Life on Titan could eat acetylene

Artist's concept of a lake on the surface of the moon Titan

This artist concept shows a mirror-smooth lake on the surface of the smoggy moon Titan. Cassini scientists have concluded that at least one of the large lakes observed on Saturn's moon Titan contains liquid hydrocarbons, and have positively identified ethane. This result makes Titan the only place in our Solar System beyond Earth known to have liquid on its surface.

  • Chemicals are disappearing on Titan
  • Could be food for primitive life

Strange chemistry on Saturn’s moon Titan could indicate the presence of primitive life, say scientists.

While non-biological chemistry offers one possible explanation, some scientists believe the chemical indications bolster the argument for a primitive, exotic form of life or precursor to life on Titan’s surface.

One key finding shows hydrogen molecules flowing down through Titan’s atmosphere and disappearing at the surface. Another is that maps of hydrocarbons on the surface show a lack of acetylene, commonly known as welding gas.

The lack of acetylene is important because that chemical would likely be the best energy source for a methane-based life on Titan, said Chris McKay, an astrobiologist at NASA Ames Research Centre, who proposed a set of conditions necessary for this kind of methane-based life on Titan in 2005.

One interpretation is that the acetylene is being consumed as food. But McKay said the flow of hydrogen is even more critical because all of the proposed life mechanisms involved the consumption of hydrogen.

Titan as seen by the Cassini spacecraft

Saturn's moon Titan is very cold and smothered in hydrocarbon smog.

“We suggested hydrogen consumption because it’s the obvious gas for life to consume on Titan, similar to the way we consume oxygen on Earth,” McKay said. “If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from water-based life on Earth.”

Life in deep-freeze

To date, methane-based life forms are only hypothetical. Scientists have not yet detected this form of life anywhere, though there are liquid-water-based microbes on Earth that thrive on methane or produce it as a waste product.

On Titan, where temperatures are around 90 Kelvin (minus 283 degrees Celsius), a methane-based organism would have to use a substance that is liquid for living processes, but not water itself. Water is frozen solid on Titan’s surface and much too cold to support life as we know it.

“Scientific conservatism suggests that a biological explanation should be the last choice after all non-biological explanations are addressed,” said Mark Allen, principal investigator with the NASA Astrobiology Institute Titan team.

“We have a lot of work to do to rule out possible non-biological explanations. It is more likely that a chemical process, without biology, can explain these results—for example, reactions involving mineral catalysts.”

Adapted from information issued by NASA / JPL.

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