Estivating Universe

May 30, 2011

Panspermia is the notion that microbes can stowaway on space debris and ride a comet or meteorite from one environment to the next, seeding new areas with biology. This concept started out as merely curiosity among astrobiologists, but our understanding of panspermia has changed since the discovery of some unusual meteorites from Mars. The first these peculiar rock is the so-called Murchison meteorite that landed in Australia over 50 years ago. Scientists studying the rock found amino acids within the rock, the first evidence suggesting an extraterrestrial origin for some of life’s ingredients. Later on, a Martian meteorite found in Allan Hills, Antarctica catalogued as ALH84001 sparked controversy again when scientists believed that micro crystals of iron and carbon suggested remnants of life; since then, most of academia refutes these claims, but the possibility that microbes can hitch rides on satellites is still a very real possibility.

How likely is it that germs could survive a trip from Earth to Mars? Research suggests that this journey could take 100 million years one-way and that some forms of life can wait out that long period and be revived later. We know certainly that our biology can survive that time if properly shielded from the heat of entry and re-entry and the deadly radiation that would bombard it in transit. If a germ were protected by a thin layer of rock, it could ride out the journey from one world to the next with little problem. Germs can form spores that all but shut down their metabolism, leaving them inert for a while until the right environmental conditions start them up again. Not only single-celled organisms, but tardigrades, the so-called water bears can suspend their metabolism in a state of cryptobiosis until conditions are better for their survival. Not only can water bears induce a form of suspended animation, they can survive in near boiling temperatures, well below freezing, and can withstand over 1,000 times the amount of radiation that a human can endure. Water bears could be the most resilient animals on Earth. It’s certainly conceivable that his durable bug could be a pioneer on Mars, living in such a bleak environment as a Martian desert.

Could life have arisen on Mars when it was more habitable? And if so, could it have traveled to Earth? While Mars today is dry and barren, long ago it could have been habitable to life as we know it.

When NASA scientists cracked open an Surveyor 3 spacecraft after its sojourn in space, they found bacteria that had survived the vacuum of space for 3 years; the brutal environment of outer space didn’t kill that hearty germ, and so scientists began to talk about the idea of backward contamination. When the Apollo team first went up into space, NASA scientists were deeply concerned that the Moon might harbor viruses or germs that the Earthmen would have no immunity to; when their physicals came back clean, only then were they allowed out of quarantine. Since then, we know that the moon is very unlikely to harbor any kind of life, but the discovery that germs can ride out the vacuum of space leaves many researchers concerned that in the future, probes bound for potentially habitable abodes might contain Earth-borne germs that could colonize these exotic worlds and we could inadvertently spread life to the outer reaches of the solar system. The concern arises however, if we ever discover life out in our solar system; would our discover hail a genuine second origin, or are we just “rediscovering” Earth-life that relocated to a new habitat after we unwittingly contaminated a world with our germs? NASA has since taken huge precautions towards preventing both forward contamination of our research sites on Mars and beyond and backward contamination of any “Andromeda strain” of bacteria that we happen to take back to Earth with us.

What about deliberate panspermia? So far, the discussion has been about mistakenly spreading life, but what if we chose to deliberately seed the cosmos with our own biology? In the future, humans could build probes that would fly to other stars, carrying a payload of ready-made life that could set up shop on distant habitable planets. Our descendants could be fruitful and multiply throughout the universe in a scheme to colonize the universe like a celestial honey bee that pollinates across a vast field of stars.


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