The Mars Odyssey spacecraft has been orbiting the Red Planet since 2001 and since then has almost exclusively kept its scientific instruments focused on the Martian soil whose composition it is studying. It is only recently that NASA has implemented a reversal maneuver allowing the probe to change its line of sight and observe new things. It did just that in September 2017 for the first time when she was pointed at Phobos, the biggest of the two Martian moons.
Mars Odyssey reiterated a switchover on February 15, 2018 and this time under the lens of its THEMIS camera, a high-definition camera coupled to a spectrometer working in the infrared and visible light, appear Phobos but also Deimos, the second satellite of March. In the animation below, which compiles 19 images taken in an interval of seventeen seconds, the two moons appear side by side. Their apparent movement is due to the progression of the camera’s pointing and not to the movement of the two moons.
The two moons of Mars have long been studied by astronomers, but they still have their share of mysteries. To begin with that of their origin: two theories are opposed to this subject. The first estimates that the two satellites are two asteroids captured in the gravitational field of Mars. The other thinks they are the remnant of a giant impact that expelled Martian matter into orbit a few hundred million years after the formation of the planet. This last hypothesis seems to be gaining the support of the scientific community since the publication of two solid studies in 2016. The Japanese MMX mission (for Mars Moons Exploration), which is to bring Phobos samples back in 2027, will answer this question.