was this little imbalance and it turned into everything—namely, us. I really care about us,” says Lindley Winslow, an experimental particle physicist at MIT. “We have a lot of questions about the universe and how it evolved. But this is a pretty basic kindergarten sort of question of, okay, why are we here?”
Caught in the act
To answer this question, Winslow and other physicists around the world have constructed several experiments to catch nature in the act of violating the balance between matter and antimatter. They hope to see that violation in the form of neutrinoless double-beta decay, a type of radioactive decay. At the moment, that process is theoretical—it may not happen at all. But if it does, it would provide a possible explanation for the imbalance between matter and antimatter in the early universe.
That explanation would rely on neutrinos, the ghostly oddballs of particle physics. These lightweight specters whiz about the universe, barely interacting with anything. Trillions of neutrinos are constantly streaming through every square centimeter of your body and the entire planet Earth, ignoring you just as completely as they ignore the iron core of our planet. Reliably stopping just one neutrino would take a slab of lead a light-year thick.
And neutrinos might perform an even more bizarre trick. The neutrino and its antimatter partner could be one and the same, making it different from every other known form of matter and capable of annihilating itself. “If we observed [neutrinoless double-beta decay], it would prove that the neutrino is its own antiparticle,” says Winslow. “It would also provide us a process that makes more matter than antimatter.”
That process starts in the heart of the atom. When some unstable atomic nuclei decay, they emit an electron along with an antineutrino to counterbalance it: one particle of matter and one of antimatter. This is a very common kind of radioactive decay, known for historical reasons as beta decay. Significantly less common is double-beta decay, when an atomic nucleus emits two electrons at once, along with two antineutrinos to balance them out.
Double-beta decay is “one of the longest processes that we’ve ever measured,” says Winslow. To see a single atom undergo double-beta decay, she continues, we would typically have to wait a billion times longer than the current age of the universe. But if the neutrino is its own antiparticle, there’s the possibility of something even more rare than that: a double-beta decay where the two neutrinos annihilate each other immediately, leaving only the two electrons without any antimatter to counterbalance them. This is neutrinoless double-beta decay.
Spotting such a rare process would be difficult—but not impossible, thanks to the phenomenally huge number of atoms in objects of everyday size. There are nearly a trillion trillion atoms in a few grams of material. “So if you just pile up a bunch of stuff, you just have the possibility of seeing something that happens in timelines even longer than the age of the universe,” says Winslow.
This is the approach taken by the Cryogenic Underground Observatory for Rare Events (CUORE, Italian for “heart”), a detector under a mountain in Italy that is waiting for evidence of neutrinoless double-beta decay. A certain isotope of tellurium is one of the nuclei susceptible to double-beta decay. CUORE watches for it in a set of 988 five-centimeter-wide cubic crystals of tellurium dioxide, each connected to a highly sensitive thermometer. The combined energy of the two electrons emitted in neutrinoless double-beta decay is the same every time, so if the decay occurs anywhere within one of these crystals, that specific amount of energy will be deposited into the crystal as heat, raising its temperature by one ten-thousandth of a degree Celsius.
But a signal that small is hard to see against all the other things that could change the temperature of a crystal. That’s why CUORE is under a mountain—the bulk of the rock above it shields it from nearly all cosmic rays. And that’s also why CUORE needs to be kept phenomenally cold, just a few thousandths of a degree above absolute zero—it “wins the award for coldest cubic meter in the known universe,” says Winslow. The sensors are so exquisitely sensitive that they can even pick up vibrations from waves crashing on the beach, 60 kilometers away.
CUORE isn’t alone. There are other experiments looking for neutrinoless double-beta decay, including KamLAND-Zen, an experiment—also under a mountain—in Japan, using gaseous xenon in place of tellurium crystals. But none of the experiments searching for the decay have seen it yet, despite years of waiting. There are plans to upgrade the sensors at CUORE and increase the number of crystals being used; there are also plans to increase the size and sensitivity of KamLAND-Zen. But the future of these experiments is uncertain.
