Year: 2018-19
Michael Cheng
School: University of Toronto Schools
City: Toronto (Province: Ontario)
Teacher: María I. Niño-Soto
The history of science is filled with counterintuitive results. The path of the stars and planets through the night sky seemed to suggest that the earth was at the centre of the universe. However, through careful analysis and observation, Copernicus produced the heliocentric model of the solar system, which is still widely accepted nearly 500 years after its proposal. Likewise, although the moons of Saturn seem like an unlikely home to living beings, Enceladus’ plumes, ice, and the chemical composition of its oceans make it both easy to study and an ideal starting ground for life.
The relative ease at which data can be collected makes Enceladus a researcher’s dream. Due to the gaseous plumes it emits, Enceladus’ chemical composition can be analyzed without landing. Cassini flybys in 2012 found water vapour plumes containing substances important to life such as ammonia, methane, nitrogen, hydrogen, salts, and organic compounds.
Additionally, shifts in radio signals caused by the Doppler Effect during said flybys confirmed suspicions of a global ocean covering Enceladus under that ice (NASA, 2018). The ability of water to facilitate biochemical reactions makes it an essential aspect of life, and the discovery of an ocean underneath the surface makes Enceladan life much more plausible.
Enceladus also contains all the properties and other chemical components needed for life. The presence of silica in Enceladan plumes, a substance that forms at temperatures greater than 90℃, suggests the presence of hydrothermal vents (NASA, 2018). Additionally, the ice at the surface of the moon acts as a thermal insulator, maintaining the necessary temperatures for biochemical reactions such synthesizing amino acids.
As shown by the famous Miller-Urey study, it is possible to synthesize amino acids such as glycine and aspartic acid in the presence of the ammonia, methane, water, and hydrogen found on Enceladus (Miller, 1953). This is congruent with a more modern study published in Nature by the Southwest Research Institute which found complex organic compounds with masses of over 200 amu in Enceladan plumes. Many of these compounds displayed structures such as amino and carboxyl groups that are also found in amino acids. These molecules are unique to Enceladus, with the plumes of Europa only showing organic compounds of up to 50 amu (Postberg, 2018). The presence of various salts in the oceans is also significant, as they allow cells to control the flow of water via passive and active transport (Kaiser, 2018). These conditions bear a striking resemblance to an early earth where the proposed first lifeform, the Last Universal Common Ancestor, or LUCA, emerged (Weiss, 2018). The chemical composition of Enceladan oceans provide the perfect “primordial soup” from which similar organisms can surface.
Enceladus’ plumes, ice, and chemical composition, make it an ideal place for sustaining life. Unique aspects such as the presence of compounds similar to amino acids make it an equally viable, if not superior place for astrobiologists to study compared to Titan and Europa. By sending another mission to Enceladus, humanity’s knowledge of astrobiology will be greatly improved, and the legacy of the Cassini-Huygens mission will continue into the future.
