Magnetic neighbours

Mars once had a magnetic field as strong as the Earth

Published: Thursday 31 October 2002

Unmasked: Martian surface (Credit: NASA)by extracting gases from inside the famous Martian meteorite alh 84001, researchers have revealed tantalising mixed news for people who believe that the planet could support life. The work suggests that Mars once had a magnetic field as strong as the Earth's.

alh 84001 was kicked off Mars 15 million years ago when some other body crashed into the planet. The meteorite landed on Earth 11,000 years ago. According to geologists from the California Institute of Technology, usa, an impact heated the rock four billion years ago. Since then, any magnetic alignment or gas in the rock was literally set in stone after it cooled.

To reach to their hypothesis, the geologists studied the alignment of an iron ore called magnetite, which reveals the magnetic record in a rock. The geologists assert that since alh 84001 has spent the past four billion years well below the temperatures at which magnetite realigns, its magnetic record must date from four billion years ago. After conducting many tests they determined that the strength of Mars' ancient field at that time was the same as the Earth's today.

Benjamin Weiss, who led the research, says that the magnetic field findings add weight to the theory that the meteorite contains signs of ancient magnetically orienting bacteria, but asserts that the chilly climate for Mars is "not very encouraging from the life perspective".

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