Mars Was--and Is--Wetter Than Previously Thought
Mars, the arid and barren Red Planet, was a much more hospitable and humid place in its youth--not unlike primordial Earth, scientists at NASA’s Ames Research Center said Tuesday.
The planet appears to have perhaps 10 times as much water as previously thought--enough, they said, to cover the surface of the entire planet tens or even hundreds of meters deep. The water is now frozen in polar ice caps and permafrost or pooled deep underground, scientists theorize.
The presence of so much water, NASA scientists said, would make a human visit to the planet that much easier--and more desirable.
They discussed the new information and theories about Mars after a reanalysis of data from the twin Viking probes launched nearly a decade ago.
“The question of a manned mission at this point is a political question,” said Bruce Jakosky of the University of Colorado. “Certainly we now have the technology and the scientific justification to go.”
Water on the planet would supply astronauts with not only a way to quench their thirst during their expected year-long stay on Mars but also with oxygen for breathing and for fuel to burn--as well as for raising crops, according to Michael Carr of the U.S. Geological Service.
The scientists acknowledged that such conditions could have nurtured some form of life on Mars, but they cautiously noted that the conditions lasted “only” about a billion years; it took 2 billion years for life on Earth to evolve beyond simple one-celled animals.
No evidence of life--or even of the basic organic building blocks of life--was discovered by either Viking probe in the late 1970s and early ‘80s, an Ames spokesman said later.
In any case, the Martian climate changed radically as the planet cooled and volcanoes stopped recycling carbon dioxide into the atmosphere. Eventually the atmosphere grew thin, exposing the planet to very harsh temperatures, burning ultraviolet rays and the deadly effects of sunspots.
James Pollack of the space agency said he and his fellow scientists decided to restudy data from the Viking probes after a separate investigation of Venus showed that certain elements on other planets do not always occur in the same proportions as those on Earth.
That raised the possibility, he said, that previous calculations estimating the amount of water on Mars may have been incorrect, as they now believe.
The new theories were developed by NASA’s Solar System Exploration Division during a symposium at the sprawling Ames research facility last November.
In the meantime, scientists hope to test their theories about the Martian climate using the Mars Observer satellite scheduled to be launched in 1991.
The new theory about an abundance of water on Mars is supported by detailed studies of Viking probe data, including photographs of thin layers of sediment that appear to have been laid down in liquid water. Other photos show rocks apparently eroded by water.
Several years ago, researchers studying old radar data concluded that pools of water were hidden under the Martian surface. Scientists have long suspected that Mars’ prominent canals were carved by ancient rivers that had vanished, and that idea is consistent with the new theory.
The scientists at Tuesday’s briefing said Earth, Mars and Venus apparently were very much alike during Mars’ humid heyday 4 billion years ago.
“In a very crude sense, there was a great deal of similarity in the way they started,” said Carr, of the U.S. Geological Survey in nearby Menlo Park. “Probably the three planets were very similar in their composition.”
Distance From Sun
However, they were very different in size and distance from the sun, and that explains their radically different climates today, he said.
Mars, in particular, is much smaller than Earth--roughly one-seventh the volume--and is farther from the sun. This apparently has caused the planet to cool faster than Earth, and thus shut down volcanic activity.
“It (Mars) is a much smaller planet than the Earth, so there is much less energy to drive volcanic activity,” Pollack explained. He said it is unlikely that volcanoes will reappear on the planet.
One of the benefits of volcanoes, he continued, is that they recycle carbon dioxide. Natural chemical processes on both Earth and Mars leach that gas out of the atmosphere by incorporating it into carbonate rock. Lava from volcanoes decomposes this rock to release the carbon dioxide back into the atmosphere.
When Mars cooled and its volcanic eruptions ceased, the carbon dioxide pulled out of the atmosphere was not replaced. The effects of this drain on the Martian atmosphere of 95% of its carbon dioxide was tremendous.
No Liquid Water
Without an atmosphere dense enough to moderate the wild temperature swings found in space, water on the Martian surface exists either as ice or gas, but never as a liquid, the scientists said.
Some liquid water may be found half a mile beneath the planet’s surface, but “the evidence isn’t conclusive,” said Robert Haberle, a NASA scientist.
Nearly 4 billion years ago, however, scientists believe that snowdrifts belted Mars’ equator, rivers carved its famous canals and a few small oceans dotted its rocky, red landscape.
Knowledge about Martian geology and climate can help scientists studying the Earth, too, the NASA team said.
“What we’ve learned on Mars has given us tremendous insights on Earth,” said NASA’s Pollack.
“A lot of things going on in the Mars atmosphere also go on in the Earth’s atmosphere,” said Jakosky of the University of Colorado.
As an example, he cited evidence suggesting that Mars’ once-mighty rivers can be traced to a temporary 45-degree shift in the planet’s axis billions of years ago. He compared this tilt with a much less severe tilt in the Earth’s axis that is believed to have caused the Ice Age.
Data from Mars also can help decode the origins of other planets, including Earth, the scientists said.
“There are really substantial implications of how the (Martian) atmosphere formed and how the planet formed and what happened shortly thereafter,” Carr said.