“In principle, we could make bigger, better experiments,” says Reina Maruyama, a physicist at Yale who is also part of the CUORE collaboration. “You could make 10 of what we have. And so I think it just becomes a matter of how much resources humankind wants to put into this experiment.” Winslow estimates that a full search would require two more rounds of improvements to existing experiments. If those are done and they come up empty-handed, she says, “then we will have pretty much eliminated the possibility of the neutrino being its own antiparticle.”
If that happens, it’s the end of a promising theory, but not the end of the search. Physicists have plenty of other ideas about how matter and antimatter could have become imbalanced. But finding evidence for those ideas is hard. Some could be confirmed if the Large Hadron Collider, the largest particle collider in the world, finds something unexpected over the next few years; other theories depend on sensitive searches for dark matter, an invisible and hypothetical substance, strongly suggested by decades of evidence, which is believed to constitute more than 80% of the matter in the universe.
And some theories exact a high price for explaining the imbalance: they suggest that protons, one of the key components of atomic nuclei, are unstable. These theories say that proton decay takes even longer than neutrinoless double-beta decay, on average about a trillion trillion times longer than the current age of the universe. Super-Kamiokande (aka “Super-K”), in Japan, is the largest experiment watching for proton decay, using an underground vat of 50,220 metric tons of ultra-pure water surrounded by 13,031 light sensors. At the limits of knowledge, Super-K waits for a faint flash in the darkness. It has yet to catch a proton in the act.
But whatever caused the matter-antimatter imbalance in the early universe, there’s one thing that physicists are sure of: eventually, the show will end. Over time, all interesting structures will fade away as the universe’s matter and energy are scattered about increasingly at random. Eons from now, this will lead once more to a fully featureless void—and this time, it will be far less dense and far more uniform than the primordial haze. This state, known as heat death, is likely to be the final fate of the universe, myriad quadrillions of years in the future.
So we’re lucky—we live at a time when the universe is filled with complexity and beauty, even if we don’t fully understand why.
Adam Becker is a freelance journalist based in Berkeley, California. He has written for the New York Times, the BBC, Scientific American, Quanta, New Scientist, and other outlets. He is also the author of What Is Real?, an affable account of the sordid untold history of quantum physics.
Egbert Edelbroek was acting as a sperm donor when he first wondered whether it’s possible to have babies in space.
Curious about the various ways that donated sperm can be used, Edelbroek, a Dutch entrepreneur, began to speculate on whether in vitro fertilization technology was possible beyond Earth—or could even be improved by the conditions found there. Could the weightlessness of space be better than a flat laboratory petri dish?
Now Edelbroek is CEO of SpaceBorn United, a biotech startup seeking to pioneer the study of human reproduction away from Earth. Next year, he plans to send a mini lab on a rocket into low Earth orbit, where in vitro fertilization, or IVF, will take place. If it succeeds, Edelbroek hopes his work could pave the way for future space settlements.
“Humanity needs a backup plan,” he says. “If you want to be a sustainable species, you want to be a multiplanetary species.”
Beyond future space colonies, there is also a more pressing need to understand the effects of space on the human reproductive system. No one has ever become pregnant in space—yet. But with the rise of space tourism, it’s likely that it will eventually happen one day. Edelbroek thinks we should be prepared.
Despite the burgeoning interest in deep space exploration and settlement, prompted in part by billionaires such as Elon Musk and Jeff Bezos, we still know very little about what happens to our reproductive biology when we’re in orbit. A report released in September by the US National Academies of Science, Engineering, and Medicine points out that almost no research has been done on human reproduction in space, adding that our understanding of how space affects reproduction is “vital to long-term space exploration, but largely unexplored to date.”
Some studies on animals have suggested that the various stages of reproduction—from mating and fertilization to embryo development, implantation, pregnancy, and birth—can function normally in space. For example, in the very first such experiment, eight Japanese medaka fish developed from egg to hatchling aboard the space shuttle Columbia in 1994. All eight survived the return to Earth and seemed to behave normally.
Taking it step by step
Yet other studies have found evidence that points to potential problems. Pregnant rats that spent much of their third trimester—a total of five days—on a Soviet satellite in 1983 experienced complications during labor and delivery. Like all astronauts returning to Earth, the rats were exhausted and weak. Their deliveries lasted longer than usual, likely because of atrophied uterine muscles. All the pups in one of the litters died during delivery, the result of an obstruction thought to be due in part to the mother’s weakened state.
