Toronto: A group of astronomers in Canada have suggested that an orbiting asteroid may have switched Mars's magnetic field on and off like a light switch.

Mars once had a magnetic field, which may have been driven by a dynamo formed from the convection of material in the core, much like the Earth's is today. Yet crater records suggest the Martian dynamo died quickly, over a few tens of thousands of years, something researchers struggle to explain, the New Scientist online said.

According to the report, Jafar Arkani-Hamed of the University of Toronto, Canada, and colleagues now say the gravitational tug of an orbiting asteroid may have powered a dynamo by pulling on the fluid in Mars's core. Asteroids, also called minor planets or planetoids, are Solar system bodies smaller than planets but larger than meteoroids (which are commonly defined as being 10 meters across or less), and that are not comets.

The team's lab and model simulations showed that an asteroid orbiting 75,000 kilometres above Mars could have maintained a dynamo for 400 million years, before the rock crashed into the planet and switched it off. The report said an asteroid could have done just that to Mars 4 billion years ago.

However, some researchers are sceptical. While an asteroid might have had enough energy to churn fluid in the planet's core, much more energy is needed to set up the dynamo to begin with, according to David Stevenson of the California Institute of Technology in Pasadena. "It would be like looking at a boulder on top of a hill without asking what it took to get it there," he said.

Source : PTI