why microbes hold the key to astrobiology

March 21, 2010

Bacteria are the most adaptable forms of life we know of, able to survive and thrive in everything from a boiling hot geyser, to a dark, subterranean chamber, and even in radioactive waters of nuclear reactors, though there is a limit on how much radiation they can absorb before their bodies break down. This radical diversity often means that wherever biologists look for traces of life in exotic environments on our world, they almost always find at least one strain of bacteria that happily lived there for tens of millions of years, and apparently, the vast real estate under the ocean floor is no exception. According to a story flying around major media outlets last week, as much as half of the planet’s entire biosphere might consist of various microorganisms buried under the ocean floor and feeding on such things as gases from thermal vents and minerals from the sediment.

Referred to as intra-terrestrial life, this biomass is particularly interesting to a number of researchers because it can shed light on how to find living things on Mars or Europa where any aliens would most likely thrive deep under the surface, in warmer environments close to geological hotspots. This is why the JOIDES Resolution, a scientific drill ship, will spend a year sailing across the Pacific and to the mid-Atlantic ridge, on a search for new microbes and tracking how they move through mazes of sub-oceanic aquifers by staining local colonies with dyes along the way. And there’s another notable point of interest for biologists here. On the one hand, life on our world could’ve started in remote, subterranean chambers and eventually moved upwards, closer to the shallow seas, hot springs, and other habitats, evolving photosynthesis while it migrated. Conversely, we can also propose that life began in the shallow seas and eventually finding its way down as new bacterial strains evolved to use the nutrients in volcanic vents, soils, and rocks to fuel its metabolism.

Studying microorganisms which may be ancestors of the hypothesized universal common ancestors in many evolutionary charts could give important clues to the validity of this theory and help us narrow down where life began. If half of all living things really make their home under oceans, continents and mountains, we need to find out why this is the case and apply what we can learn to the question of abiogenesis. After all, if we’re able to come up with a theoretically sound, evidence-backed model of how living things get their start in he kind of environments one would expect to find a newly formed planet, we’d be better equipped to either look for aliens on other promising worlds in our solar system, or construct models of how life may emerge in a very different set of conditions we could find on icy planets, moons and in other solar systems…

[ illustration by Hau Si Yuan Julian ]

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  • I think you should read some more chemistry books. TOday I read your comment on dad2059 blog in which you were claiming life forms usually may not be based on metals as they would be rigid and might not be as agile as that of carbon based one. you kmm know hardest material is diamond, and of course is carbon with sp3 hybridization. so where you stand. metals could significantly form more mobile life forms. good day, gfish!

  • Greg Fish

    Wow, that’s going back quite a while. I’m pretty sure what I was pointing out is that an alien using silicon instead of carbon as its primary chemical building block would be far more rigid than a carbon based creature due to the way carbon bonds form in the living things we know today.

    However, diamonds don’t form the same way DNA does. Instead, they’re subject to a great deal of pressure and heat deep underground for eons. This alters the way the carbon lattices are arranged. I really doubt you could have a living thing made of pure diamond since it would basically be a solid chunk of homogenous material.

  • bruceleeeowe

    Your mind is programmed to think only that way you have said already just as a calculater always respond 4 for 2+2, no matter how far you do in time dimension.

    Who is saying Diamond is alive? Graphite is another allotrope of carbon and soft enough and due to sp2 hybridization. So what matters is arrangement of atoms. That’s why I find it odd when you keep saying metal based life could be possible because it would be rigid and not be agile. Metal is hard and tough at NTP not at all conditions and this is not carbon which make us alive. Carbon has a high catenation property which make it capable of forming complex molecules. Metals could show such properties under right condition. Remember spider’s web,just another carbon based material, about 50 times more stronger than steel. So it is not hard to imagine a agile metal based life forms. Chemistry is based on observation. We can’t predict whether it would act in same manner as we expect.