Life may be possible on planets devoid of water if they possess fluid mixtures of salts, known as ionic liquids, capable of hosting biological molecules like proteins. This is the suggestion of a new study from the Massachusetts Institute of Technology, published in the journal of the American Academy of Sciences (PNAS), which redefines the concept of a habitable zone.
“We consider water necessary for life because it’s what we need for life on Earth. But if we take a more general definition, we see that what we need is a liquid in which metabolism for life can occur,” states Rachana Agrawal, who led the study as a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “Now, if we include ionic liquid as a possibility, this can drastically increase the habitable zone for all rocky worlds.”
The researchers found that this particular type of fluid can form easily from chemical ingredients likely present on the surface of some rocky planets and moons. Ionic liquids are salts that exist in liquid form below approximately 100 degrees Celsius. The team’s experiments demonstrated that similar fluids can be produced from a mixture of sulfuric acid and certain nitrogen-containing organic compounds. Sulfuric acid on rocky planets could be a byproduct of volcanic activity, while nitrogen-containing compounds have been detected on various asteroids and planets within our Solar System, suggesting they could be present in other planetary systems as well.
Ionic liquids do not evaporate and can form and persist at higher temperatures and lower pressures than those tolerable by liquid water. According to the researchers, they can represent a hospitable environment for certain biomolecules like proteins.
Scientists hypothesize that even on very hot planets or those with atmospheres of too low pressure to support liquid water, there could still be pockets of ionic liquid. And where there is liquid, there could be the potential for life, even if it is likely different from the life we know on Earth.
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