Ice layers record comet creation

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Ice layers record comet creation
By Paul Rincon
BBC News science reporter, in Houston, Texas



Comets hold materials unchanged since the Solar System's formation

The Deep Impact mission is casting new light on how comets formed and how they shed their ice in space.

The US space agency probe sent a 370kg projectile crashing into Comet Tempel 1 and then studied the plume of debris with its suite of instruments.

Nasa's mission scientists say images from last July's encounter reveal as many as seven different layers on the comet's surface.

Their results were presented at a major science conference in Houston, US.

Team member Mike Belton told the meeting he thought the layering was a sign of how comets like Tempel 1 were built up from lesser objects.

Growing 'snowball'

In the outer part of the early Solar System, smaller bodies called cometesimals collided and merged, gradually piling up to form the larger objects we know as comets.



Animated guide: Deep Impact

Similar collisions in the inner Solar System led to a loose accumulation of fragments that largely retained their internal structure.

But primordial material in the outer regions was travelling at relatively lower speeds and contained less solid material.

As the cometesimals hit the surface of a growing comet nucleus, they "flowed" on to the surface, researchers believe


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http://news.bbc.co.uk/2/hi/science/nature/4816712.stm

[FogerRox]

1. good stuff- K n R