Life? Nitrogen, carbon and hydrogen

Astronomers search for life in the so called circumstellar habitable zone (CHZ). The region where temperature and pressure allows for water to exist in some liquid form (also in subsurface oceans). What about life can exist even outside this zone?

Abandoning the liquid water requirement, thus enlarging the temperature-pressure range where life can exist might open plenty of new scenarios of extraterrestrial life.

In 1962 I. Asimov wrote an essay addressing a scenarios where he breaks down life-as-we-know-it beyond physiology debating the basic chemistry of life. Water, life support mechanism, is really fundamental? What could be possible in a world based on a different set of chemical compounds?

What about life not as we know it?

In our word, over-simplifying, life is a set of nucleic acid molecules controlling chemical reactions with proteins, using water as the base medium. Things can be different. Alternative xenochemistry can support life, made up of nitrogen compounds, in methane-rich environment where liquid water is not present. Such conditions resemble those of many (extrasolar) planets and moons; e.g. the liquid methane seas of Titan.

The study “Membrane alternatives in worlds without oxygen: Creation of an azotosome” recreated such alien life where “cell membrane, composed of small organic nitrogen compounds and capable of functioning in liquid methane temperatures of 292 degrees below zero” (here). So far on a pc, but new directions for search have been opened.


PS. Moreover, the liquid methane oceans of Titan seem to be not just static puddles. Recent Cassini images, indeed, show a “magic island” appearing and disappearing in these oceans.


It is not yet clear if it is an iceberg, terrain subject to tides, a radar dazzle caused by waves, or gas bubbles from the moon interior, but it is clear that these oceans are alive! Conditions for sure facilitating (this means energy) azotosome life.


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