Tuesday, June 22, 2010

Life Keeps Popping Up Here and There

by Richard Crews
When I went to high school (in the middle of the last century), I learned that all life--and I mean ALL--depended on energy from the Sun. Through the miracle of chlorophyll, sunlight charged up delicate organic chemicals which could then be used to fuel growth, tissue repair, reproduction and the seven-or-so key abilities that all living things can do, and no non-living things can do. Basically if you weren't green (with chlorophyll), you ate somebody who was green--or maybe you ate somebody who ate somebody who was green. Somewhere back in your food-chain base you got energy for life from the Sun.

Then in 1977 scientists discovered deep sea vents--essentially under-water volcanoes that spewed out hot chemicals. And these vents had ecosystems around them that never knew light from the Sun. Complicated ecosystems with networks of plants and animals. Moreover, as explorations proliferated, it turned out these ecosystems were enormous--a total mass of living beings worldwide that far exceeded the mass of chlorophyll-dependent life: the forests and fields and animals and bugs we had thought was all there was to life.

Other ecosystems were discovered (1985) deep in the Gulf of Mexico that get their energy from oil seeping up through the seafloor bed. (Granted, the energy in this oil came originally from chlorophyll-trapped sunlight, but that was so many millions of years ago that only a purist would quibble with the novelty of it.) Other explorations (2006) turned up organisms tucked away deep in a South African mine, organisms that use radioactive decay of uranium and thorium as their only source of energy.

Life, it seems, will spring up around whatever energy source is available.

What about the dilemma that only life can make life (at least until a few months ago when a computer with a few bottles of chemicals finally managed the task). How on Earth can the life-making-life process ever have gotten started? Not too tough a question after all, since it turns out that inter-stellar space is rife with complex organic chemicals--they are raining down on the planet all the time.

Along the way scientists also found the most adventurous "extremophiles," organisms that thrive in boiling hot battery acid; or in water so salty it would float a penny (well, not really, but I was looking for an impressive metaphor here); in microscopic cracks in rocks miles beneath the surface of the Earth; and in all manner of hostile environments.

The moral of this story is that life keeps popping up everywhere. Will it be found in the oceans of Jupiter's satellite Europa? Probably. In the rocky crystals on Mars? Probably. On some of the hundreds of exoplanets now being studied that are circling stars outside of our solar system? Probably.