The science page of asteroids@home tells us:

"The results are asteroid convex shape models with the direction of the spin axis and the rotation period."

The comet Tšurjumov-Gerasimenko now filling the news is definitely not convex. It looks more like a rubber duck. Yes, I know that it is a comet, not an asteroid, but still I am curious
- are all asteroids convex
- is it theoretically impossible to detect non-convex asteroids or
- would it be an order of magnitude more heavy to compute a non-convex model?

regards
Markus

- Strictly speaking, all asteroids are nonconvex. The reason why all our models are convex is that the difference in disk-integrated brightness between a convex and a nonconvex body is small. There is simply not enough information in the photometry to derive reliable nonconvex models.

- In some cases non-convexities can be detected from photometry when they are large compared to the size of the body and when the body is observed at high Sun-asteroid-Earth angle (when the shadowing is important). The best way to reveal non-convexities is to have some disk-resolved data (images).

- It would be slower, but more importantly, it is not needed given the type and quality of the data we process.

For an example of a non-convex model derived from photometry look at asteroids Ivar or Eger in DAMIT (http://astro.troja.mff.cuni.cz/projects/asteroids3D).

Thank you!

Markus

Usually we see a block of rock on earth like a convex shape. If you melt several block of metal together you have as results a bigger block of metal. If you melt Under reduced gravity the same block you have as result a spherical shape. This is the main reason why the planets have a sphérical shape at their origin. But the rotation of the "molten planet" give him a flater structure at his rotation pole as at the ecuador. After cooling and became hardned planet you have a memory of the origins.Tectonik and falling asteroids change the face of the planets (crater, montains, vulcanos, liquids, or gaz appears trough such events.
Some asteroids could live at several degres such difference. I consider that the oldest asteroids without collision with other asteroids should be convex.

Also worth remembering that many asteroids are loosely bound aglomerations of smaller bodies of various shapes. Even large asteroids will not have enough gravity to collapse down to spheres.