LIFE ON VENUS ?
By Sean Henahan, Access Excellence
CO (2/5/97)- Although Mars has grabbed the headlines as a potential
site of extraterrestrial life, Venus may have been the original source
of life in our solar system, suggests a new book by a University of Colorado
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
Related information on the Internet
Excerpts from Professor Grinspoon's Book
NASA Education Site
AE: Primordial Soup
AE: More Clues to the Origin of
AE: Life on Mars?
Origins of Life- An Interview with Stanley Miller