To Edelbroek, these inconclusive results point to a need to systematically isolate each step in the reproductive process in order to better understand how it is affected by conditions like lower gravity and higher radiation exposure. The mini lab his company developed is designed to do exactly that. It is about the size of a shoebox and uses microfluidics to connect a chamber containing sperm to a chamber containing an egg. It can also rotate at different speeds to replicate the gravitational environment of Earth, the moon, or Mars. It is small enough to fit inside a capsule that can be housed on top of a rocket and launched into space.
The mini lab disc will use microfluidics to fertilize an egg.
MARTA FERRAZ
After the egg has been fertilized in the device, it splits into two cells, each of which divides again to form four cells and so on. After five to six days, the embryo reaches a stage known as a blastocyst, which looks like a hollow ball. At this point, the embryos in the mini lab will be cryogenically frozen for their return to Earth.
But first, SpaceBorn needs to demonstrate that the device works in space. Edelbroek’s plans to test it were revealed at the SXSW festival in March this year.
“We have our first prototype finished, and it’s going to go on board a rocket this year—within six months,” he told the audience.
That turned out to be overly optimistic. During a Zoom meeting of the SpaceBorn United advisory board in August, Edelbroek explained that a company that had been contracted to perform the launch in Iceland had not yet secured the necessary launch permits. Edelbroek decided to scrub the suborbital test and is now targeting a loftier goal—a three-hour orbital test of the device with the German startup Atmos Space Cargo, tentatively scheduled for November 2024.
“You want to find this stuff out in a petri dish before you’ve got tourists getting pregnant in space.”
If it is able to pull off this test, SpaceBorn United plans to move forward with additional test flights following the plan for its mission, known as ARTIS (Assisted Reproductive Technology in Space). As described on its website, the first few ARTIS missions will involve rodent embryos fertilized in space using simulated gravity equivalent to that on Earth. Next, the embryos that were formed in space and cryogenically frozen for their return to Earth will be implanted into a rodent mother. If this results in the birth of healthy pups, later ARTIS missions will include human embryos fertilized under Earth-like gravity and, eventually, partial gravity similar to that of the moon or Mars.
If these experiments show that human embryos can be formed under those low-gravity conditions, Edelbroek believes, it would be a major advance toward demonstrating the feasibility of multigenerational space settlements.
“I feel like we definitely need this kind of research to be done,” says Kelly Weinersmith, a biologist and coauthor of a forthcoming book about space settlement titled A City on Mars. “I do feel like it’s worth making humans multiplanetary as, like, a plan B,” she says. “But I think we need to do it slowly.”
Edelbroek also sees a more immediate need for the research. As access to space expands, and especially as the space tourism industry grows, it becomes increasingly likely that a baby could be conceived in space, intentionally or otherwise. Currently, there is very little understanding of how a space pregnancy could affect either the mother or the unborn child. Edelbroek sees the company’s IVF studies as urgently needed to help inform such risks.
Edelbrook with the Independence Aerospace capsule during the SXSW conference where he announced his plan.
SCOTT SOLOMON
Weinersmith agrees. “You want to find this stuff out in a petri dish before you’ve got tourists getting pregnant in space,” she says.
Currently, SpaceBorn United is among only a handful of research groups working on reproduction in space. That is largely because there has been very little public funding available for the research. NASA, the European Space Agency, and other governmental organizations have historically been reluctant to fund and support research on sex and human reproduction.
Erik Antonsen, an associate professor of space medicine at Baylor College of Medicine and a consultant for NASA’s Human Research Program, sees yet another obstacle: the relatively small amount of funding that has historically gone to space medical research. “The Human Research Program at NASA … they have an entire budget of like $130 million. Which is crap,” he says. “And that’s the premier research group and funding that are out there.”
More money needed
The National Academies report could change that. Among the recommendations is a tenfold increase in funding for biological and physical sciences, including studies on reproduction. According to Robert Ferl, cochair of the group that produced the report, that research should include studies on reproduction in a variety of different organisms, from plants to people, because many of the underlying biological principles are the same.
