Britney Schmidt grabs the worn-out silver skull atop the stick shift of her 1977 Datsun 280Z and speeds south onto I-35 out of Austin, Texas. The roaring engine momentarily drowns out the heavy metal cranking through the stereo, but Schmidt eagerly talks over them both. The 30-year-old planetary scientist has many passions, from the social commentary of Dostoyevsky to the lyrics of Metallica, but none measure up to her obsession with alien life. Although the kind of aliens she seeks are rather unsexy—perhaps nothing more than floating microbes—their discovery would be staggering. If life can arise independently on two worlds, she knows, it is likely to be ubiquitous through the universe.
To harbor life, an extraterrestrial world must satisfy three basic requirements. First, it must have a consistent source of sufficient energy. Second, it needs the right ingredients: a substantial collection of molecules such as hydrogen peroxide or sulfur dioxide, which play vital roles in the chemical reactions that form the foundation of life. Finally, it must have water. So where can you find all three?
As Schmidt’s electric-blue Datsun, nicknamed Zorro, settles into the highway’s middle lane, she quickly dismisses a few popular suggestions. Many scientists favor Saturn’s moon Titan, which has lakes of methane, an organic molecule that can give rise to life’s building blocks. “Maybe,” Schmidt says. “Compelling chemistry. But where’s the energy?” It is not clear whether Titan has enough heat to support life. Mars is only marginally better. “It probably had life at one time, but again, where’s the energy?” she asks.
Then Schmidt turns to her favorite: Jupiter’s moon Europa. Slightly smaller than Earth’s moon, Europa might not seem like an ideal nursery at first. The surface temperature rarely exceeds –260 degrees Fahrenheit, and it is entirely covered by an ice shell up to 10 miles thick. Still, Schmidt says Europa is the only location in the solar system that clearly meets all three of life’s requirements. Although located a half-billion miles away from the sun, it receives a strong tug from the gravity of mighty Jupiter that warms the moon’s insides. Europa’s landscape is littered with molecules like sulfur dioxide and peroxide that are required for life. And best of all, beneath the ice shell resides an ocean of liquid water some 50 miles deep.
Astronomers have known about Europa’s biological trifecta for almost two decades, yet there have always been doubts: For Europa to support life, the vital molecules on the surface need to mix with the water and energy below, and there is a giant slab of ice lying in between. Late last year in a paper in Nature, Schmidt and University of Texas at Austin geophysicist Don Blankenship solved that problem. They demonstrated that the icy shell is most likely not a rigid barrier but rather a churning conveyor belt capable of shuttling life-friendly molecules from the frigid surface to the more inviting conditions far beneath.
Schmidt’s work suggests that water within Europa’s ice shell, and perhaps in the buried ocean, could be teeming with microbes—a development that has vaulted the intriguing moon into position as the next stop in the search for extraterrestrial life.
Making sense of chaos
Galileo Galilei discovered Europa using his homemade telescope in 1610, but it was not until 1972 that astronomers recognized the moon’s potential for life. That year MIT graduate student Carl Pilcher pointed the McMath Solar Telescope at Europa. Fitted with a spectrometer that measured the varying wavelengths of light reflected back to Earth, the scope allowed him to determine Europa’s composition, and prove that its surface is an expanse of frozen water.
As soon as they learned that there was water on Europa, scientists began exploring whether any of it could exist in liquid form. They got encouraging news a few years later, when researchers created the first detailed computer models of how the swirling dust and gravel present in the early solar system coalesced to form the planets and moons we see today. Based on Europa’s size and distance from the sun, the models indicated that it should have a metallic core, a rocky crust surrounding that, and a 60-mile layer of salty frozen water enveloping them both. But Europa’s position next to the solar system’s largest planet introduced an exciting x factor. Many physicists predicted that the gravitational bear hug Jupiter exerted on Europa as the moon drifted closer to the planet in its elliptical orbit, and the subsequent release as it drifted away, would generate friction and heat—enough heat, scientists guessed, to keep the bottom 50 or so miles of that salty water completely melted.
