ROSETTA DATA HINTS AT COMET FORMATION

New pictures from the Rosetta probe of the surface of Comet 67P reveal a lumpy texture in places that researchers speculate could have been the comet's original building blocks.
http://bbc.co.uk/news/science-environment-30931445

Cameras on Rosetta have now imaged 70% of the comet's surface. The unseen fraction, in the southern hemisphere, will be mapped as it emerges from the darkness of winter. The research team has defined 19 regions on the comet, giving each the name of an ancient Egyptian deity.

A striking occurrence is a kind of 'fluidisation' effect that acts to smooth some surfaces. Scientists think this occurs when ices change their structure. The change in phase results in a release of gas that can pick up local dust and make it move briefly like a fluid. Something similar is seen on Earth when large volumes of hot ash tumble down the sides of volcanoes.

It is obvious now that this comet is not a large lump of ice with some dust mixed in. It has a much more complex construction. incorporating significantly more dust and may rocky components. This is very evident from all those craggy cliff features where stiff, consolidated materials seem to dominate.

Simon Green of the Open University said: 'We used to think of comets as 'dirty snowballs'; we now think 'icy dirt-ball' is a much better description.. That's the way 67P looks - a solid object with ice vaporising from somewhere below the surface.'

Comment: It's clear from these latest published research findings that Rosetta is making important and exciting contributions to cometary science.