SpicaBooks.Com/Life.html - Where Did Life Come From?

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7 Jun 04

Are We Really Martians?
January 13, 2000, by PAUL RECER, AP Science Writer

ATLANTA (AP) - Microbe-bearing rocks could have been ejected from Mars and seeded the Earth with life billions of years ago, or the exchange could have gone the other way, a study says.

"The question is, are we really Martians?" said Mauri Valtonen of the Turku Observatory in Turku, Finland, a member of an international team of astronomers and biologists who examined the question of whether primitive life forms could have been exchanged between planets.

They concluded it is theoretically possible.

In a study presented Wednesday at the national meeting of the American Astronomical Society, experts said their calculations show that if life ever existed on Mars then it could have been carried to Earth aboard some 5 trillion rocks blasted from the Red Planet by impacting asteroids.

The team also studied the possibility of microbe-bearing asteroids sailing into the Earth from solar systems beyond the sun. This probability was found to be very low.

"The ancestral cell for life on Earth must have originated somewhere in our own solar system," said Curt Mileikowsky, an astronomer of the Royal Institute of Technology in Stockholm and a leader of the research team.

In their calculations, the astronomers considered how frequently Mars would have been hit by asteroids powerful enough to blast rock away from the Red Planet and send it flying toward Earth. Although only a few Mars rocks have been found on Earth, the team calculated that tons of the material are here.

The team also calculated the pressure, temperature, acceleration and radiation a microbe would have to endure to live through a journey from Mars to Earth.

At least two well-known microbes, Deinococcus radiodorans and Bacillus subtilis, said Mileikowsky, would be capable of surviving the trip. He said the microbes have been tested in laboratories and found to be highly resistant to heat, radiation and acceleration forces.

Mileikowsky said to survive, a microbe would have to be near the core of a Mars rock. This would protect it during its journey through the vacuum of space and the searing fall to Earth.

"If the size (of the rock) is more than a football," he said, "heat would not have time to get inside."

The astronomers estimated that up to 1 1/2 percent of the microbes inside such a rock would survive.

The existence of life on Mars is now unlikely, but astronomers say that early in solar system history the planet had water, an atmosphere and mild temperatures. For this reason, it is believed that there once could have been Martian life. Scientists at the Johnson Space Center in Houston say they have found what they believe is evidence of ancient life inside a Martian asteroid, but the conclusions are controversial.

The experts also calculated that up to a trillion Earth rocks were blasted into space and traveled to Mars. This means Earth microbes could have journeyed to Mars.

"Because of the heavy traffic between Earth and Mars, we couldn't decide which came first," Martian life on Earth, or the reverse, said Mileikowsky.

In other research, a team of astronomers found that a primordial soup of complex organic chemicals that could be the precursors of life is cooked up very quickly after the birth of stars.

"Life could have had an easier time starting than we thought before," astronomer Sun Kwok said at the AAS meeting.

Kwok, of the University of Calgary, Canada, said a study by the Infrared Space Observatory showed that large organic molecules evolve within only a few thousand years from chemicals in the cloud-like envelope surrounding some stars.

Infrared spectra readings of short-lived, carbon-rich stars that are engulfed in clouds of gas and dust show that the clouds are rich in some of the most advanced organic molecules ever detected in outer space, Kwok said.

"There is no doubt now that such complex molecules exist and the stars are able to make them with no difficulty," said Kwok.

Such chemicals would eventually be ejected into interstellar space, he said, which makes it possible that they could end up on planets such as Earth where, under the right conditions, life could have evolved.

Among the chemicals detected was acetylene, a building block for benzene and other aromatic molecules that, in turn, can form complex hydrocarbons, the chemical stuff of life.

Kwok said it is possible that amino acids could be manufactured around stars, but this molecule, essential to life, cannot be detected by the current generation of space telescopes.

The Infrared Space Observatory is operated by the European Space Agency.

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	SpicaBooks.Com/Life.html 7 Jun 04
	*Are We Really Martians?* January 13, 2000, by PAUL RECER, AP Science Writer ATLANTA (AP) - Microbe-bearing rocks could have been ejected from Mars and seeded the Earth with life billions of years ago, or the exchange could have gone the other way, a study says. "The question is, are we really Martians?" said Mauri Valtonen of the Turku Observatory in Turku, Finland, a member of an international team of astronomers and biologists who examined the question of whether primitive life forms could have been exchanged between planets. They concluded it is theoretically possible. In a study presented Wednesday at the national meeting of the American Astronomical Society, experts said their calculations show that if life ever existed on Mars then it could have been carried to Earth aboard some 5 trillion rocks blasted from the Red Planet by impacting asteroids. The team also studied the possibility of microbe-bearing asteroids sailing into the Earth from solar systems beyond the sun. This probability was found to be very low. "The ancestral cell for life on Earth must have originated somewhere in our own solar system," said Curt Mileikowsky, an astronomer of the Royal Institute of Technology in Stockholm and a leader of the research team. In their calculations, the astronomers considered how frequently Mars would have been hit by asteroids powerful enough to blast rock away from the Red Planet and send it flying toward Earth. Although only a few Mars rocks have been found on Earth, the team calculated that tons of the material are here. The team also calculated the pressure, temperature, acceleration and radiation a microbe would have to endure to live through a journey from Mars to Earth. At least two well-known microbes, Deinococcus radiodorans and Bacillus subtilis, said Mileikowsky, would be capable of surviving the trip. He said the microbes have been tested in laboratories and found to be highly resistant to heat, radiation and acceleration forces. Mileikowsky said to survive, a microbe would have to be near the core of a Mars rock. This would protect it during its journey through the vacuum of space and the searing fall to Earth. "If the size (of the rock) is more than a football," he said, "heat would not have time to get inside." The astronomers estimated that up to 1 1/2 percent of the microbes inside such a rock would survive. The existence of life on Mars is now unlikely, but astronomers say that early in solar system history the planet had water, an atmosphere and mild temperatures. For this reason, it is believed that there once could have been Martian life. Scientists at the Johnson Space Center in Houston say they have found what they believe is evidence of ancient life inside a Martian asteroid, but the conclusions are controversial. The experts also calculated that up to a trillion Earth rocks were blasted into space and traveled to Mars. This means Earth microbes could have journeyed to Mars. "Because of the heavy traffic between Earth and Mars, we couldn't decide which came first," Martian life on Earth, or the reverse, said Mileikowsky. In other research, a team of astronomers found that a primordial soup of complex organic chemicals that could be the precursors of life is cooked up very quickly after the birth of stars. "Life could have had an easier time starting than we thought before," astronomer Sun Kwok said at the AAS meeting. Kwok, of the University of Calgary, Canada, said a study by the Infrared Space Observatory showed that large organic molecules evolve within only a few thousand years from chemicals in the cloud-like envelope surrounding some stars. Infrared spectra readings of short-lived, carbon-rich stars that are engulfed in clouds of gas and dust show that the clouds are rich in some of the most advanced organic molecules ever detected in outer space, Kwok said. "There is no doubt now that such complex molecules exist and the stars are able to make them with no difficulty," said Kwok. Such chemicals would eventually be ejected into interstellar space, he said, which makes it possible that they could end up on planets such as Earth where, under the right conditions, life could have evolved. Among the chemicals detected was acetylene, a building block for benzene and other aromatic molecules that, in turn, can form complex hydrocarbons, the chemical stuff of life. Kwok said it is possible that amino acids could be manufactured around stars, but this molecule, essential to life, cannot be detected by the current generation of space telescopes. The Infrared Space Observatory is operated by the European Space Agency.
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