Martian moon samples will have bits of Mars

A mysterious little rock in its own right

 The Martian moon Phobos has accumulated dust and debris from the surface of Mars, knocked into its orbital path by projectiles colliding with the planet. A sample-return mission to Phobos would thus return material both from Phobos and from Mars. Credit: NASA

A Russian mission to the Martian moon Phobos, launching in 2020, would return samples from Phobos that contain bits and pieces of Mars itself. A new study calculates how much Martian material is on the surface of Phobos and how deep it is likely to go.