NASA Scientists Discover Places that Could Harbor Life in Our Solar System

NASA Scientists Discover Places that Could Harbor Life in Our Solar System
June 30, 2017

The search for extra-terrestrial life may keep astronomers far closer to home than previously thought, as two NASA missions have uncovered some of the most compelling evidence for life within our solar system to date.

Hydrothermal Vents and Plumes on EnceladusTwo icy moons, one orbiting Jupiter and the other orbiting Saturn, recently displayed evidence of warm spots capable of supporting liquid water and chemical reactions that can provide both food and a hospitable environment for life.

"This is the closest we've come, so far, to identifying a place with some of the ingredients needed for a habitable environment," said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate Thomas Zurbuchen in a press release. "These results demonstrate the interconnected nature of NASA's science missions that are getting us closer to answering whether we are indeed alone or not."

Both moons, Europa and Enceladus, are too cold and far away from the sun to allow for liquid water at their surfaces. Much like Earth, however, the interior of the planet is hot, so underneath that crust of ice are oceans of liquid water.

Astonomers hypothesized that at the floor of these oceans are hydrothermal vents, like ones on Earth that blast out superheated, mineral-rich water. On Earth, these places harbor some of the most ancient life forms known to man. They harvest the chemical energy from hydrogen molecules made in the vents, and spit out methane, so scientists believe that if life were to exist on the moons, it would need hydrogen, warm water and a carbon source like carbon dioxide.

Cassini ProbeNASA scientists found all three of those ingredients on Enceladus, a small moon orbiting Saturn.  The hydrothermal vents on icy moons can sometimes propel enough hot water toward the surface, that it punches a hole in the ice and sprays water and anything dissolved in it into space. NASA’s Cassini probe, a small satellite launched two decades ago to study Saturn and its moons, flew through one of these spray fields, which astronomers call plumes, near the South Pole of Enceladus and scooped up the icy mist.

Cassini’s onboard chemical analysis hardware revealed that the spray was roughly 98 percent water and 1 percent hydrogen, with carbon dioxide, methane, ammonia and other small molecules making up the remainder. Previous research concluded that hydrothermal vents could be doing some of the chemistry and heating required to support life on these moons, but finding hydrogen in the vapor plume greatly strengthens the theory that life is possible deep in the oceans of Enceladus. Cassini does not have the tools to detect life directly, but Hunter Waite, the lead author of the Science paper discussing the Cassini find, described the hydrogen as a “candy store” for microbial life.

Plumes are not unique to Enceladus, either, as astronomers with the Hubble Space Telescope mission recently observed what looked like a plume rising more than 60 miles from the surface of Europa, one of Jupiter’s moons. Hubble detected something that looked like a plume in the exact same spot on Europa in 2014, and when the scientists looked at it with thermal imaging, they found a hot spot right at the source of the possible plume. 

Interior of EuropaThe hot spot bolsters the theory that hydrothermal vents are causing the plumes, and if that theory is correct, it is possible that microbial life could be living on Europa as well. 

The Cassini probe is not equipped to search for life, and even if it were, it is scheduled to have its “Grand Finale,” a one-way trip into the interior of Saturn, this fall. NASA scientists also do not want to risk an errant, hitchhiking microbe from Earth somehow making its way onto Enceladus from Cassini and causing an interplanetary invasive species problem.

All that said, an upcoming NASA mission called Europa Clipper will get a chance to study Europa’s possible plumes and oceans from a distance of just 16 miles above the moon’s surface (less than one fifteenth the orbital height of the International Space Station). The probe will launch sometime in the 2020s and will pass Europa 45 times, providing plenty of opportunity to search for possible signatures of life while characterizing the moon itself.

Finding life on these icy moons close to home would greatly open up the possibilities for Earth-like life in other solar systems. If life could appear in the deepest reaches of icy moons, then our galaxy could be positively bursting with small microbial life. If it has yet to evolve in places like Europa and Enceladus, where Earth-like life should show up, then the galaxy might be more sparsely populated, and Earth more unique than scientists previously thought.

Either way, these discoveries of habitable places could dramatically affect how we think about life beyond our own planet.

—Daniel Lane

Daniel Lane covers science, medicine, engineering and the environment in North Carolina.

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