School: Eyuboglu High School
Teacher: Burcu Parmak Yildirim
"This year there were three candidates for where the next spacecraft should be sent to: Titan, Europe and Enceladus. I chose to defend Enceladus, because I believe that it might have life in its subsurface ocean.
The spacecraft Cassini was able to sample the spray ejected from Enceladus and discover that it contained liquid water and organic molecules like methane, carbon dioxide, ammonia and hydrogen. These increases the possibility that it can have simple life forms in its ocean. We know that in extreme environments on Earth, hydrogen can act as an energy source to feed life. There is a type of archaea called methanogens, who are anaerobic organisms which are thought to be one of the oldest microorganisms on Earth. They use hydrogen and carbon dioxide as energy sources and produce methane. On Earth they can be found in extreme conditions like the submarine hydrothermal vents. Luckily, Enceladus likely has hydrothermal vents like Earth does.
Linda Spilker, a project scientist on the Cassini mission said “Enceladus is too small to have retained the hydrogen from when it formed, so the hydrogen we see today is coming from inside Enceladus.”And according to principal investigator Hunter Waite of the SWRI, the source of molecular hydrogen ejected from the geysers has to be hydrothermal vents at Enceladus’ sea floor. Other clues that point to the existence of hydrothermal vents are the grains of silica found in the E ring of Saturn, which Enceladus feeds and the excess amounts of methane found in the plume material.
Enceladus nearly reflects all the light that reaches it and has an average surface temperature of -201֯C. This might be too cold for life to exist. Its equator doesn’t hold much promise either, with having an average surface temperature -188 ֯C. Fortunately, Enceladus has this region on its South Pole which is informally called Tiger Stripes. These Tiger Stripes are where the geysers are located and is considerably warmer than the rest of the moon, having a temperature of -90 ֯C. This region might be a suitable habitat for organism like the methanogens.
Enceladus also has the necessary things needed for the deep sea vent theory (a theory that suggest life was first formed away from sunlight, near the geysers on the ocean bed): an ocean rich with minerals and salt, CO2 and H2.
I believe that the highly possible existence of the hydrothermal vents in the seafloor along with the organic molecules discovered makes Enceladus have great chances of harboring simple life forms. Because as Morgan Cable, NASA JPL said, “A lot of origin-of-life scientists believe that his is the place(hydrothermal vents) where life could have started on Earth.” Also, the geysers offer free samples which means landing a craft and drilling to surface to reach the ocean could become unnecessary. And this is why the next space craft must first be sent to Enceladus, so that we can find answers to the mysteries of Enceladus as soon as possible."