The thriller of the place Mars’s two moons got here from could lastly be solved. If Phobos and Deimos have been shaped when an icy object smashed into Mars, it may clarify their contradictory properties, which have lengthy baffled researchers.

Measurements of the geological make-up of Phobos and Deimos, together with tentative indicators of water, have prompt that they’re extra much like asteroids than to Mars itself, hinting that they might be captured asteroids. Nevertheless, that rationalization wouldn’t account for his or her round orbits, which as a substitute trace…