Scientists Meet To Discuss Exploring Enceladus For Life
Ever since 2005, when the Cassini spacecraft discovered that Enceladus shoots geysers of liquid water 125 miles into space, the little icy moon orbiting Saturn has tantalized planetary scientists. Not only does the moon likely have a warm subsurface ocean thanks to the gravitational pull of Saturn, but it also periodically flings material from that ocean out where an orbiting spacecraft can sample it. Whether Enceladus is more likely to be habitable than other watery worlds such as Jupiter's moon Europa is a matter of pure speculation-but whether it would be easier to search for life on Enceladus than on other worlds is a clear yes.
This is the conclusion of planetary scientists like Carolyn Porco, head of the imaging team for the Cassini mission. Earlier this month, she organized a meeting at the University of California, Berkeley, with astrobiologists, organic chemists, and oceanographers to discuss the best way to search for life on Enceladus, according to Scientific American.
To search for life on Mars or Europa, we need to land a spacecraft on the celestial body and either search the surface or tunnel through layers of ice to get to the liquid ocean beneath. We are already searching Mars's surface for signs of life, and the new Mars 2020 rover will continue to probe the planet for all its secrets. There are also some intriguing ideas to tunnel through Europa's surface ice with a heat exchanger that would use high-pressure jets to carve a hole in the ice-technology that is being demonstrated in Alaska. But at Enceladus, maybe all we need to do is fly through the towering geysers with a spacecraft designed to identify signs of organic life.
At Enceladus, 888 million miles from the sun, any life would be encased in somewhere between 2 and 20 kilometers of ice. The leading theory is that organisms could cling to hydrothermal vents near the core of Enceladus, similar to the vast ecosystems on the ocean floor of Earth that manage to survive while completely cut off from the energy of the sun. If we assume life does in fact exist on Enceladus, the question is, will that life be detectable in the plumes that shoot out into space?
It may be that any life near the core of the small moon would leave no trace in the geysers erupting from the surface. However, at the meeting lead by Porco, the scientists discussed the possibility that a process known as "bubble scrubbing" could deposit organic material in Enceladus's geysers. At Earth's hydrothermal vents, bubbles rip organisms and organic material from the walls of water columns, mixing it in with waters closer to the surface of the ocean. A similar process on Saturn's little moon could mean the water erupting from the surface would have detectable traces of life.
We already have a spacecraft in the area, Cassini, and it already flew threw the geysers of Enceladus, but it doesn't have the necessary science instruments to conduct a thorough search for organic life. The data taken in that flyby is still being analyzed, with no conclusive evidence regarding habitability one way or another.
We need a new spacecraft, one specifically designed to probe Enceladus for life.
We need a new spacecraft, many argue, one specifically designed to probe Enceladus for life. It will be difficult to take a sample without crushing any organic molecules when the spacecraft soars through a water plume at high speeds, but many at the UC Berkeley meeting are optimistic that advanced science instruments could find molecules indicative of life, and maybe even life itself.
There is a remote possibility that a near-future spacecraft actually manages to take images of life eating or reproducing or swimming around. But confirming that images of microbial life actually depict living organisms and not just a collection of particles would prove difficult.
However, there are other, less direct ways of searching for life in a water sample. Amino acids, used by cells to create proteins, and lipids such as fats and waxes-used to build outer cellular walls-could point to life on Enceladus. These two types of molecules exist where life does not, such as on comets and meteorites, so scientists would be looking for unique structures and distributions of amino acids and lipids that are not thought to occur due to natural chemical processes-the specific arrangements are made by life. If scientists see these structures of amino acids and proteins, it would be convincing evidence that life exists.
There is also the possibility that extraterrestrial life is nothing like life on Earth.
There is also the possibility that extraterrestrial life is nothing like life on Earth-that it doesn't use the same types of molecules in the same ways. During the Berkeley meeting, Porco brought up the possibility that life on Enceladus doesn't even use amino acids. If that's the case, "then we're sunk and nature is perverse," said Chris McKay, a planetary scientist at NASA Ames Research Center, according to Scientific American. "We should all just give up and become poets."
That is the grim reality of sending a spacecraft to Enceladus to search for life in the water plumes-the most likely scenario is that nothing conclusive can be determined from the data. Confirming the existence of alien life in our solar system would almost certainly require evidence from a number of different science experiments and possibly multiple missions.
Still, scientists are confident that the environment at Enceladus could sustain life, and flying through the moon's watery plumes a few times would be much easier than tunneling through the surface ice. It's a high-risk mission because it would cost hundreds of millions, and it might come up empty. But from the prospective of a planetary scientist, the potential reward has never been higher.
Source: Scientific American
