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LIFE ON VENUS ?
By Sean Henahan, Access Excellence
Four billion years ago the sun was 40 percent cooler than today. During that time, Earth and Mars probably were frozen. Venus, however, is closer to the sun, and may have had warm liquid oceans and a mild climate at the time, notes CU-Boulder Assistant Professor David Grinspoon of the astrophysical and planetary sciences department. "There is some reason to believe Venus may have been the best haven for life in the early solar system," he said. With 900 degree Fahrenheit surface temperatures and an atmosphere permeated by carbon dioxide, chlorine and sulfuric acid clouds today, Venus seems inhospitable to "our kind of life," he said. "But we really don't know much about life -- its requirements, it's differences and how to recognize it." It is even possbile that life on Earth may have evolved from life forms provided by Venus, Grinspoon said: "Pieces of planets were blasting off of each other all the time early in the evolution of the solar system, and microbes from Venus could easily have wound up on Earth." While the standard scientific view is that life requires water and carbon-based molecules, it cannot really be said if that is the only chemical system that can make life, said Grinspoon, who has been studying the surface, atmosphere and clouds of Venus for 10 years through NASA-sponsored programs. Indeed, Venus may have a better environment for nurturing life than Mars, he said. Like Earth, Venus has a chemically lively surface and atmosphere that could provide organisms with energy and nutrients. "In my view, what makes Earth special is its atmospheric cycles that renew themselves like a garden tilling itself," he said. "It could well be that kind of an environment on Venus is just as important for life as carbon." Because the surface and atmosphere of Venus are constantly renewing themselves through volcanic activity, there is more potential for interesting chemical and even biochemical processes on Venus than on Mars, he said. "It's possible that Venus could have tiny microbes in its cloud particles, or that some form of Venusian life could have developed by using ultraviolet light much like Earth's plants use sunlight to make food. There could even be a non-carbon-based equivalent to lichens atop Venus' five-mile-high volcanoes, perhaps feeding on sulfur gases," he said. The interactions of Earth's oceans, clouds, surface and biosphere has led some scientists to propose "the Gaia theory", that Earth itself is a living system. "By constantly exhaling sulfur gases that react with the clouds and surface minerals, Venus could be considered in that Gaia realm," notes Grinspoon. Although NASA's 1989 Magellan probe opened a new window on the planet using sophisticated radar mapping, there is still much to learn about Venus, said Grinspoon. One key is to keep an open mind about chemical and perhaps biological processes that may be occurring there and on other planets. "Venus is the closest thing Earth has to a twin," he said. "Studying Venus is how we learned about the problem with our ozone layer, and it's a way for us to become wiser in taking care of our own planet." Related information on the Internet Spacelink: NASA Education Site AE: Primordial SoupAE: More Clues to the Origin of Life AE: Life on Mars?
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