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Bacteria discovered in lake of oil: implications for extraterrestrial life?

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A recent discovery by scientists may have implications for possible extraterrestrial life: bacteria have been found thriving in a lake of oil in Trinidad, again showing how life can exist in even the most inhospitable conditions on Earth. The discovery brings to mind the similar environment on Saturn’s moon Titan, where lakes and seas of liquid hydrocarbons (methane/ethane) exist at the moon’s poles.

The new findings were just published in the journal Science by an international team of scientists who studied Pitch Lake, a natural liquid asphalt lake in Trinidad, and found microorganisms (bacteria and archaea) living in tiny water droplets within the oil deposits. There is relatively little water in the lake, so the discovery of such a thriving ecosystem was unexpected. Yet these miniscule water droplets are apparently more than enough to sustain microbial life within them, even though the surrounding oil is full of toxic compounds.

“Oil was considered to be dead,” according to lead study author Rainer Meckenstock, an environmental microbiologist at Germany’s Helmholtz Zentrum München. “The microbes most likely were enclosed in droplets in the deep subsurface and ascended together with the oil.”

The water droplets are also highly salty, and their isotopic composition suggests that the oil originates from deep in the subsurface below the lake. On the surface of the lake, methane bubbles are also released into the atmosphere, after microorganisms have altered the chemical composition of the oil, which rises up to the surface from the lake bottom.

There is a place in the Solar System which has conditions similar to this: Saturn’s largest moon Titan. The environment is much too cold for liquid water on the surface, but instead there are lakes and seas of liquid hydrocarbons, methane, and ethane. There are even rivers and rain—Earth-like in appearance but very different in composition. But since these are bodies of liquid, it has been questioned whether some form of life could exist in them, perhaps methane-based. The idea is a tantalizing one, even if still just speculative.

The extreme cold is certainly a limiting factor, but the results from the lake in Trinidad show that the possibility shouldn’t be discounted. The Titanian lakes may also contain tiny droplets of water, which would otherwise be frozen solid on the ground. We just don’t know until another mission can go there and examine them up close. Or perhaps life could do just fine in the lakes themselves and not even need water.

Titan’s atmosphere also contains a lot of methane, and the source of it is still unclear. While scientists know it is being regularly replenished, it is assumed by most that it is geological in origin. What if bubbles of methane were also being released into the atmosphere from the lakes and seas in a way similar to the lake in Trinidad? Purely hypothetical at this point, but interesting to think about.

There is also the previous finding that hydrogen, abundant in Titan’s atmosphere, seems to somehow disappear at the surface, as if something is consuming it, like what happens on Earth with nitrogen/oxygen. Some scientists have suggested this might be evidence for life of some kind, although there are still other explanations possible. Titan is a very mysterious and alien world.

Adding to the possibilities, there is now thought to be a subsurface ocean of salty liquid water deep below the surface of Titan, something like Europa or Enceladus. Even if the surface is completely devoid of life in such harsh conditions, this ocean may be a more suitable habitat. Very little is known so far about the actual conditions down there, so again everything is conjecture until we can return to Titan and explore it better with more advanced probes.

The abstract/paper is available here.

This article was first published on AmericaSpace.

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