Why don't we have potato-shaped planets?

Image | Europa

Caption: (NASA, ESA, W. Sparks (STScI), and the USGS Astrogeology Science Center)

This week our question comes from Martine Dennis, a listener in Orillia, Ontario. Martine emailed us with a question about the shapes of objects in space.
Are all planets and planetoids spherical? If so, are there stages t becoming spherical? Does dark matter "push" everything into spheres, or are the particles "pulled" together by the force of gravity?
To answer this question we reached Dr. Ray Jayawardhana(external link), a professor of physics and astronomy at York University
If you have a question get in touch: quirks@cbc.ca - Facebook(external link) - Twitter(external link)