[Added later: unfortunately Phobos-Grunt ain't landing nowhere. To say the least, a real disappointment.]
Phobos-Grunt will touch down on Phobos and return samples to Earth. If we expect the surface of low gravity bodies with organic materials (like asteroids and comets) is where we'll find evidence of von Neumann probes if they exist, then this is an exciting mission. "Low gravity" really means "low escape velocity", so life materials can spread more easily, and with an escape velocity of 40 kph, Phobos falls into that category.