Comets could have kick started life on earth

April 29th, 2009 - 4:46 pm ICT by IANS  

London, April 29 (IANS) Comets could have supplied missing ingredients for the creation of life on earth, according to the latest study.
“When comets slammed into the earth about four billion years ago, they delivered a payload of organic materials that combined with Earth’s own large reservoir of organics and led to the emergence of life,” said Bar-Nun, professor of planetary sciences at Tel Aviv University (TAU).

Using a one-of-a-kind machine built at TAU, researchers were able to simulate comet ice, and found that comets contain ingredients necessary for providing the basic nutrients of life.

Specifically, Bar-Nun looked at the noble gases Argon, Krypton and Xenon, because they do not interact with any other elements and are not destroyed by terrestrial oxygen.

“Now if we look at these elements in the atmosphere of the earth and in meteorites, we see that neither is identical to the ratio in the sun’s composition. Moreover, the ratios in the atmosphere are vastly different than the ratios in meteorites which make up the bulk of the earth,” he said.

“So we need another source of noble gases which, when added to these meteorites or asteroid influx, could change the ratio. And this came from comets.”

Comets are essentially large chunks of ice, whose temperature ranges from minus 200 to minus 250 degrees centigrade. Formed in the early days of the solar system far away from the sun, water vapour condensed directly into ice, making little grains.

These grains came together to form the comets, which are about a km in diameter, explained Bar-Nun. During the comets’ formation, porous ice trapped gases and organic chemicals that were present in outer space, said a TAU release.

“The pattern of trapping of noble gases in the ice gives a certain ratio of Argon to Krypton to Xenon, and this ratio - together with the ratio of gases that come from rocky bodies - gives us the ratio that we observe in the atmosphere of the Earth.”

Thus, the arrival on earth of comets and asteroids between 4.6 and 3.8 billion years ago, led to the necessary ratio of materials for organic life, said Bar-Nun.

These findings were published in scientific journals including Icarus.

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