Astronomers had to wait two decades to test these predictions, but when NASA’s Galileo spacecraft settled into orbit around Jupiter in 1995, Europa did not disappoint. Galileo confirmed the existence of Europa’s buried liquid ocean. In addition, the probe’s spectrometer gathered far more detail than Pilcher’s Earth-based tool, revealing a surface abounding with sulfur, sulfur dioxide, and other biological necessities. The Galileo mission had proved that Europa satisfied the three conditions for supporting life. But the finding again came with a major asterisk: Europa’s thick shell of ice. There was still no clear evidence that the chemical ingredients above would be able to reach the nurturing environment below.
If scientists hoped to find a clear-cut path through which molecules might travel from the surface to the depths, the images Galileo sent back to Earth did not reveal it at all. Instead, they depicted a perplexing landscape like nowhere else in the solar system. The team, which included a young planetary scientist from Brown University named Robert Pappalardo, observed ridges and enormous fractures crisscrossing Europa’s surface, dividing it into slabs the size of small cities. Some sections appeared as smooth as a freshly resurfaced hockey rink; others looked as if they had been hacked up by a massive cosmic ax. A handful of high-resolution shots revealed areas with boulder-size chunks of ice and soaring elliptical domes that towered a few hundred yards above their surroundings. These regions were so confounding that Pappalardo and his team called them “chaos terrains.”
Europa’s chaotic surface was a mixed blessing for researchers seeking life. The ice shell was not just a flat, static slab prohibiting interaction between the realms. Yet scientists lacked any model that might explain the formation of those cracks and domes, or any solid ideas about a potential chemical exchange between surface and ocean that could sustain life. If they could make sense of the chaos, they could unravel the mechanism by which life might be cooked up.
The road to Europa
Around the same time that Galileo’s photos were tantalizing Pappalardo, 13-year-old Britney Schmidt was stargazing in a field near her home in Arizona. She remembers seeing the four largest moons of Jupiter, including Europa, through her school astronomy club’s 10-inch telescope and concluding passionately (if not entirely scientifically) that they were thoroughly awesome. Also a voracious reader, she breezed through a book about the Big Bang, showed it to her religious-education teacher, and said, “See, doesn’t this make more sense?”
A devotee of heavy metal rock, Schmidt lived for that bluntness and truth-seeking. She began her search in the world of literature, enrolling at the University of Arizona in 2000 as an English major. But by her sophomore year, she was banging her head against the wall with boredom. As class registration came up for the spring semester, she entertained the idea of transferring to music school in Chicago and learning enough to cover bands for magazines like Rolling Stone and Spin. Yet she decided to give Arizona one last chance by signing up for classes in a wide range of disciplines, hoping one would grab her.
One of those blind dart tosses hit a bull’s-eye: a class about life in the universe taught by planetary scientist Robert Brown. From the first day, Brown’s explanations of the prospects for life on Titan, Mars, and worlds in other solar systems struck an almost spiritual note with Schmidt. “I want us to think bigger and beyond ourselves and understand our place in the universe,” she says.
A few weeks into the semester, Brown described a seemingly mythical place called Europa, a frozen wasteland that nonetheless concealed a vast ocean potentially filled with life. “I was mind-boggled that this place existed and I’d never heard all of this,” Schmidt says. As in her religion class years earlier, she was not content to merely listen and accept. She started pestering Brown with questions about Europa’s ocean, its ice shell, and the molecules on its surface. Brown was so impressed with Schmidt’s curiosity and independent streak that late in the semester he sat her down in his office and told her she was wasting her time if she didn’t pursue planetary science. “She is a very self-motivated individual,” Brown says. “She’s a force.”
Chunks of ice would sink down toward the ocean, potentially bringing the ingredients of life along with them.
Schmidt didn’t need time to think. She switched her major to physics and volunteered for a research project analyzing Galileo images of Europan chunks of ice. By the time Schmidt finished college in 2005, she knew that she wanted to tackle the mystery of Europa’s chaotic ice shell. She was convinced that if there was life elsewhere in our solar system, it was going to be under that shell, and she wanted to figure out how it worked.
Unfortunately, Schmidt’s timing was terrible. That same year, NASA cut funding for a proposed multibillion-dollar mission called the Jupiter Icy Moons Observer, virtually eliminating all graduate-level jobs for studying Europa. She had to settle for an offer from ucla to study another icy object, a less glamorous asteroid called Pallas.
