Early Mars May Have Spawned Primitive Life
Mars in its early history was a warm planet with a much denser atmosphere than it has today, according to scientists who say the discovery constitutes strong evidence that the Red Planet could have supported some form of primitive life in its early years.
The scientists, reporting their findings in today’s issue of the journal Science, determined that hydrogen escaped from Mars’ atmosphere at a much faster pace in the early years than it does today.
“What this says is that the early conditions must have been very warm,” Tobias Owen of the State University of New York, lead author of the report, said in a telephone interview. The temperature on Mars today fluctuates wildly because of its thin atmosphere, ranging down to about 220 degrees Fahrenheit below zero.
The discovery should fuel a growing suspicion among scientists that Mars and Earth were very much alike during the first billion or so years when life began to develop on Earth. If life emerged so early on Earth, many scientists now believe, it could well have done so on Mars when conditions there were similar.
Other scientists said the new evidence could be especially important because it is based on a “very key number,” the ratio of hydrogen to its heavier isotope, deuterium.
“It’s one more piece of the puzzle that points to an early wet Mars,” said Andrew P. Ingersoll, a planetary scientist at Caltech. “It’s speculative, but maybe life could have evolved there.”
If life did evolve on Mars, it almost certainly would have required two things: water and warmth.
Scientists have long speculated that Mars once had abundant sources of water on its surface, as indicated by geological evidence of ancient rivers and shorelines, but it has proven a real challenge to determine the nature of the Martian atmosphere in those days, and no one is sure how long the water remained on the surface of the planet.
“Non-geological evidence for an early warm and wet climate on Mars has been lacking,” the scientists said in their report.
In an effort to better understand the evolution of the Martian atmosphere, Owen and the other members of his team, which included B. L. Lutz of Lowell Observatory in Flagstaff, Ariz., traveled to the highest major astronomical observatory in the world, Mauna Kea in Hawaii. The Earth’s atmosphere above the 14,000-foot peak is very thin, and more important, very dry.
Light emitted by or passing through various elements can be measured through spectroscopy, and the scientists used that well-established technique to study the water vapor in the Martian atmosphere.
“What we found was that the ratio of deuterium to hydrogen in the water vapor was six times greater (on Mars) than on Earth,” Owen said.
The dramatic shift in that ratio told the scientists that at some time the atmosphere on Mars must have been so dense that the heavier isotope--deuterium--was trapped and “only the lighter isotope (hydrogen) escaped,” he added.
Furthermore, the current escape of hydrogen from the Martian atmosphere can be measured, Owen said. By extrapolating back 4.5 billion years to the origin of the planets, the scientists determined that if hydrogen had been escaping at the same rate all those years, there never would have been very much water on Mars--certainly not enough to have created rivers and oceans that are believed--on the basis of geological observations--to have existed.
Key Conclusion
That has led Owen to one conclusion:
“The (hydrogen) escape rate must have been much higher in the past. It seems to us that the early atmosphere must have been thicker and warmer than it is today.
“This is the first time that we have had independent evidence” of that, he added.
There are many theories about what transformed Mars from a humid globe with rivers and seas to a dust bowl with dry winds whipping around the entire planet, sometimes at hundreds of miles an hour.
One possible explanation, Owen said, is that great quantities of carbon dioxide were absorbed out of the atmosphere into carbonaceous rocks, thereby making the air less dense. That would have allowed the lighter elements--like hydrogen--to boil off from the sun’s heat, thus reducing the amount of water.
Speculation on Water
Whatever the cause, Owen estimates that well over 80% of the water that was on Mars has since disappeared. The remainder is in the atmosphere as a very thin vapor and buried beneath the planet’s polar ice caps. Or possibly hidden deep beneath the surface.
The process that robbed Mars of its rivers and seas could well have taken a billion years or so, many scientists believe, and if that is the case Mars would have been very much like Earth during the years when life is now known to have been forming here.
Scientists have evidence that microorganisms formed on Earth when the planet was just a few hundred million years old, and the most basic cells may well have appeared when Earth was only tens of millions of years old.
Push for Research
That has led scientists to push for a renewed search for evidence of primitive life on Mars. U.S. scientists generally believe that any evidence would be, at best, the fossilized remains of life long extinct. Soviet scientists have said in international conferences that they believe microorganisms may still exist on Mars, possibly buried beneath the ground in permafrost.
Several programs are under way both here and in the Soviet Union to explore that area, including proposals by both countries to bring back rocks from Mars for laboratory analysis.
