A rough look at the logistics of finding life on Enceladus
For all the beautiful images of Saturn captured by the Cassini spacecraft since it started it’s mission in 2008, the hot spot scientists want to see a lot more of is actually the moon Enceladus. Reoccurring geysers of briny water have been blasting out of the moon’s surface, indicating that it may have a thick layer of liquid water below its icy exterior. As unenticing as this kind of environment would be for us, it may be hospitable enough to be home to some basic forms of life. This tantalizing prospect has scientists from various disciplines working together to figure out the logistics of how we could find traces of potential life the next time we’re in Saturn’s neighborhood.
Samples shot into space
One of the obvious issues is how to come in contact with waterborne life living under six miles of ice. Landing spacecraft isn’t easy, but fortunately it may not be necessary. The same geysers that tipped us off to the presence of liquid water may also act as a delivery system, sending microbes deep enough into space for a future probe to fly by and scoop up a sample for analysis. The geysers seem to operate on a bit of a schedule, and so our probe would just have to be at the right place at the right time. Then again, we’d also need the microbes to be there too.
This is where oceanic experts enter the discussion, pointing out that even though our oceans hold massive amounts of living organisms, they’re not distributed equally around the world. As such, there’s a chance that the microbes might be in the wrong place, or just at the wrong depth, to be blasted out of Enceladus’ cold waters on a regular basis. Our best hope may then be that Enceladus is home to a phenomenon called “bubble scrubbing,” where bubbles of gas moving up through a water column manage to pick up small bits of the solid matter they bump into on their journey to the surface. The bubbles basically act like a drag net, carrying dust or microbes up from their deeper homes, and hopefully all the way into space.
How to know it when you see it
Assuming the microbes could be delivered to our theoretical spacecraft, there would still be an array of problems to solve. How to do you catch a bucketful of tiny organisms at orbital speeds without smashing them in the process? Once you have them contained, how do you study and document them? Is it possible to photograph single cells with any detail? And of course the big question, if you have a batch of watery debris, what constitutes signs of life in the first place?
While it would be great to find something as obvious as a cell, we’re likely to have to settle for dead tissue, or maybe just biological byproducts. The two substances to really look out for would be lipids, proteins most commonly used in cell membranes, and amino acids, the compounds that are used to assemble every biological agent we know of. Amino acids aren’t a perfect piece of evidence, since we’ve found them on comets without living organisms, but they’d still raise the possibility that these key organic molecules were delivered across our solar system, taking root on Earth and possibly elsewhere. Alternatively, if life is found that doesn’t make use of lipids or known amino acids, it would mean that living tissue isn’t bound by the rules we know of, and may be much more widespread throughout the universe. Either option is pretty exciting, assuming something can be found in the first place.
Source: Excitement Builds for the Possibility of Life on Enceladus by Annie Sneed, Scientific American
