Roughly the size of France, the Ross Ice Shelf is an inhospitable land, if you can even call it that. There, hanging from the edge of Antarctica, the ice sinks a half-mile thick. So thick, in fact, that until late January, no one thought life beyond microbes could exist beneath the ice in frigid waters of perpetual darkness. But then a team of scientists sank a probe down to the sea bottom, which they found to be “rocky, like a lunar surface.” The probe, unexpectedly, wasn’t alone.
Like a wraith, a translucent fish shimmered into view. No one could believe it. There were dozens of them — and an amphipod, too — swimming and surviving in waters that shouldn’t have been able to support life. Beneath more than 2,400 feet of ice and more than 500 miles from the shelf’s edge, there was life. And no one’s quite sure how.
These creatures are known as an extremophiles, a life form that survives in an extremely hostile environment. It also signals the irony of modern space exploration: The search for extraterrestrial life begins, strangely enough, here. If a fish – a fish! – can survive beneath all that ice, what does that mean for what may lurk beneath the ice of Jupiter’s moon Europa? What does that mean for Saturn’s moon Enceladus?
“Discoveries of extreme life here on Earth often provoke speculation about what might lurk in other worlds,” wrote Scientific American’s Douglas Fox. “… People asked what this might mean for finding life on distant worlds such as Europa, a moon of Jupiter that very likely harbors an ocean of liquid water beneath a crust of ice.”
Wednesday brought more exciting news in astrobiology. A paper published in Nature made the case that Enceladus could have what it takes to support life. In 2005, NASA’s Cassini spacecraft discovered evidence of geysers that might have emitted plumes of water. But now, according to the paper, scientists have found what NASA called “the first clear evidence” that those plumes could be linked to an active hydrothermal system in the moon “which may resemble that seen in the deep oceans on Earth.”
The news marked the latest in a drumbeat that has caused some scientists to conclude that an answer to the age-old question of whether we’re alone in the universe may be on the horizon. “My colleagues and I are optimistic that evidence for life, either elsewhere in our solar system or elsewhere in the universe, may be discovered in the coming decades,” Lawrence M. Krauss wrote in the New Yorker in late January.
There are several reasons for such optimism. Space exploration is expanding at a dizzying rate. Researchers keep discovering new extremophiles in hostile environments, widening the accepted conditions required for life to survive beyond our planet. Again, a fish. Beneath a half-mile of ice. Hundreds of lateral miles removed from sunlight.
“There are a host of possible sites where life might have evolved that were long considered unlikely,” Krauss wrote. “… On Earth, scientists have had to revise old rules about where and how life can survive. The discovery of so-called extremophiles … has vastly increased the set of conditions under which we can imagine life existing on this planet.”
Then there is the rapidly emerging number of exoplanets. The first was discovered in 1995, when Michel Mayor and Didier Queloz of the University of Geneva spotted 51 Pegasi, dozens of light years away. “After that, the floodgates opened,” wrote Michael D. Lemonick in National Geographic. Researchers have since found nearly 2,000 of these planets. And some of them seem ripe for life.
One in particular was discovered in June last year, only a dozen light years away, parked smack in the “Goldilocks” zone. This zone specifies the requisite distance from a sun a planet must be for there to be liquid water, considered vital by scientists for the existence of life. Thus, not too hot, not too cold: Goldilocks. Then this year, astronomers announced the discovery of eight additional Goldilocks planets.
And that’s only the start. In the coming years, a slew of what may be revolutionary telescopes will swivel skyward. There’s the appropriately named European Extremely Large Telescope. There’s the NASA-approved Transiting Exoplanet Survey Satellite, which should start hunting for planets in 2017. And the James Webb Space Telescope is scheduled for a 2018 start.
The search for extraterrestrials long ago transitioned from the realm of science fiction to scientific pursuit. At first blush, it seemed a hopeless one. Life on Earth seemed a product of hundreds of factors that miraculously went our way. Take Jupiter. If it hadn’t existed, exerting its massive gravity on the solar system, comets would have pulverized Earth, throwing a wrench into the wheels of creation. Take the moon. If it hadn’t been around, the Earth wouldn’t have its seasons or tides. Plus, we’re squarely in the Goldilocks zone.
“By considering each of these many factors and imagining the probability of each separately, one can imagine that the combination is statistically very unlikely, or impossible,” Krauss wrote of Earth’s chances. But that’s not so, he said. Rather, recent research and the discovery of these extremophiles indicate how life can sprout in ways scientists never imagined.
“On Earth, these are niche environments,” Lisa Kaltenegger, of Harvard University and Germany’s Max Planck Institute for Astronomy, told National Geographic. “But on another planet, you can easily envision that they could be the dominant scenarios.”