Updated on Tuesday, June 02, 2009, 11:49 IST

London, June 02: Large bombardments of meteoroids approximately four billion years ago could have helped to make the Earth more habitable for life by modifying its atmosphere, according to a new study.

A team at Imperial College London has based its findings on the analysis of data from an ancient meteor shower called the Late Heavy Bombardment, 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, researchers calculated that 10 billion tonnes of carbon dioxide and 10 billion tonnes of water vapour could have been delivered to atmospheres of Earth each year.

According to the researchers, this suggests that the LHB could have delivered enough carbon dioxide and water vapour to turn the atmospheres of the two planets into warmer and wetter environments that were more habitable for life.

However, according to the researchers, Mars' good fortune did not last. Unlike Earth, the Red Planet doesn't have a magnetic field to act as a protective shield from the Sun's solar wind. As a consequence, Mars was stripped of most of its atmosphere.

Lead author Dr Richard Court said, "Because of their chemistry, ancient meteorites have been suggested as a way of furnishing the early Earth with its liquid water.

"Now we have data that reveals just how much water and carbon dioxide was directly injected into the atmosphere by meteorites. These gases could have got to work immediately, boosting the water cycle and warming the planet."

Added co-author Prof Mark Sephton, "For a long time, scientists have been trying to understand why Earth is so water rich compared to other planets in our solar system.

"The LHB may provide a clue. This may have been a pivotal moment in our early history where Earth’s gaseous envelope finally had enough of the right ingredients to nurture life on our planet."

Bureau Report