Soviet Space Exploration Plans Fuel Scientific Interest in Life on Mars
The question of whether there is or ever was life on Mars has become a burning issue for a widening group of scientists, spurred in part by Soviet plans to explore that question in a series of ambitious missions to the Red Planet starting this summer and going into the next decade.
Scientists attending a three-day international conference that ended here Friday called for a renewed effort to search for evidence of primitive life on Mars despite earlier missions that left scientists with little reason to believe that life ever existed there.
The nagging question won’t go away, several scientists said, because the Earth and Mars are believed to have been very much alike in their early history when life began on this planet.
Clues on Ice?
Many scientists believe that the frozen soils of Mars might contain the best clues in the solar system to the origin of life, trapped and preserved in the very earliest stages of development.
A definitive answer to the question of whether there is or was life on Mars would require sophisticated new robotic vehicles that could roam freely over Mars--carrying out chores with little help or direction from Earth, making subtle distinctions between various geological structures and determining which rocks might be worth bringing back.
The Soviet Union plans to launch the first of a series of spacecraft to Mars this summer, and a subsequent mission will be designed to return samples to Earth. In the United States, the National Aeronautics and Space Administration is in the earliest stages of planning a similar mission, but that could not be carried out until the end of the century at the earliest.
Scientists attending the conference, sponsored by NASA’s Ames Research Center, said getting equipment to Mars may be the easiest part of all.
The Tough Part
Finding some evidence of primitive life, which probably exists in very few areas--if at all--would be the tough part.
Scientists are a little awed over the complexity of that task because it has been so difficult--here on Earth--to find fossils of primitive life forms. “Even if you are standing there, in the field, it is almost impossible” to know which rocks might be the most promising, said Don Lowe, a geologist with Louisiana State University.
Paleobiologists at the conference said the evidence that would most likely have been preserved would consist of “microbial mats,” structures that look like rocks but are in fact fossils of microorganisms deposited in thin layers, forming objects called “stromatolites.”
These ancient structures have been found in a few places on Earth, providing evidence of emerging biological activity that began when the planet was surprisingly young.
The earliest microorganisms probably developed “as soon as you had liquid water on Earth, within a few tens of millions of years,” said UC Santa Barbara paleobiologist Stanley M. Awramik. That would suggest life probably began here when the Earth was only a few hundred million years old.
Early Oceans
During its early history, Mars also had great oceans, as evidenced by erosion patterns there. Water on the surface of Mars may have existed until as recently as a billion years ago, scientists said, providing a possible catalyst that may have launched the biological process.
“If you have liquid water, inevitably you will have life evolve, and life as we know it,” said Hyman Hartman, a biochemist and computer scientist at UC Berkeley who argues that life probably began in moist, iron-rich clays.
Mars, however, did not retain its oceans. Some of the water is believed to still lie beneath the surface, but much of it probably evaporated into space.
“When the water disappeared, life ended on Mars,” Hartman added.
If he is right, then there should be evidence of that process somewhere on the planet. But “the odds of finding it are very remote,” said Awramik. Other scientists are equally pessimistic.
A trained professional working on the surface of Mars who ran across a microbial fossil “would only have about a 1% chance of recognizing it,” said paleobiologist Malcolm Walter of the Australian Bureau of Mineral Resources.
“There are many mimics” on Earth produced by the non-biological world that fool even the experts, he added, and that would surely be the case for Mars also.
An automated rover would have to make extremely subtle judgments on Mars, and it would also have to document the context in which the fossil was found in order for scientists to be reasonably sure that it is what it appeared to be.
“How do you program a rover as a field geologist?” Awramik mused during a public session Thursday night, hosted by the Pasadena-based Planetary Society.
Furthermore, scientists could not be sure of what the robot had found until after the rock was subjected to intensive laboratory analysis back on Earth.
That is a problem even on Earth. “In 90% of the cases, we can’t be sure even after we get back to the laboratory,” Walter added.
Question of Life
One curious departure between U.S. and Soviet scientists on the question of life on Mars is over whether life still exists there. Most American scientists believe that if life ever got started there, it has long since been wiped out. Soviet scientists repeated at this meeting, as they have elsewhere, that they are not so sure about that. A changing environment may have simply driven life underground where it continues to thrive, they argue. The Soviet rover will be designed to look beneath the surface for evidence of life.
“Mars is like our Siberian climate,” quipped Mikhail Marov, a physicist with the Institute of Applied Math. “But in Siberia, believe it or not, we even have human beings.”
