Hello Unity Community, i am making a 2D SpaceGame Where you need to land on a planet!

and i am trying to create this planet but i am struggling, Because The planet needs to have loads of hills and stuff, And There has got to be a collider on the planet, is there anykind of software out there that could help me? A bit like shown is this image http://inventwithpython.com/blogstatic/lunarlander.png?27f655