The Earth got its Moon when a celestial object collided with our planet more than four billion years ago. This impact hurled molten rock into space, which eventually coalesced to form the satellite we can see every night from across our planet.
But what of our neighbour, Mars? The red planet has two small, irregularly shaped moons called Phobos and Deimos. There are several theories on how these natural satellites formed, but no clear front-runner. Soon, a Japanese-led space mission called Martian Moons Exploration (MMX) will begin its hunt for the answer.
