The unusual properties of frozen water may have been the ticket that made life possible. Over the decades, several notable scientists have began to suspect that life on Earth did not evolve in a warm primordial soup, but in ice—at temperatures that few living things can now tolerate. The very laws of chemistry may have actually favored ice, says Jeffrey Bada, at the Scripps Institution of Oceanography in La Jolla, California. “We’ve been arguing for a long time,” he says, “that cold conditions make much more sense, chemically, than warm conditions.”
If Bada and others are correct, it would not only answer how life arose on our planet, but would dramatically change how we search for life in the Solar System and beyond. At that point, our chances of finding life elsewhere may be better than previously understood.
Life did not originate in Earth's subterranean depths, as some have contended, Bada argues, but rather on Earth's surface, where a primitive form of natural selection spawned the first genetic material.
Erupting geysers, intense wave action, lightning flashes, and blazes of sunlight that worked in combination with an atmosphere of methane, ammonia, hydrogen, and water vapor, to produce a primeval soup of the basic ingredients for the beginnings of life along with constant asteroid bombardment, killer tides, a lethal atmosphere, and a strange carpet of slime.
But what was the role of ice in the origins of life on Earth and possibly elsewhere in our Solar System and beyond?
Many who have studied the origin of life through the years have preferred to start with assumptions that make sense in today’s world. Today, life tends to thrive where it is warm. Consequently, scientists have imagined that life emerged in warmth, or even near boiling volcanic vents. However, like a love affair gone bad, it’s possible that conditions that would kill us now, were what nurtured our existence in the very beginning.
The late “cold theory” pioneer Stanley Miller challenged popular thinking with his new experiments and ideas. His students, and others, have continued in his footsteps with experiments indicating life may well have evolved well below the freezing point. Bada was a student of Miller who agrees that we could be been looking at things from the wrong angle.
Although life as we currently know it requires liquid water, small amounts of liquid can persist even at –60°F. Microscopic pockets of water within ancient ice may have gathered simple molecules, which assemble into longer and longer chains.
Matthew Levy, also once a graduate student of Miller’s and now a molecular biologist at the Albert Einstein College of Medicine in New York City. He recalls being handed one of Miller’s 25-year-old frozen samples to work on. The mixture of ammonia and cyanide represented conditions that scientists believe existed on early Earth and may have contributed to the rise of life. For 25 years, Miller had kept it as cold as Jupiter’s icy moon Europa—too cold, most scientists had assumed, for anything to have happened. What Levy found was that seven different amino acids and 11 types of nucleobases had formed.
“What was remarkable,” Bada says, “is that the yield in these frozen experiments was better, for some compounds, than it was with room-temperature experiments.”
Many were skeptical, and found their results too be “too remarkable”. Bada and Miller had to conduct more experiments before they could get their paper published in a reputable journal. The resistance the cold theory faced wasn’t surprising. Many chemical reactions slow down as the temperature drops, and according to standard calculations, the reactions that assemble cyanide molecules, for example, into amino acids and nucleobases should run a hundred thousand times more slowly at –112°F than at room temperature. By that calculation, even if Miller had run his experiment for 250 years—rather than the 25 he opted for—he should have produced nothing. However, things don’t always act the way we expect them to. Often the unexpected is what brings us the most incredible answers.
A young scientist named Alexander Vlassov may have accidentally found the answer of how tiny snippets of RNA became longer, well-crafted chains that could have acted as the very first enzymes. Vlassov was working at SomaGenics, a biotech company in Santa Cruz, California, to develop RNA enzymes that latch on to the hepatitis C virus. But his RNA enzymes weren’t behaving. They normally consisted of a single segment of RNA, but every time he cooled them below freezing to purify them, the chain of RNA spontaneously joined its ends into a circle, like a snake biting its own tail. As Vlassov attempted to correct the “glitch”, he noticed that another RNA enzyme, called hairpin, was also acting up. At room temperature, hairpin acts like scissors, snipping other RNA molecules into pieces. But when Vlassov froze it, it ran in reverse: It glued other RNA chains together end to end.
Discoveries like this shed new light on the prospects for finding life beyond Earth, especially with recent discoveries of geysers on Saturn’s icy moons Enceladus. too is suspected of having vast quantities of buried ice at its poles.
If life ever formed in one of these frozen areas, it might still exist there. On Earth, even areas that appear to be frozen solid harbor life. In the microscopic veins that permeate Arctic ice, for example, the high concentration of salt can maintain traces of water in a liquid state down to –65°F. Bacteria and diatoms survive in those minute “liquid veins”.
Hajo Eicken, a glaciologist at the University of Alaska at Fairbanks, suspects that similar conditions may exist in the lower, warmer layers of ice on moons like Europa. “There’s potentially hundreds of meters of ice, if not maybe a few kilometers, that may well be quite habitable,” Eicken says.
Another precedence would be the bacteria beneath films of liquid water only several molecules thick found clinging to microscopic grains of clay in ice cores from Greenland. Slowly consuming the iron in a single grain, these bacteria could get by for a million years before exhausting their food supply. At colder temperatures, where metabolic demands are lower, bacteria such as these could survive hundreds of millions of years.
“You’ve got to keep an open mind in this business,” Bada says. “If I were going to make a bet about what we’d find if we discover life elsewhere in the universe, I would suspect it would be more cold-adapted than hot-adapted.”
Posted by Rebecca Sato.
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Source Links:
http://www.astrobio.net/news/article1737.html
http://nai.arc.nasa.gov/news_stories/news_detail.cfm?article=titan.cfm
http://discovermagazine.com/2008/feb/did-life-evolve-in-ice
http://www.spacedaily.com/news/life-00za.html