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Deep Bacteria Hint at Life’s Ubiquity

From South Africa comes news of a striking find: bacteria living two miles beneath the surface and, more significantly, dependent only on the sulphur and hydrogen produced by geological processes rather than on the energy of the Sun. That life should form in such remote venues seems extraordinary, but the finding gives credence to the belief that similar microorganisms might have evolved on other worlds right here in our own Solar System.

Sure, we’ve found life in some hostile places before, including ocean vents and petroleum reservoirs, but their biological processes can all be traced at least partially back to the Sun, which provided the energy source for photosynthesis and therefore produced the needed nutrients for life. This new find, uncovered in a rock fissure that intersects the Mponeng gold mine near Johannesburg, uses radioactive decay as its power source, converting water molecules into hydrogen and ultimately producing hydrogen sulphide out of sulphate molecules in the rock.

Here’s Douglas Rumble (Carnegie Institution) on the process:

“We also believe that the sulfate used by these creatures is left-over from ancient groundwater mixed with ancient hydrothermal fluid. We can detect that because the chemical signature arises from interacting with the fracture’s wall rock. It is possible that communities like this can sustain themselves indefinitely, given enough input from geological processes. Time will tell how many more we might find in Earth’s crust, but it is especially exciting to ponder whether they exist elsewhere in the solar system.”

The microbes seem to have survived for tens of millions of years in this mode. Is there a similar kind of geologically-fueled life under the ice crust of Europa or in even more exotic environments further out in the Solar System? For that matter, how many other such communities exist elsewhere in our own planet’s crust? The paper is Li-Hung Lin et al., “Long-Term Sustainability of a High-Energy, Low-Diversity Crustal Biome,” now running in Science Vol. 314 No. 5798, pp. 479-482. An abstract is available.

Comments on this entry are closed.

  • Edg Duveyoung October 24, 2006, 14:37

    It is one thing for life to find a way to survive incredible hardships, but it is another to CREATE life in those conditions. I am assuming that these microbes do have DNA just like all the rest of life on earth, that it is left handed, that it evolved from other forms that were oxygen/carbon experts….like that.

    Maybe some planet out there has gotten an extra large helping of radioactive materials during it’s formation, and those planets that are out of the “water based life zones” could have a chance at evolving life from “scratch.” Doubt since too much radioactivity in the starter dough would generate so much heat that the oceans of earth would boil off and the crust would melt — a delicate thingy, eh?

    Then there’s Newton’s idea of beings living on the sun. That’s an idea I could write an essay about — I can see at least one way that that could be true.

    Always we’re talking far end of the spectrum chances on how life could evolve — silicon based life on a hot planet is possible they say — but, water based life seems to be much more often “offered” to the universe that I would put money on that being the “normal” life-from-scratch scenario. But, hey, am I water chauvinist? You bet!


  • Administrator October 24, 2006, 15:07

    I guess most of us are water chauvinists, but then there are always lively novels like David Brin’s Sundiver for alternate takes on these things. Given how surprising even our earlier exoplanet studies have been, I fully expect we’ll be surprised again once we actually get to environments like Europa or Titan, even if they’re only home to some exotic form of microorganisms.

  • Edg Duveyoung October 24, 2006, 16:25

    Underground Mars caves — mmmmmm, mmmmm, mmmmm! We’z a gunna get some legged thingies mebets!


  • Dennis October 24, 2006, 17:11

    We need constant temperature in this caves, above melting point. Say, hydrothermal or volcanic spots. Are they present on Mars? Who knows…

  • Edg Duveyoung October 24, 2006, 17:30

    Rock is a great insulator. Even 4+ billion years later, our earth still has a molten core, and there’s been at least some spritzing seen on Mars, some evidence of water less than a billion years ago, so something was warm then.

    Caves on earth have a fairly uniform temp of 54 degrees I think I read somewhere and they’re only a few miles “above” molten lava, so that rock insulation is pretty profound. Mars being so much smaller, loses heat much much faster, but still…..still, if life ever did get a foothold or pseudopod hold, whatever, I’d bet it would never die out — it’d find a way to survive — just as they think spores survived being smashed off of earth and into range of the outer planets. Earth could have seeded the whole system by now….or maybe Mars seeded us, eh? Maybe we’re Martians.


  • Gregory Benford October 25, 2006, 3:01

    Pleasant to see a prejudice confirmed!
    I wrote THE MARTIAN RACE, betting that life could hold out and evolve to high forms, amid the thermal vents and caverns of Mars. With lesser gravity, channels and pores are larger, affording more spacious life sites. The slow bleeding away of atmosphere and moisture is a good driver toward more complex lifeforms, able to sustain against hardship.
    The only way to test such ideas is to go and climb down–and robots can’t do nearly as well as two-legged human biologists. NASA could do this within a decade or two…but won’t.

  • Adam October 25, 2006, 8:43

    Hey Greg

    Did you see that recent “New Scientist” piece about bacteria being lofted into space electrostatically, then carried away by plasmoids detaching from Earth’s magnetotail? What do you think of the chances? That would be a very effective way to seed all the planets and nearby stars, I reckon. Alternatively it’s how we were, if we were, first seeded.

  • Administrator October 25, 2006, 18:59

    I’d also like to know about that panspermia notion you mention in New Scientist. It’s a bit of a jolt to see some of these once widely dismissed ideas coming back into serious circulation. It’s also a salutary slap at our preconceptions!

    The Martian Race, by the way, is wonderful. Any of you who haven’t read it should seek it out, as it’s as clear-headed a look at what we might find on Mars as I’ve seen. It’s also quite a good read, no surprise from Dr. Benford.