“We’ve got to know what happens over generations, because there are fundamental processes involved when an egg is produced, when sperm is produced, and when the new zygote—no matter what organism it is—begins to grow and develop,” he says.
But there is no guarantee that the funding recommended in the report will materialize. In the meantime, SpaceBorn United is pressing forward with its plans for testing an IVF lab in low Earth orbit. It would be “a wonderful experiment if you can get the funding for it,” says Antonsen.
Edelbroek says he has raised $400,000 so far from venture capitalists and assembled an advisory board that includes fertility experts and engineers. But any money raised will be spent by the end of the year, and he now has to raise enough for the first planned orbital test next year. Assuming the extra funds come through, which is by no means certain, Jeffrey Alberts, a professor at Indiana University who has studied the effects of spaceflight on rodents, is optimistic. “I’ve come to the general conclusion that fertilization [in space] will probably work,” he says.
Yet even if fertilization is successful, the embryos still have to get back to Earth. That part worries Dorit Donoviel, director of the Translational Research Institute for Space Health at Baylor College of Medicine.
“Those blastocysts are going to experience massive g-loads coming back,” she says.
Marta Ferraz, who leads research and mission design for SpaceBorn United, acknowledges the challenge.
“Reentry is a really difficult process technologically,” she says. SpaceBorn United recently began testing its prototype to measure the forces to which the samples will be subjected. The results of a recent high-altitude drop test are still pending, but the team is confident the device can be stabilized enough to minimize the impact on the embryos.
This information will be essential in order to get approval to use live embryos. The approval process also requires permission from the nation in which the launch company is based—and the way to obtain it varies according to whether the entity conducting the research is public or private.
Donoviel sees this as a loophole that needs to be fixed. She was one of 25 coauthors on a recent opinion piece published in Science that argued for more stringent and consistent guidelines for research in the commercial space industry. They stated that “companies should issue policies and develop best practices to ensure that sponsored research is performed in a socially responsible and ethical manner.”
Of particular concern to Donoviel are SpaceBorn United’s long-term plans to conduct IVF experiments in space using human embryos. Donoviel considers this unethical and worries that it could turn public opinion against all types of space research.
“It extends a negative aura over our entire industry and field, so I’m very much against this work,” she says.
Edelbroek argues that his company is taking ethical concerns very seriously. He told me that it recently added two advisors who specialize in biomedical ethics. He added that despite being a privately funded company, SpaceBorn United intends to follow all the internationally recognized legal and ethical standards when it comes to applying for permission to use human embryos.
But experiments on reproduction do not necessarily need to involve human samples. Jeffrey Alberts wants to see several generations of animals like rats be born in space, live their entire lives there, and reproduce. Such experiments have never been performed and would be the definitive test of whether there are any multigenerational effects of life in space—an outstanding question highlighted by the National Academies report.
The results of such studies would reveal a lot about whether space settlements could ever become a reality. But to Edelbroek, the fact that multigenerational studies on animals have never been approved is the raison d’être for his company. And while its research might make some people uncomfortable, he sees pushing the boundaries as important.
“Humanity has benefited all the time from expanding her comfort zone,” he says. “And if you ask me, it’s good to continue to do that into space.”
Egbert Edelbroek was acting as a sperm donor when he first wondered whether it’s possible to have babies in space.
Curious about the various ways that donated sperm can be used, Edelbroek, a Dutch entrepreneur, began to speculate on whether in vitro fertilization technology was possible beyond Earth—or could even be improved by the conditions found there. Could the weightlessness of space be better than a flat laboratory petri dish?
Now Edelbroek is CEO of SpaceBorn United, a biotech startup seeking to pioneer the study of human reproduction away from Earth. Next year, he plans to send a mini lab on a rocket into low Earth orbit, where in vitro fertilization, or IVF, will take place. If it succeeds, Edelbroek hopes his work could pave the way for future space settlements.
“Humanity needs a backup plan,” he says. “If you want to be a sustainable species, you want to be a multiplanetary species.”
Beyond future space colonies, there is also a more pressing need to understand the effects of space on the human reproductive system. No one has ever become pregnant in space—yet. But with the rise of space tourism, it’s likely that it will eventually happen one day. Edelbroek thinks we should be prepared.
