The Philae lander has touched down and remains on Comet 67P. Its landing gave a surprise as it seems to have sank about 4cm into the surface, after bouncing up and back down from the initial impact.
Was the landing on an ice mountain covered with dark dust, that would explain its very dark colour? A thick layer of dust for Philae to sink below the surface?
Would it be a relatively thin layer covering a hard surface, as Philae bounced back up of the surface, or would it have always bounced up due to the very low gravity and that its thrusters/harpoons didnt work?
Comet 67P still a dusty snowball?
The initial image released of its approach seems to show a rocky landscape with stones, boulders embedded in dust or dirt, as the rocks seem to protrude from the covering. It is unlike most dirty snowballs or ice mountains.
If it is dust/dirt then how would it get there? How would it be produced and stay on the surface of the comet?
Would the dust/dirt have got their from the EDM (Electrical discharge machining) of the comets surface material, as seen in the comets 'jets' and its surprising geological features like craters and cliffs?
Would it be held to the surface by some form of electromagnetic force, similar to static electricity?
The superb news is that we now do not have long to wait for answers and then a lot more questions and debate.
Why is Comet 67P surface so dark?
"The prevailing assumption is that it is the presence of organics at the surface," says Prof Jessica Sunshine, who's been a leading investigator on Nasa's recent comet flybys.
"We think the comets weren't always this dark," says Ptolemy principal investigator Prof Ian Wright, "but after several passages around the Sun, the organics have become concentrated at the surface as ices have sublimed away.
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