  • Adam October 26, 2006, 7:42

    Hi Paul

    The news piece was in the July 21st “New Scientist”. The researcher was Tom Dehel and he presented a paper at the COSPAR meeting in Beijing. He suggested that space adaptation is a consequence of atmosphere-living bacteria being lofted to the edge of space electrostatically. The existence of bacteria at the edge of space was demonstrated by that old panpermist, Chandra Wickramasinghe, though of course he thought the bugs sampled by high-altitude balloons were new arrivals. Dehel has now provided a mechanism for getting bugs up there.

    I just recently read “The Sunborn” (sequel to ‘The Martian Race”)and thought it was an excellent book – I loved the Plutonians and the plasma ‘beasts’ (did you borrow them from Arthur Clarke’s “Imperial Earth, Greg?) The idea of a magnetic being trapped in the conductive layers of Mars was also fascinating. The new finds from the mine make such things as a deep biosphere on Mars even more likely.

    Nice to think we might see traces of the Plutonians in 2015…

  • Zen Blade October 26, 2006, 14:23

    I haven’t read the martian race (it sounds interesting), but something about evolving to survive.

    For different organisms this is a response to different needs. These different needs are responded to with very different strategies with different outcomes.

    Survival, expansion of bacteria focuses (directly/indirectly) on streamlining the genome, keeping the genome smaller (by necessity), while maximizing the efficiency of energy usage. This translates to an organism with lower fidelity of DNA replication, and shorter generation times, which allows for far greater diversity… which feeds back into maximizing energy usage since there is such great diversity and competition.
    –a bacteria might be far more likely to evolve to form spores as the atmosphere is being drained away. It’s possible those spores could lay dormant for VERY long times and reawaken when conditions are more favorable. I recall something about anthrax spores being found in Egyptian tombs that were thousands of years old.

    Survival of other organisms (think animals) focuses on storage of information and making sure that the transfer from generation to generation has high fidelity–this requires a lot of energy. We want fewer mutations in our genome because we have much longer generation times, and far more cells. The creation/maintenance of one animal is a huge energy investment. Whereas the creation of a single e. coli is a much smaller investment and is only undertaken when there is ample amounts sources of energy present. E. coli generation time is less than 30 minutes in optimal conditions, even the quickest of mammals requires at least one month to reproduce–I believe–which translates to ~1000:1 generations (e.coli:mice).
    –so a large animal may see subpopulations becoming “dwarves” in order to survive. Or, the animal may try to adapt by entering a new environment, you could think about land mammals -> whales or land mammals -> bats.

    If hardship is coming, history tells us larger (“complex”) organisms are more likely to die first because they evolve/adapt much more slowely and are far fewer in numbers. If 90% of the e. coli in NYC die, not a big deal, the e. coli will be back to full strength in a couple hours or days. If 90% of the humans or rodents or pigeons in NYC die, it’s going to take a lot longer for them to recover.

    I think if hardship hit a planet like Mars, it’s very likely life would be sustainable, but we’re talking single cell organisms, maybe something larger, but I fear that would be unlikely.
    But who knows? You’ve got to do the experiment, right? We’ve got to get in those caves and look for stuff. If only I was a spelunker/caver! :)

    -Zen Blade

  • ljk June 5, 2008, 7:12

    New Species of Ancient Bacteria Discovered 2 Miles Deep in Greenland Glacier

    “Microbes comprise up to one-third or more of the Earth’s biomass, yet fewer than 8,000 microbes have been described out of the approximately 3,000,000 that are presumed to exist.”

    Jennifer Loveland-Curtze, Penn State astrobiologist

    Yet another Earthly extremeophile, a new ultra-small species of bacteria that has survived for more than 120,000 years within the ice of a Greenland glacier at a depth of nearly two miles has been discovered by a team of Penn State scientists.

    The microorganism’s ability to persist in this low-temperature, high-pressure, reduced-oxygen, and nutrient-poor habitat makes it particularly useful for studying how life can survive in a variety of extreme environments on Earth and possibly elsewhere in the solar system.

    This new species is among the ubiquitous, yet mysterious, ultra-small bacteria, which are so tiny that the cells are able to pass through microbiological filters. In fact, some species have been found living in the ultra-purified water used for dialysis.

    Full article here:


  • ljk June 13, 2008, 16:21

    “Intraterrestrials”: The Aliens Beneath Us – Solid Rock Dwelling
    Single Cells

    Terry Pratchett once described life as a simple, tiny “Yes” being said wherever it could. Even when the question is “Seriously, no, that’s impossible, are you SURE somebody isn’t just making you up?”

    Extremobiologists among you may have heard of (and been suitably impressed by) organisms clinging to existence under kilometers of ocean and enough pressure to turn you into “Internet reader soup” at the bottom of the sea.

    But it seems life always has another trick up its sleeve, and now scientists have found bacteria buried in tiny rock fissures hundreds of meters after even the sea itself gives up and stops.

    Full article here:


  • ljk June 15, 2009, 22:01

    ‘Resurrection bug’ revived after120,000 yearsNew Scientist Life June 15, 2009


    A tiny bacterium has been coaxed back to life after spending 120,000 years buried three kilometers deep in the Greenland ice sheet, beating a previous record of 8 million years (?). Researchers say it could resemble microbes that may have evolved in ice on other…



    Tantalizing clues to the chemical origins of life

    Nature News June 12, 2009


    An artificial DNA-like molecule that can change its sequence to bind to a DNA template without the help of enzymes has been created by researchers at the Scripps Research Institute. (Science/AAAS) The thioester peptide nucleic acid (tPNA) has a peptide (amino acid) backbone on which bases anchor, analogous to the sugar phosphates backbone…