With much excitement, NASA announced the discovery of a bacterium, scraped from the bottom of California’s Mono Lake, that can thrive on highly toxic arsenic in place of phosphorus. The discovery would seem to widen the door on the types of organisms that astrobiologists might find elsewhere in the universe. “It’s like if you or I morphed into fully functioning cyborgs after being thrown into a room of electronic scrap with nothing to eat,” one researcher told The New York Times. Another noted that it “gives food for thought about what might be possible in another world.”
All fine and well and fascinating. Yet it’s worth noting that NASA has already discovered “alien” life, and it could well be living (if that’s the right verb) on Mars. Seriously. I wrote about this a few years back for Discover (and expanded on it slightly in the final chapter of Out of Eden), but it remains the single weirdest and most astonishing phenomenon I’ve come across in my years of writing about weird and astonishing things.
Long story short: NASA goes to great effort to scrub and clean its outgoing spacecraft, to make sure we don’t infect other planets with our germs. (As Kenneth Nealson, a University of Southern California geobiologist, once told Nature: “The field is haunted by thinking you’ve detected life on Mars and finding that it’s Escherichia coli from Pasadena.”) And it employs a microbiologist, Kasthuri Venkateswaran, to monitor how well these cleaning efforts are working and to document any microbes that survive the process. Many do, it turns out. When I last checked, Venkateswaran had identified 22 species of microbes thriving in JPL’s Spacecraft Assembly Facility, in other, similar NASA environments, even on actual spacecraft. Many are common to arid environments, like B. mojavensis, a bacterium that probably drifted in from the Mojave Desert. A handful are entirely new species. One, which Venkateswaran has named B. nealsonii (in honor of Kenneth Nealson), has two protective coats, making it a tough spore capable of surviving in the ultradry environment of the assembly facility. As Venkateswaran discovered, the second spore coating also offers a secondary benefit: It makes the organism unusually resistant to gamma rays, a form of cosmic radiation that, in large doses, is fatal to men and microbes alike. In short, the very traits that render these critters impervious to decontamination also grant them a decent chance of surviving the radiation shower they would encounter en route to and on the surface of a place like Mars.
His strangest discovery, however, was a brand new species of bacterium, which he named Bacillus safensis, because it found it in JPL’s Spacecraft Assembly Facility. He found the microbe thriving directly on spacecraft surfaces, presumably drawing its energy from ions of trace metals like aluminum and titanium. To protect themselves against desiccation, the individual cells form protective spores, which then band together to create what Venkateswaran calls an igloo. (In microphotographs, this spore house looks a bit like a macaroon.) When Venkateswaran cuts open the igloo, he finds no visible trace of the individual spores; they’ve all dissolved into the collective matrix. High-tech methods of life-detection reveal no evidence of life. But warm up the igloo and add a little moisture, B. safensis again springs into being. If the microbe is any indication of the sort of life that awaits discovery on Mars or elsewhere, Venkateswaran says, good luck to the robot sent to detect it.
In short, like an herbicide-resistant dandelion or the supertough microbes that sometimes spring up in hospitals, B. safensis evolved in and has adapted to the incredibly harsh conditions that NASA created expressly to eradicate it. It represents precisely the kind of organism astrobiologists are looking for in outer space. Indeed, it may already be there. Venkateswaran has found the bacterium in every other NASA assembly facility he’s studied; he found it on the Mars rovers Spirit and Opportunity when they were under assembly at JPL. Of course, they’ve been on Mars for some years now. B. safensis is almost certainly aboard them, alive and well, Venkateswaran told me at the time. “They could be there for millions of years because they are spores. Whether they will become active and begin terraforming -- that research is still ongoing.”
As NASA’s search for extraterrestrial life advances, it more and more resembles a trip through a hall of mirrors. The farther from Earth our gaze wanders, the more our very presence seems to nag us. Can we search for foreign life without contaminating it with our own? Can we discern the contamination from the real thing? If ultimately we’re related, if we’re all evolutionarily relatives from way back, is there even a difference? Some scientists wonder whether logic will permit us to find anything but ourselves out there: Our understanding of what constitutes life is shaded by what we know on Earth, so that’s all we know how to look for. It’s like that old joke about the guy who hunts for his keys under the lamppost because that’s where the light is.
The hunt for extraterrestrial life marks the ultimate test of humankind’s self-knowledge. We cannot find and recognize “other” until we can first, at the most basic cellular level, recognize “us.” Therein lies the true value of Venkateswaran’s microbes. Having found B. nealsonii, B. safensis, and their kin -- having in some sense fostered their creation and survival -- NASA has no plans to destroy them all. On the contrary, Venkateswaran intends to keep them alive as a sort of microbial archive for future reference. Someday, maybe soon, scientists will flip over a rock on Mars or Europa or somewhere out there and claim the profound, the first-ever discovery of “them.” How to tell for certain? We will hold up a mirror and compare appearances; that mirror awaits in Venkateswaran’s office. His microbes are us: our emissaries, our representatives, the reflection of our wily selves. Deciphering and confirming the distinction -- them or us -- will most likely take years. But as Venkateswaran sees it, those are precisely the hard facts that humans evolved to tease apart.
“It’s tough,” he says. “But that’s where our intelligence comes in.”
Just saying: You want alien life? We got some.
Originally posted at silvarerum.
