The Search For Extraterrestrial Life In The Water Worlds Close To Home

The ConversationThe discovery of seven exoplanets around a star 40 many years from your Sun has elevated the chance that they might harbour life.

Why? Since the astronomers who made the invention believe a few of the planets might have liquid water. As well as on Earth, wherever there’s liquid water, there’s existence.

But we feel we are able to look much nearer to Earth for potential candidates for proof of extraterrestrial existence, once we condition this month within the International Journal of Astrobiology.

Recent breakthroughs through the NASA Voyager and Cassini space missions infer the existence of liquid oceans beneath a ocean ice crust on a few of the moons of Jupiter and Saturn.

These supply the probably sites for locating extraterrestial existence within our solar system.

Much like on the planet

The independent researcher James Lovelock, most widely known for developing the Gaia hypothesis, was contracted to NASA within the 1960s to build up atmospheric and planetary sensors for that Viking probes subsequently deployed to Mars in 1975.

Carrying out a precursory Earth-based assessment, Lovelock theorised the red planet was likely lacking of existence due to atmospheric chemical equilibrium. In comparison, Earths atmosphere is within dynamic flux because of the biological activity that can take place at first glance.

Notwithstanding the ongoing ambiguity whether or otherwise existence is, or ever continues to be, present on Mars, Lovelock set a effective precedent for that emerging field of astrobiology the comparative approach with Earth in the quest for extra-terrestrial existence.

Energy and existence

Within our endeavour to reply to the issue of whether we’re alone within the World, there exists a solitary clue: stick to the energy.

Earth is our only reference point, and existence on the planet requires energy thermal energy for melting water and chemical energy for maintaining existence. Thats it. Just two types of energy define the cosmic imperative for existence as you may know it.

But ironically, we don’t know when, where or how existence originated on the planet.

What we should can say for certain would be that the earliest and many abundant existence forms in the world are microorganisms. Biological adaptation isn’t restricted by structural simplicity, because microbes occupy every possible environmental niche on the planet.

When we accept the straightforward prokaryotic cell to be lifes universal blueprint, then ET is either a combination of microbes or perhaps is still a microbe.

Stick to the energy = stick to the water

The mandate to follow along with the power is symbolic of stick to the water. The current discovery of proof of liquid water on the surface of Mars thus remains intriguing, but there’s much more from it on Jupiters Europa and Saturns Enceladus.

These moons are compelling targets for astrobiology due to the inferred presence of oceans beneath a ocean ice crust which have endured over geological time scales.

A brand new interpretation of information collected through the Cassini spacecraft shows that the ocean beneath the ice on Enceladus isn’t just limited towards the south polar region. Like Europa, it’s global.


An artists rendering of Saturns moon Enceladus shows possible hydrothermal activity that could occur on and underneath the seafloor from the moons subsurface sea. NASA/JPL-Caltech

It now also seems that Europas ice shell comprises a mobile, plate tectonic-like system that overlies warm convecting ice along with a salty seawater reservoir that’s 30-35 occasions the level of Earths sea.

Should more water equal more existence? Not always. There are lots of biological constraints on habitability in extreme environments.

Existence as you may know it seems to become absent at first glance of Europa and Enceladus due to ionising radiation and very low temperatures. Photosynthesis as you may know it’s also most unlikely to happen under ice that’s kilometres thick.

Hydrothermal vents, a habitat for deep-ocean environments on the planet, might or might not exist around the moons.

Same with this the finish of comparison with Earth and finish of story? Really no, because its achievable that microorganisms that presently inhabit ocean ice on the planet may also inhabit the cold water-interface and ice fissures on Europa or Enceladus.

Existence in two opposites

The molecular grounds for adaptation isn’t completely understood, but extremophiles (microorganisms living in two opposites) must tolerate steep gradients in temperature, salinity, acidity and inorganic nutrients, in addition to dissolved gas and lightweight signatures.

Stress-related fissures within the ice shells of Europa and Enceladus are complex, and our knowledge of their topography is dependant on theoretical modelling. But fissures seem to positively exchange liquid in the subsurface oceans towards the ice exteriors.

The physiological demands on any microbial microorganisms could be exceptional, however these features could harbour small-scale, biologically permissive domains. Even brief periods of photosynthesis may be possible.

Extremophiles are relevant reference microorganisms simply because they adjust to multiple stressors with techniques we dont understand fully.

Existence on these moons is feasible, but exactly how likely could it be? The comparative approach requires an awareness of methods these microbes react to multiple stressors and also the limits that they may be pressed.

But the quest for extra-terrestrial existence is impeded because we lack a framework linking the capability for adaptation with ecological variability. Future research and exploration to those moons may benefit from experimental work that defines lifes limits within the ocean ice ecosystem.

Ultimately, we have to characterise theoretical biological limits which are dissimilar to the boundaries enforced on the planet-based analogues.

The ConversationAndrew Martin, Ocean ice microbial physiologist, University of Tasmania and Andrew McMinn, Professor of Antarctic Science, University of Tasmania

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