We recently looked at how and why the planet Mars could answer the long-standing question: Are we alone? There is evidence to suggest it was once a much warmer and wetter world thanks to countless spacecraft, landers and rovers having explored – and are currently exploring – its atmosphere, surface and interior. Here we’ll look at another of Saturn’s 83 moons, an icy world that spews geysers of water ice from giant fissures near its south pole, which is strong evidence of an inner ocean and possibly of life. Here we are going to look at Enceladus.
In terms of space exploration, Enceladus was briefly visited by NASA’s Voyager 1 and Voyager 2 in 1980 and 1981, respectively, and was not visited again until NASA’s Cassini spacecraft had explored the Saturn system, eventually performing several flybys of this icy moon beginning in 2005. It was these flybys that revealed Enceladus’ unique geology and composition.
“Enceladus has many of the ingredients we think are necessary for life: an ocean of liquid water under a shell of ice; a source of energy (tidal heating); and nutrients (we have detected carbon compounds, which could be used as food),” said Dr. Francis Nimmo, a professor in the Department of Earth and Planetary Sciences at the University of California, Santa Cruz. with subterranean oceans, like Europa. What makes Enceladus unique is that it gives us free samples of its ocean: there are geysers that shoot water vapor and ice crystals into the space, where we can pick them up with a passing spacecraft and analyze them, so Enceladus is a really good place to go for potential life, because we can *directly* sample material from the ocean.
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NASA’s Cassini spacecraft used its mass spectrometer to discover organic materials, water vapor, carbon dioxide, carbon monoxide and a mixture of volatile gases in these geysers, which could indicate the presence of life. Not only do the active geysers indicate the presence of an internal ocean, they also indicate a power source within Enceladus.
“Enceladus has captivated the astrobiology community because it is the first icy ocean world for which we have strong evidence to support its habitability,” said lead scientist and geochemist Dr. Southwest Research Institute in Texas. “Data from the Cassini mission shows that Enceladus has the three ingredients necessary for life as we know it. They are liquid water, essential elements (including organic molecules) and a source of exploitable energy. Recently, we discovered that the geochemistry of the ocean of Enceladus makes phosphate minerals exceptionally soluble.This strongly suggests that the availability of phosphorus will not hinder the prospects for life but rather should serve as an opportunity.
With the Cassini mission ending in 2017, there are currently no active missions exploring the Saturn system, let alone Enceladus. However, several future missions are currently being investigated that could help us better understand Enceladus and whether it can support life. This includes NASA’s Enceladus Orbilander, whose science goals include determining whether Enceladus has life, how it has life, and also locating a suitable landing site for a potential surface mission.
“Orbilander is designed to answer the question of whether there is life in the ocean of Enceladus as clearly as possible,” said Dr Nimmo. “Because we don’t know what form life would take, Orbilander uses several different techniques to search for the presence of life-like attributes. And because most material that comes out of geysers ends up on the surface, Orbilander will search “snow” on the surface of signs of life, as well as in materials orbiting Enceladus After Orbilander, we should have a pretty good idea of whether Enceladus is inhabited or not.
While we wait for another spacecraft to re-visit Enceladus, scientists continue to dump data from the Cassini mission to try to get the most out of science on Saturn’s icy moon. We know there is an ocean, which indicates the possibility of life, but what kinds of life could thrive in its ocean depths? How did it evolve and does it resemble life on Earth?
“Enceladus is perhaps the most confusing of the ocean worlds. It’s so small it shouldn’t be an ocean, yet it is. After more than a decade of study, we now have a better understanding of how powerful tidal forces keep the interior warm and make Enceladus geologically alive Could these same forces also support biological activity?
And with that, we wonder if Enceladus will finally answer, “Are we alone?
As always, keep doing science and keep looking up!
Featured image: Saturn’s moon Enceladus, taken by NASA’s Cassini spacecraft on October 9, 2008, after skimming the surface less than 25 kilometers (15.6 miles) away. (Credit: NASA/JPL/Institute of Space Sciences)
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