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Science Frontiers ONLINE No. 107: Sep-Oct 1996 |
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Rock-Based Life
Virtually all biology textbooks insist that all terrestrial life ultimately depends upon sunlight for its survival. The ecosystems clustered around the deep-sea vents and the bacteria found in deep aquifers demonstrate that the sun is not essential to life -- chemical energy does just fine.
In fact, the domain of chemosynthetic life has now been extended to a Romanian cave that has apparently been almost completely sealed off from surface influences for 5.5 million years. Air does leak in through tiny cracks, and water partially fills the cave. What is most remarkable in this sunless, sealed ecosystem is its biodiversity: 48 animal species, including 33 brand-new species. The roster includes isopods, a millipede, a centipede, a water scorpion, and a leech. Of course, bacteria and fungi thrive there, too.
In contrast to unsealed caves, where insects, bats, and other sources of food filter in from the surface, life in the Romanian cave seems to derive entirely from hydrogen sulfide present in the cave's rocks. This compound is consumed by microorganisms, which are then grazed by cave occupants higher up the food chain. A NASA scientist has called Movile cave a "Mars analog site." And indeed it might be, for Mars has plenty of rocks and subsurface water.
(Skinrud, E.; "Romanian Cave Contains Novel Ecosystem," Science News, 149: 405, 1996)
Comments. Fluid-filled cracks and pores extend miles down below the earth's surface. It would be surprising if novel ecosystems do not exist there, too. The ice-sealed Antarctic lakes (see next item under GEOLOGY) may also surprise biologists. As for outer space -- a realm pulsing with energies of many kinds -- we can imagine that matter has assumed many unfamiliar forms, some of which we might call "life."