“Supergiant” asteroid shut down magnetic field of Mars

May 12th, 2009 - 12:21 pm ICT by ANI  

National Geographic Washington, May 12 (ANI): In a new research, scientists suggest that a “supergiant” asteroid several times larger than the one that likely killed the dinosaurs struck Mars with such force that it shut down the planet’s magnetic field.

Based on the number of large craters present, scientists think very early Mars suffered 15 or so giant impacts within a span of about a hundred million years.

Now, according to a report in National Geographic News, a new computer model suggests that Mars’s magnetic field may have been slowly weakened by four especially large impacts and then snuffed out completely by a fifth and final blow.

“That impact created the 2,000-mile-wide (3,300-kilometer-wide) Utopia crater, which dates back roughly 4.1 billion years,” said study team member James Roberts of the Johns Hopkins Applied Physics Lab in Maryland.

“It’s possible that the four earlier impacts set everything up, and the Utopia crater was the straw that broke camel’s back,” he added.

Earth has a magnetic field in part because of heat transfer between the planet’s rotating molten core and the relatively cooler mantle layer above it.

This temperature difference helps create what’s known as an electric dynamo, which keeps the magnetic field stable over time.

But when the solar system was first forming it went through a tumultuous time known as the Late Heavy Bombardment, in which several large asteroids-remnants of planetary formation-smashed into young Mars, Earth, Venus, and Mercury.

“This is about the time the Utopia crater was formed, and roughly the same time that scientists think the Martian magnetic field shut down,” said Roberts.

According to the new model, the Utopia impact injected so much heat into the Martian mantle that it drastically reduced the temperature difference driving the dynamo.

“If the mantle becomes too hot, it’s not able to cool the core as efficiently, and there is no magnetic field,” Roberts told National Geographic News.

Without a magnetic field, Mars was exposed to the full brunt of the solar wind, the continuous stream of charged particles emitted by the sun.

The solar wind could then have slowly eroded away Mars’s atmosphere until only a wispy envelope of gas remained.

Drastic climate change would have soon followed, helping to create the desiccated Mars we know today. (ANI)

Tags: , , , , , , , , , , , , , , , , , , ,

Posted in Health Science |