Despite the burgeoning interest in deep space exploration and settlement, prompted in part by billionaires such as Elon Musk and Jeff Bezos, we still know very little about what happens to our reproductive biology when we’re in orbit. A report released in September by the US National Academies of Science, Engineering, and Medicine points out that almost no research has been done on human reproduction in space, adding that our understanding of how space affects reproduction is “vital to long-term space exploration, but largely unexplored to date.”
Some studies on animals have suggested that the various stages of reproduction—from mating and fertilization to embryo development, implantation, pregnancy, and birth—can function normally in space. For example, in the very first such experiment, eight Japanese medaka fish developed from egg to hatchling aboard the space shuttle Columbia in 1994. All eight survived the return to Earth and seemed to behave normally.
Taking it step by step
Yet other studies have found evidence that points to potential problems. Pregnant rats that spent much of their third trimester—a total of five days—on a Soviet satellite in 1983 experienced complications during labor and delivery. Like all astronauts returning to Earth, the rats were exhausted and weak. Their deliveries lasted longer than usual, likely because of atrophied uterine muscles. All the pups in one of the litters died during delivery, the result of an obstruction thought to be due in part to the mother’s weakened state.
To Edelbroek, these inconclusive results point to a need to systematically isolate each step in the reproductive process in order to better understand how it is affected by conditions like lower gravity and higher radiation exposure. The mini lab his company developed is designed to do exactly that. It is about the size of a shoebox and uses microfluidics to connect a chamber containing sperm to a chamber containing an egg. It can also rotate at different speeds to replicate the gravitational environment of Earth, the moon, or Mars. It is small enough to fit inside a capsule that can be housed on top of a rocket and launched into space.
The mini lab disc will use microfluidics to fertilize an egg.
MARTA FERRAZ
After the egg has been fertilized in the device, it splits into two cells, each of which divides again to form four cells and so on. After five to six days, the embryo reaches a stage known as a blastocyst, which looks like a hollow ball. At this point, the embryos in the mini lab will be cryogenically frozen for their return to Earth.
But first, SpaceBorn needs to demonstrate that the device works in space. Edelbroek’s plans to test it were revealed at the SXSW festival in March this year.
“We have our first prototype finished, and it’s going to go on board a rocket this year—within six months,” he told the audience.
That turned out to be overly optimistic. During a Zoom meeting of the SpaceBorn United advisory board in August, Edelbroek explained that a company that had been contracted to perform the launch in Iceland had not yet secured the necessary launch permits. Edelbroek decided to scrub the suborbital test and is now targeting a loftier goal—a three-hour orbital test of the device with the German startup Atmos Space Cargo, tentatively scheduled for November 2024.
“You want to find this stuff out in a petri dish before you’ve got tourists getting pregnant in space.”
If it is able to pull off this test, SpaceBorn United plans to move forward with additional test flights following the plan for its mission, known as ARTIS (Assisted Reproductive Technology in Space). As described on its website, the first few ARTIS missions will involve rodent embryos fertilized in space using simulated gravity equivalent to that on Earth. Next, the embryos that were formed in space and cryogenically frozen for their return to Earth will be implanted into a rodent mother. If this results in the birth of healthy pups, later ARTIS missions will include human embryos fertilized under Earth-like gravity and, eventually, partial gravity similar to that of the moon or Mars.
If these experiments show that human embryos can be formed under those low-gravity conditions, Edelbroek believes, it would be a major advance toward demonstrating the feasibility of multigenerational space settlements.
“I feel like we definitely need this kind of research to be done,” says Kelly Weinersmith, a biologist and coauthor of a forthcoming book about space settlement titled A City on Mars. “I do feel like it’s worth making humans multiplanetary as, like, a plan B,” she says. “But I think we need to do it slowly.”
Edelbroek also sees a more immediate need for the research. As access to space expands, and especially as the space tourism industry grows, it becomes increasingly likely that a baby could be conceived in space, intentionally or otherwise. Currently, there is very little understanding of how a space pregnancy could affect either the mother or the unborn child. Edelbroek sees the company’s IVF studies as urgently needed to help inform such risks.
Edelbrook with the Independence Aerospace capsule during the SXSW conference where he announced his plan.
