Unmasking Enceladus

We are on the cutting edge of one of the most important discoveries in human history: the first evidence of extraterrestrial life on Saturn’s moon Enceladus. We, humans, are trying to find a habitable planet in other galaxies, far away – Trappist-1 system, when there is a habitable planet(moon) right next door.

Planetary bodies with oceans are prime targets in the search for life beyond Earth owing to the essential role of liquid water in biochemical reactions that sustain living organisms. In addition to water, life requires energy and a source of essential chemical elements (C, H, N, O, P, and S). So one can say ‘Water is the elixir of life.’

NASA’s Cassini spacecraft has picked up the first evidence that chemical reactions are happening deep below the ice which could be creating an environment capable of supporting microbes. The same sorts of chemical reactions that sustain life near deep-sea hydrothermal vents here on Earth could potentially be occurring within Enceladus’ subsurface ocean, a new study published a few days back (April 13, 2017) in the journal Science suggests.

Enceladus as viewed from NASA’s Cassini spacecraft.

The 313-mile-wide (504 kilometers) Enceladus is just Saturn’s sixth-largest moon, but the object has loomed large in the minds of astrobiologists since 2005.

In that year, NASA’s Saturn-orbiting Cassini spacecraft first spotted geysers of water ice erupting from “tiger stripe” fissures near Enceladus’ south pole. Scientists think these geysers are blasting material from a sizeable ocean buried beneath the satellite’s ice shell.

Cassini Spacecraft

So, Enceladus has liquid water, one of the key ingredients required for life as we know it. (This ocean stays liquid because Saturn’s immense gravitational pull twists and stretches the moon, generating internal “tidal” heat.) And the new study suggests that the satellite possesses another key ingredient as well: an energy source.

Plumes of substances/vapour spray out from the surface of Enceladuds’ ocean – one of the substance is hydrogen.

Hydrogen gas, which could potentially provide a chemical energy source for life, is pouring into the subsurface ocean of Enceladus from hydrothermal activity on the seafloor. The presence of ample hydrogen in the moon’s ocean means that microbes – if any exist there – could use it to obtain energy by combining the hydrogen with carbon dioxide dissolved in the water.

The molecular hydrogen is most likely being produced continuously by reactions between hot water and rock in and around Enceladus’ core. The hydrothermal explanation is also consistent with a 2016 study by another research group, which concluded that tiny silica grains detected by Cassini could have been produced only in hot water at significant depths.

Plumes of vapour shooting up from Enceladus’ ocean.

 Earth’s deep-sea hydrothermal vents support rich communities of life, ecosystems powered by chemical energy rather than sunlight. Some of the most primitive metabolic pathways utilized by microbes in these environments involve the reduction of carbon dioxide (CO2) with H2 to form methane (CH4) by a process known as methanogenesis, The inferred presence of H2 and CO2 in Enceladus’ ocean therefore suggests that similar reactions could well be occurring deep beneath the moon’s icy shell. Indeed, the observed H2 levels indicate that a lot of chemical energy is potentially available in the ocean.

So if life can grow in similar conditions on earth then why not on this natural satellite.

The presence of H2 in the Enceladus’ ocean is an indicator for the presence of life.

So the final question is “Are We Alone?”