Why wouldn't they have floated away in the zero gravity of outer space?
As small as the comet is, it actually has a very small gravitational field. It’s incredible to think a rock that small has enough attraction to keep those rocks on the surface.
Interesting info about the failed Philae lander...
...the lander did not just touch down on Comet 67P/Churyumov–Gerasimenko once, but three times.
The harpoons did not fire and Philae appeared to be rotating after the first touchdown, which indicated that it had lifted from the surface again....it touched the surface at 15:34, 17:25 and 17:32 GMT.
The first touchdown was inside the predicted landing ellipse, confirmed using the lander’s downwards-looking ROLIS descent camera in combination with the orbiter’s OSIRIS images to match features.
But then the lander lifted from the surface again – for 1 hour 50 minutes. During that time, it travelled about 1 km at a speed of 38 cm/s. It then made a smaller second hop, travelling at about 3 cm/s, and landing in its final resting place seven minutes later.
That was my thought. The comet is traveling at 500 KM a second with very little gravity. You would think sand and rocks would be flying off it.
Best answer I got as to why = space is a vacuum so there is no resistance to make it fly off.
Very interesting still