But Schmidt’s mind never strayed far from Europa, and in early 2007 she finally found an opening to pursue her passion. A colleague told her that NASA’s Jet Propulsion Laboratory in nearby Pasadena was hosting a series of meetings to begin planning a flagship mission to explore Europa. These meetings were limited to a select group of experts led by Pappalardo (who had become a prominent Europa scientist at JPL), but that wasn’t going to stop Schmidt. The idea that the future of Europa science was being determined just a short drive away was too exciting—and she was never shy about asking questions.
Schmidt emailed Pappalardo and asked if she could attend. “I basically said: ‘What can I do to get in the room? Do you need someone to make coffee? Would you like your shoes shined? Can I take notes?’ ” At first Pappalardo wasn’t sure how to respond. He had never heard a scientist, even a graduate student, volunteer for menial work. The group had plenty of coffee, and astronomers generally favor hiking boots over polished footwear. But the notes, he decided, would be useful.
Soon Schmidt was regularly jumping behind the wheel of her trusty car, Zorro, cranking up Metallica, and making the 45-minute drive to Pasadena. As she typed away in a corner of the room, she listened to the scientists try to make sense of Europa’s mysterious surface. The leading model came from Pappalardo. He proposed that the bottom layers of Europa’s ice shell would be slightly warmer than the ice on top, due to heating from both the ocean below and the crushing pressure of the miles-thick ice above. Heat rises, and so would this ice. He suggested that blobs of warmer ice would gradually float up and break through the shell, creating the soaring domes on the surface. Likewise, colder chunks of ice from above would sink down toward the ocean, potentially bringing the ingredients of life along with them. The model was persuasive, but there were still a lot of strange features on Europa’s surface, like fractures and icebergs, that Pappalardo’s model could not fully explain.
Other committee discussions focused on which instruments a spacecraft would need to study Europa’s ice. For that topic the scientists deferred to Don Blankenship, a University of Texas geophysicist and glaciologist with decades of experience using powerful radar to analyze ice sheets and glaciers in Antarctica. Schmidt was drawn to Blankenship immediately because he was the outsider, an ice guy in a room full of planetary-science wonks. She could also tell that although Blankenship was the so-called radar expert, he was really there for knowledge. He wanted to understand ice and to know whether Europa was another Antarctica. “There’s something to be said for a guy who’s just in the room because he wants to know,” she says. “That’s Don.”
Schmidt kept her hand down at the meetings, knowing her role. The informal discussion sessions that followed at nearby hotel bars were another matter. Over numerous nights and many beers, she pinged Blankenship with questions. She wanted to know about his trips to Antarctica, and whether a probe with powerful radar could actually reveal Europa’s secrets. But most of all, she wanted to know whether Pappalardo’s model of Europa’s ice sheet jibed with all he had learned from almost 30 years of studying ice on Earth.
Blankenship told her that although he agreed on the basics of Pappalardo’s model, he did not think that the warm blobs of ice would make it all the way to Europa’s surface. Instead, based on what he had seen in ice shelves on Earth, he guessed the warm plumes would melt the ice above them, creating pockets of liquid water embedded within the shell. From there, he hypothesized, water under enormous pressure from the ice above would flow in strange ways—horizontally or even uphill, seemingly defying gravity. These were difficult concepts to grasp, but Schmidt realized that they were essential for understanding an ice world like Europa.
After many nights talking with Blankenship, Schmidt was convinced that Pappalardo and his crew were disregarding an important source of knowledge in their attempt to solve the chaos puzzle: glaciology. If she wanted to figure out whether there could be life on Europa, she would have to turn herself into an expert on the ice here on Earth. So, as she put the finishing touches on her thesis in late 2009, she wrote to Blankenship and asked for a job in his lab. “A lot of people thought I was crazy for applying to an earth-science group after doing my Ph.D. on an asteroid,” she says. For Blankenship’s part, he typically limited his hires to geophysicists and electrical engineers for his missions to Antarctica; Europa was more of a personal side project. But Schmidt’s proposal to tackle the ice shell mystery was too enticing to pass up. In January 2010 Blankenship offered her a position. “We decided to get to work,” he says.
Messages in the Ice
When Schmidt moved to Austin in July 2010, the university installed her in an office a few doors down from Blankenship. She devoured papers on glaciology, memorized equations that dictated how deeply buried water and ice flow under pressure, and peppered Blankenship’s team with questions about how ice works on our own planet. “My plan was to use examples on Earth to explain the things we see on Europa,” she says.
