Meteor bombardment may have made earth more habitable

June 2nd, 2009 - 5:21 pm ICT by IANS  

London, June 2 (IANS) Large bombardments of meteorites nearly four billion years ago probably made earth and mars more habitable by modifying their atmosphere.
When a meteorite enters a planet’s atmosphere, extreme heat causes some of the minerals and organic matter on its outer crust to be released as water and carbon dioxide before it breaks up and hits the ground.

Researchers suggest the delivery of this water could have made the earth’s and mars’ atmosphere wetter. The release of the greenhouse gas carbon dioxide could have trapped more energy from sunlight to make the two planets warm enough to sustain liquid oceans.

Imperial College-London researchers, analysed the remaining mineral and organic content of 15 fragments of crashed ancient meteorites to see how much water vapour and carbon dioxide they would release, when subjected to very high temperatures akin to the earth’s atmosphere.

The researchers used a new technique called pyrolysis-FTIR, which uses electricity to rapidly heat the fragments at a rate of 20,000 degrees Celsius per second, and they then measured the gases released.

They found that on average, each meteorite was capable of releasing up to 12 percent of the meteorites’ mass as water vapour and six percent as carbon dioxide when entering an atmosphere.

They concluded that contributions from individual meteorites were small and were unlikely to have a significant impact on the atmosphere of planets on their own.

The researchers then analysed data from an ancient meteorite shower called the Late Heavy Bombardment (LHB), which occurred four billion years ago, where millions of rocks crashed to earth and mars over a period of 20 million years.

Using published models of meteoritic impact rates during the LHB, the researchers calculated that 10 billion tonnes of carbon dioxide and 10 billion tonnes of water vapour could have been delivered to the atmosphere of earth and mars every year.

Mark Sephton, professor at Imperial’s Department of Earth Science and Engineering believes the study provides important clues about the earth’s ancient past.

The results were published in the journal Geochimica et Cosmochima Acta.

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