SCOTT SOLOMON
Weinersmith agrees. “You want to find this stuff out in a petri dish before you’ve got tourists getting pregnant in space,” she says.
Currently, SpaceBorn United is among only a handful of research groups working on reproduction in space. That is largely because there has been very little public funding available for the research. NASA, the European Space Agency, and other governmental organizations have historically been reluctant to fund and support research on sex and human reproduction.
Erik Antonsen, an associate professor of space medicine at Baylor College of Medicine and a consultant for NASA’s Human Research Program, sees yet another obstacle: the relatively small amount of funding that has historically gone to space medical research. “The Human Research Program at NASA … they have an entire budget of like $130 million. Which is crap,” he says. “And that’s the premier research group and funding that are out there.”
More money needed
The National Academies report could change that. Among the recommendations is a tenfold increase in funding for biological and physical sciences, including studies on reproduction. According to Robert Ferl, cochair of the group that produced the report, that research should include studies on reproduction in a variety of different organisms, from plants to people, because many of the underlying biological principles are the same.
“We’ve got to know what happens over generations, because there are fundamental processes involved when an egg is produced, when sperm is produced, and when the new zygote—no matter what organism it is—begins to grow and develop,” he says.
But there is no guarantee that the funding recommended in the report will materialize. In the meantime, SpaceBorn United is pressing forward with its plans for testing an IVF lab in low Earth orbit. It would be “a wonderful experiment if you can get the funding for it,” says Antonsen.
Edelbroek says he has raised $400,000 so far from venture capitalists and assembled an advisory board that includes fertility experts and engineers. But any money raised will be spent by the end of the year, and he now has to raise enough for the first planned orbital test next year. Assuming the extra funds come through, which is by no means certain, Jeffrey Alberts, a professor at Indiana University who has studied the effects of spaceflight on rodents, is optimistic. “I’ve come to the general conclusion that fertilization [in space] will probably work,” he says.
Yet even if fertilization is successful, the embryos still have to get back to Earth. That part worries Dorit Donoviel, director of the Translational Research Institute for Space Health at Baylor College of Medicine.
“Those blastocysts are going to experience massive g-loads coming back,” she says.
Marta Ferraz, who leads research and mission design for SpaceBorn United, acknowledges the challenge.
“Reentry is a really difficult process technologically,” she says. SpaceBorn United recently began testing its prototype to measure the forces to which the samples will be subjected. The results of a recent high-altitude drop test are still pending, but the team is confident the device can be stabilized enough to minimize the impact on the embryos.
This information will be essential in order to get approval to use live embryos. The approval process also requires permission from the nation in which the launch company is based—and the way to obtain it varies according to whether the entity conducting the research is public or private.
Donoviel sees this as a loophole that needs to be fixed. She was one of 25 coauthors on a recent opinion piece published in Science that argued for more stringent and consistent guidelines for research in the commercial space industry. They stated that “companies should issue policies and develop best practices to ensure that sponsored research is performed in a socially responsible and ethical manner.”
Of particular concern to Donoviel are SpaceBorn United’s long-term plans to conduct IVF experiments in space using human embryos. Donoviel considers this unethical and worries that it could turn public opinion against all types of space research.
“It extends a negative aura over our entire industry and field, so I’m very much against this work,” she says.
Edelbroek argues that his company is taking ethical concerns very seriously. He told me that it recently added two advisors who specialize in biomedical ethics. He added that despite being a privately funded company, SpaceBorn United intends to follow all the internationally recognized legal and ethical standards when it comes to applying for permission to use human embryos.
But experiments on reproduction do not necessarily need to involve human samples. Jeffrey Alberts wants to see several generations of animals like rats be born in space, live their entire lives there, and reproduce. Such experiments have never been performed and would be the definitive test of whether there are any multigenerational effects of life in space—an outstanding question highlighted by the National Academies report.
The results of such studies would reveal a lot about whether space settlements could ever become a reality. But to Edelbroek, the fact that multigenerational studies on animals have never been approved is the raison d’être for his company. And while its research might make some people uncomfortable, he sees pushing the boundaries as important.
“Humanity has benefited all the time from expanding her comfort zone,” he says. “And if you ask me, it’s good to continue to do that into space.”
