New York, Oct 31: Planetary scientists claim to have discovered new clues about the formation of planets in the solar system, from meteorites that are among the oldest rocks ever found on Earth. According to the scientists, the ancient meteorites contain magnetic records about the very early history of the planets, thereby solving mystery and overturning some accepted ideas about the way planets form.
In fact, they have based their findings on an analysis of pieces of three meteorites called angrites, which are among the most ancient rocks known.
The analysis showed that surprisingly, during the formation of the solar system, when dust and rubble in a disk around the sun collided and stuck together to form ever-larger rocks and eventually the planets we know today, even objects much smaller than planets -- just 160 kilometres across or so -- were large enough to melt almost completely.
This total melting of the planet-forming chunks of rock, called planetesimals, caused their constituents to separate out, with lighter materials including silicates floating to the surface and eventually forming a crust, while heavier iron-rich material sank down to the core, where it began swirling around to produce a magnetic dynamo.
The researchers were able to study traces of the magnetic fields produced by that dynamo, now recorded in the meteorites that fell to Earth.
"The magnetism in meteorites has been a longstanding mystery and the realisation that such small bodies could have melted and formed magnetic dynamos is a major step toward solving that riddle," Benjamin P Weiss, who led the team at MIT, was quoted by the 'ScienceDaily' as saying.
Until relatively recently, it was commonly thought that the planetesimals -- similar to the asteroids seen in the solar system today -- that came together to build planets were "just homogeneous, unmelted rocky material with no large-scale structure", Weiss said.
"Now we're realising that many of the things that were forming planets were mini-planets themselves, with crusts and mantles and cores," he said.
Bureau Report
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