Will Enceladus finally answer “Are we alone?”

We recently looked at how and why the planet Mars could answer the long-standing question: Are we alone? There is evidence to suggest that it was once a much warmer and wetter world thanks to countless spacecraft, landers and rovers that have 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 cracks near its south pole, strong evidence for an internal ocean and possibly life. Here, we will examine 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 explored the Saturn system, eventually multiple flybys starting at this icy moon20 It was these flybys that revealed the unique geology and composition of Enceladus.

“Enceladus has many of the ingredients we think are necessary for life: an ocean of liquid water beneath an icy shell. an energy source (tidal heating). and nutrients (we have detected carbon compounds, which could be used as food),” said Dr. Francis Nimmo, who is a Professor in the Department of Earth and Planetary Sciences at the University of California, Santa Cruz. “In that respect it is not so different from other moons with subsurface oceans, such as 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 space, where we can collect them with a passing spacecraft and analyze them. So Enceladus is a very good place to go and look for possible life because we can *directly* sample material from the ocean.”

NASA’s Cassini spacecraft used its mass spectrometer to detect organic materials, water vapor, carbon dioxide, carbon monoxide and a mixture of volatile gases inside these geysers. could they show the presence of life. Not only do active geysers indicate the presence of an internal ocean, but it is also indicative of an energy source on Enceladus.

“Enceladus has captivated the astrobiological community because it is the first icy ocean world for which we have strong evidence to support its habitability,” said Dr. Christopher Glein, who is chief scientist and geochemist at the Southwest Research Institute in Texas. “Data from the Cassini mission shows that Enceladus has the three ingredients required for life as we know it. These are liquid water, essential elements (including organic molecules) and a source of energy that can be harnessed by life. Recently, we discovered that the geochemistry of Enceladus’ ocean makes phosphate minerals unusually soluble there. This strongly suggests that the availability of phosphorus will not hinder the prospects for life, but 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, there are several future missions under study that could help us further understand Enceladus and whether it can support life. This includes NASA’s Enceladus Orbilander, whose science goals include determining if Enceladus has life, how it has life, and identifying a suitable landing site for a potential mission to the surface.

“The Orbilander is designed to answer the question of whether there is life in Enceladus’ ocean as clearly as possible,” Dr Nimmo said. “Because we don’t know what form life would take, Orbilander uses many different techniques to look for the presence of life-like properties. And because most of the material ejected from the geysers ends up back on the surface, the Orbilander will search the surface “snow” for signs of life, as well as material going into orbit around Enceladus. After the Orbilander, we should have a pretty good idea of ​​whether Enceladus is inhabited or not.”

While we wait for another spacecraft to revisit Enceladus, scientists continue to gather data from the Cassini mission to try to squeeze in every last bit of science about Saturn’s icy moon. We know it has an ocean, which points to the potential for life, but what kind of life could thrive in its oceanic depths? How has it evolved and is it similar to life on Earth?

“Enceladus is perhaps the most enigmatic ocean world. It’s so small it shouldn’t have an ocean, but it does. After more than a decade of study, we now have a better understanding of how strong tidal forces keep the interior warm and make Enceladus geologically alive. Could these same forces also maintain 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 it skimmed within 25 kilometers (15.6 miles) of the surface. (Credit: NASA/JPL/Space Science Institute)