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Thursday, August 9, 2012

Extremophile Planet

The Red Planet

Like millions of other Earthlings, my heart thrilled as Curiosity made improbable contact with the surface of the Red Planet. The upright ape pries open another nut, I thought to myself. Our niche expands again.

The first photos from Mars look like turn-of-the-century pinhole camera images of an alien and exotic land. They suggest a window to a past, seen “through a shattered glass, darkly.” We are here to look for shards of the past, fragmentary glimpses of what once flourished here. Maybe Curiosity will tell us about life on Mars, and maybe Mars will tell us something about life on our own blue marble.

Mars appears blasted, utterly inhospitable. It’s easy to conclude that life made no start on this barren rock, that no spark ignited the complex dance of carbon. Life may be unique to Earth. But the more we learn about the Red Planet, the less ‘unique’ Earth seems to be. Like claims about humanity’s top rung on the four-legged hairy ladder of life, our place at the planetary table seems a little less secure. The boundary between us and them sidles ever closer.

First photos from Curiosi

Mt. Sharp : NASA
Mars has a lot in common with us, besides being a great home for our discarded electronics. Though its surface is now too cold and dry to support known life forms, it was once a wet place, with many of the conditions we hold sacred to life. Liquid water may still exist below the surface, and with it, simple microbes or photosynthetic bacteria.

Mars' south pole contains huge amounts of frozen water, and recent changes in craters and sediment deposits suggest that liquid water flows sporadically on the surface. Flash-flood gullies and subsurface geysers may offer a safe retreat for microbes and even simple plants, sheltering them from solar radiation. Scientists of some repute suggest that transient dark spots recorded in NASA’s fly-by imagery represent bacterial colonies. As springtime sunshine penetrates the ice, these organisms stir and photosynthesis begins. Pockets of liquid water form, protected from instant vaporization until exposed to the ruthless Martian surface. Once revealed, our cosmic brethren desiccate and blacken. 

Blasted Martian landscape
If life is a simple matter of electrified chemistry, we should find multiple births in life’s cradle. But every Earthling shares a common genetic ancestry, and it seems that the “vital spark from inanimate matter to animate life happened once and only once, and all living existence depends on that moment.” You can’t just zap the primordial soup and create life.There are a few more ingredients in our self-replicating confection.

The most fundamental is the cell membrane, collecting and concentrating life’s raw ingredients into tiny reactive beakers. Second, our inert bubble needs a spark: a source of energy to defy, at least temporarily, the laws of thermodynamics. Life must acquire energy rather than lose it if it is to find perpetual motion.

On Earth, bacteria break down molecules and consume their energy. The  methanogens eat methane and wash it down with water. Other bacteria dine on sulphur, or survive on water alone. These ancient children feed on the primal matter of Earth. These are the extremophiles, lurid “colored smears on the surfaces of rocks” that make their homes in Earth’s forsaken places: boiling sulfuric volcanic vents, lightless ocean seeps, and the scalding flatulence of explosive geysers. They are gifted problem-solvers from a time before the Sun’s power was unlocked, and rich subjects for Biomimicry. Chances are, if we find life on Mars, it will be a similar case of arrested development. In fact, our methanogens grow beautifully on simulated Martian soil. Who knows, maybe someday their extremophiles will inspire our innovations.
Possible water-formed gullies on Mars

On the third rock from the Sun, Earthlings went even further. By striking a flint on the now-ubiquitous green pigment, chlorophyll, they tamed fire. With each iota of light energy captured, a little green creature puffed a single breath of life-giving oxygen into the larval atmosphere, to be gobbled up by the oxidizers of this New World. They spread and puffed away, until finally, the photosynthetic bacteria produced oxygen faster than it could be locked away. Our original life-givers still quietly exhale today in the far-away acidic and saline lakes where grazing snails fail. Life creates conditions conducive to life, and so cooperation and collaboration were there from the beginning. Judging from our own planet, we might expect to find an entire interconnected ecosystem dining on light energy and methane just below the Martian surface. 

Polar ice cliffs: NASA/HiRISE Team
At some point, Earth’s inhabitants got vastly more creative still, and our evolutionary history radically diverged from the scientists’ most wildly imagined Martian fantasies. On Earth, multi-celled creatures evolved and invented sex. Today, most Earthlings scramble distinct sets of genetic information together and dole them back out in fresh combinations to their children, testing each one on our big blue lab.

Are we all Martians? Bobak 'Mohawk Guy' Ferdowsi
If we do find a Martian, what are the chances this rare mutation (life) occurred independently? Isn’t it more likely that our neighbor down the street is a sister from a different father, especially since our rovers idle at the Martian curb as we speak? Our ancient climates were similar: could life flit between them like finches in the Galapagos? A billion tons of Martian rock has surfed the cosmic current to our shores, and some microbes and even lichen can survive such space journeys. If life blew to Earth on a Martian wind, like dandelion fluff across the Pacific, the spark that binds us is still singular and special. Life remains “nothing less than the transformation of matter itself,” forging indifferent elements into a vital, self- regenerating system, the elusive perpetual motion machine. 

Such journeys evoke Columbus-era species-swaps, like Pocahontas’ descendants returning home from a life-altering vacation. Maybe all of us, from slime mold to spider to ape, are born of distant ancestors whose separated-at-birth children toil on beneath the Martian ice. You can’t help but think the ones left behind got the short end of the stick. How much more miraculous are Earth’s ecologies compared with even the richest Martian ecosystem? Where are the rainforests, with over 600 insect species in a single tree, each with a pocket penknife of surprising talents? Where on Mars will we find ten million species or more coexisting in bewilderingly interconnected networks? Where does life beget conditions conducive to life? Curiosity’s blasted vision suggests we won’t find it. “In the beginning, there was dust, and one day the great, improbable experiment of life will return to dust” and primeval cells like those we imagine on Mars will once again “spread their colored slime over the Earth, even as creatures of complexity and elegance know their last days.” Until then, let’s enjoy our vacation.

All quotes and much inspiration are from Richard Fortey’s fantastic evolutionary memoir, Life.