Three months later, Schmidt joined Blankenship’s team on a research mission to the 600-square-mile McMurdo Ice Shelf in Antarctica. Now she was finally seeing the phenomena she had been learning about. Flying over the ice in a repurposed DC-3 military airplane, seeing the massive icebergs and the miles-long fractures splitting the surface like frozen lightning bolts, she could not stop thinking about the chaotic terrain hundreds of millions of miles away on Europa. “For somebody obsessed with ice, being in a place covered with ice was amazing. It felt like being on Europa,” she says.
As her Antarctic adventure drew to an end, Schmidt felt an encroaching sense of depression. It did not help that on December 14, less than two weeks after she returned to Austin, she was scheduled to outline her research at the American Geophysical Union (AGU) conference in San Francisco. “I was terrified,” she says. Yet something strange happened her first day back on campus. That combination of depression and terror—not to mention the extreme jet lag from 24 hours of flying—produced a mental state that she now refers to as her McMurdo high. “It was literally like time slowed down,” she says. “Every hour felt like a day. I’ve never been so productive.”
Closed off in her small office, Schmidt turned up her fail-safe Metallica to help her focus and started contemplating warm plumes of ice rising through Europa’s ice shell. Blankenship thought the warm ice would melt some of the ice above it as it ascended, leaving pockets of liquid water within the shell. Schmidt’s challenge was figuring out what that water would do next.
Solving the Puzzle
The simple assumption was that any pockets of warm, liquid water would drain downward through the ice and refreeze, but Schmidt had read enough studies to know that would not happen on Europa—the ice below was so thick it was virtually impermeable. By contrast, the ice above the water would become relatively unstable, its foundation melted away by the encroaching water. Following that logic, Schmidt concluded that the lid of ice above each water pocket would eventually cave in, crashing onto the liquid below. Through some calculations, she found that large volumes of water could remain trapped for thousands of years or more, enclosed on all sides by thick, insulating slabs of ice.
Schmidt knew her insight had major implications for life. She was suggesting that Europa’s ocean was not its only source of liquid water; the moon also harbored hidden lakes far closer to vital molecules on the surface, perhaps close enough to support miniature habitable ecosystems. But if she was going to persuade her instinctively skeptical colleagues, she would have to prove that this sort of process could actually happen. She needed to follow through with her strategy of supporting hypotheses about Europa by studying parallel features on Earth.
Schmidt rushed down the hall, past the three-foot-tall multicolored Galileo photomontage of Europa’s fractured surface taped to a column, and burst into Blankenship’s office. She summarized what she had deduced and asked if something like this could be taking place on Earth. He glanced over his glasses and replied, “Grimsvotn.”
In Iceland, the Grimsvotn volcano, buried miles beneath the ice sheet, melts the ice cap above it in the same way that the rising plumes might melt Europa’s shell, causing the surface of the Icelandic ice sheet to cave in. Back at her cluttered desk, Schmidt googled Grimsvotn and uncovered a few papers on the subject. Photos revealed a collapsed, fractured surface eerily similar to some of the chaotic regions of Europa. “I was practically hyperventilating,” she says.
The end of her two-week window came, and although she still had a lot of work to do, Schmidt and Blankenship quickly discussed her model and flew to the agu conference in San Francisco, where she presented it before a crowd of about 100 scientists. Her talk was well received, though some attendees pointed out that her model, like Pappalardo’s, was incomplete. There were still a lot of chaos features to explain.
That was fair criticism, but Schmidt was not done analyzing her Europan lakes, which she felt might explain all the moon’s chaotic topography. A few days later, back at her office whiteboard, she thought about the collapsed sheet of ice above each lake, full of giant fractures like the ones above Grimsvotn. She realized that if any of the fractures stretched deep enough into the ice, the water in the lake would suddenly have somewhere to go. Forced into the fractures of the caved-in ice, it would flow up, toward the surface.
The more Schmidt followed the water, the more compelling her model became. Over the course of weeks, years, or even millennia, she surmised, the tendrils of water leaking upward would refreeze. As they froze, they would also expand, just as ice cubes expand in the freezer. That would wreak havoc on the surrounding ice. Water freezing within the fractures would force the ice sheet apart, causing giant icebergs to break off.
