ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Saturday, October 26, 1996 TAG: 9610280070
SECTION: NATL/INTL PAGE: A-1 EDITION: METRO
DATELINE: TUCSON, ARIZ.
SOURCE: Associated Press
Mars is throwing rocks at us. Tons and tons of rocks, scientists say. But there's no need to dive for cover. Most of them miss.
``There is stuff coming in from Mars every month,'' said Joseph Burns, a Cornell University astronomer who has studied meteorites and presented a paper on his research at this week's national meeting of the American Astronomical Society's planetary division.
And some of the Martian chunks in the past could have seeded the Earth with life, he said. His research gives some support to the long-held speculation that Mars was the cradle of life on Earth.
Most Mars rocks heading to this planet are small enough to burn up in the Earth's atmosphere on the way in. Many others splash unseen in the oceans. But of about 17,000 known meteorites found on Earth, 11 have been identified by chemical analysis as coming from Mars. Among these is one that NASA scientists say contains fossilized evidence of ancient life on Mars.
Rocks of all sizes, from mountain-size boulders to tiny pebbles, have been whizzing around the solar system for billions of years like balls in a pinball machine.
Most meteorites seen streaking into the Earth's atmosphere, such as the one that created a light show over Texas and California this month, are asteroids that were never part of a planet.
Every now and then, one of these rocks smashes into a planet. Mars has no atmosphere to burn up such intruders, and therefore is more subject than Earth to get hit, hard.
If the rock crashes into a planet with enough speed and force, it explodes the surface like a bomb. Bits of the planet itself are splashed in every direction, sometimes sailing right into space.
Rocks splashed from Mars will go into the red planet's orbit if they are accelerated at about 33,000 mph. Once in orbit, these bits of Mars become like the other space rocks - balls in that celestial pinball game. Gravitational forces of the solar system planets play with the rocks, sending them first one way and then another. Some collide with another planet or the sun.
About 7 percent of Martian rocks knocked away from that planet eventually hit Earth, Burns said, while more than 30 percent eventually burn up in the sun. Other bits would hit Venus, Mercury or be sent out of the solar system after a gravitational boost from the sun.
The idea that Mars was the cradle of life has long been a speculation because it is believed that the red planet was actually more conducive for life formation early in its history than was Earth, said Alan Treiman of the Lunar and Planetary Institute.
Burns said his research shows that some Mars rocks could have arrived at Earth loaded with living forms of life. He estimated that about 1 percent of the Mars rocks hitting Earth arrive just six months after being jolted from the red planet.
``Studies have shown that microscopic life can survive in space for at least six months,'' Burns said.
For example, a test satellite left in orbit more than a year and then brought to Earth was found to contain living microbes. Specimens collected by Apollo astronauts from a robot craft - sent to the moon years before the manned landings - was found to contain Earth microbes that survived their long stay on the lunar surface.
That means the Earth may already have had visitors from Mars, said Burns.
``If there was life on Mars, it is quite likely that some of it reached Earth'' and could have seeded the Earth, he said. ``It could be that we are the little green men from Mars, having originated on that planet.''
Not only is it thought that Mars once was more conducive to life creation, but early on, there were more Mars rocks being knocked into space and, hence, a greater chance for life-bearing Martian samples to arrive at Earth, he said.
``They, in effect, could have inoculated Earth with life,'' Treiman said.
LENGTH: Medium: 74 linesby CNB