June 4, 2009

Earth more habitable because of meteorites

British scientists say large bombardments of meteorites four billion years ago might have made early Earth and Mars more habitable for life.

Imperial College London researchers said millions of meteor strikes during what's called the Late Heavy Bombardment approximately 3.9 billion years pelted Earth and Mars during a period of about 20 million years, possibly modifying the atmosphere on both planets.

Researchers explained that when a meteor enters a planet's atmosphere, extreme heat causes some of its outer crust minerals and organic matter to be released as water and carbon dioxide before it breaks up and hits the ground.

The researchers suggest the delivery of that water could have made Earth's and Mars' atmospheres wetter, while the release of the CO2 could have trapped more energy from sunlight to make both planets warm enough to sustain liquid oceans.

Using published models of meteoritic impact rates during the LHB, the researchers calculated 10 billion tons of carbon dioxide and 10 billion tons of water vapor could have been delivered to the atmospheres of Earth and Mars each year, for millions of years.

The study is detailed in the journal Geochimica et Cosmochimica Acta.