Next, the icebergs would crush the smooth ice around them, creating regions of crunched, mutilated ice. Those regions, full of small cracks and crevices, would draw up even more water from below, which would then freeze and swell into soaring, solid domes of ice—the final piece of the Europa puzzle. By simply tracking water as it melted, migrated, and refroze, Schmidt had, in mere months following a trip to the Antarctic, come up with by far the most complete model of the icy moon’s chaotic surface.
After months of fine-tuning, Schmidt and Blankenship published their model in Nature last November. Pappalardo was skeptical until Schmidt presented it before him and other Europa experts at jpl. “All the pieces just started fitting together,” he now says.
Hunting Aliens
An immediate rush of media attention focused on Europa’s lakes. Schmidt had shown that they could subsist just a mile or two beneath the Europan surface, shallow enough that scientists could plausibly imagine drilling through the ice and accessing them. These lakes could also be hotbeds for life, since molecules embedded in surface ice could easily get dumped into the water when the ice collapses. Schmidt’s paper specifically singled out a chaos region on Europa called Thera Macula, which could conceal a lake containing as much water as all the Great Lakes combined.
To Schmidt, though, the lakes alone are not the big discovery. Her real breakthrough is finding the mechanism by which molecules on Europa’s surface could unite with water and energy in the lakes, and maybe even in the vast, deeper ocean. “You’ve got all this warm water moving up,” she says, “but at the same time all the heavy, cold ice stocked with chemicals is getting pushed down toward the ocean.” Her model describes the ice sheet as a heat-driven conveyor belt enabling the three requirements of life—water, energy, and chemistry—to exist in the same place at the same time. “We’re basically implying the ice is like a washing machine, mixing all those ingredients together,” Schmidt says. “It gets me and a lot of other people really excited.”
With Schmidt’s work reenergizing the field, Pappalardo and his team have sketched out new proposals for missions to Europa. One option calls for a spacecraft that would map the surface in detail and measure the depth and salinity of the buried ocean. Another would loop around Jupiter and complete more than 30 Europa flybys, employing ice-penetrating radar to probe the icy shell.
At about $2 billion each, the missions are pricey, especially given NASA’s recent preference for multiple small missions rather than one or two big-budget ones. But Pappalardo believes that the compelling science, combined with the recent success of NASA’s similarly expensive Mars rover, Curiosity, may convince the agency to alter its strategy. Getting a real answer about life on Europa will require landing and drilling—something well beyond current budgets and technology. At the very least, Europa will get a visit from the European Space Agency. In May it approved the Jupiter Icy Moons Explorer, a probe slated for launch in 2022 that will measure the thickness of Europa’s ice shell.
In the meantime, Schmidt and other Europa experts are doing all they can to prepare for a return to Europa by studying parallel environments here on Earth. To see how an alien habitat could develop inside that active, churning ice shell, Schmidt and Blankenship plan to send robotic vehicles down into small lakes beneath the McMurdo shelf beginning this month.
Schmidt says that there is reason to believe those cold, pressurized puddles can support a diverse collection of organisms. For her, the prospect of finding extraterrestrial life is everything. That is why she has been working nonstop, obsessing over Europa, cramming several years’ worth of work into one. “I have been going really fast, but the reason is that I want to know in my damn lifetime,” she says. “It would be really, really nice if someone discovered something wiggling around.”
Europa on Earth
It may be years before scientists can explore directly beneath the ice on Europa, but in the meantime they can explore Lake Vostok, a vast body of water hidden beneath the thick glaciers of Antarctica. In February—just three months after Britney Schmidt proposed the possibility of subglacial lakes within Europa’s thick ice crust—Russian scientists announced that they had drilled through the ice to reach Vostok. Like the inferred lakes on Europa, Vostok lies some two miles under a shell of surface ice and remains liquid due to the crushing pressure of that overlying mass. Schmidt’s colleague Don Blankenship says he will be paying close attention to how Vostok’s water flows under such pressure because that will reveal how easily the ingredients of life could interact within Europan lakes. Other scientists are interested in the frigid surface above Vostok, which should serve as an ideal test site for autonomous robots designed to drill on Europa and search for hidden life.—G. M.
Gregory Mone is a frequent DISCOVER contributor and author of The Truth About Santa: Wormholes, Robots, and What Really Happens on Christmas Eve.
