When the Hubble Space Telescope observed Mars near opposition in May, 2016, a sneaky companion photobombed the picture. Phobos, the Greek personification of fear, is one of two tiny moons orbiting Mars. In 13 exposures over 22 minutes, Hubble captured a timelapse of Phobos moving through its 7-hour 39-minute orbit.
Phobos may be a pile of rubble that is held together by a thin crust. It may have formed as dust and rocks encircling Mars were drawn together by gravity. Or, it may have experienced a more violent birth, where a large body smashing into Mars flung pieces skyward, and those pieces were brought together by gravity. Perhaps an existing moon was destroyed, reduced to the rubble that would become Phobos.
Hubble took the images of Phobos orbiting the Red Planet on May 12, 2016, when Mars was 50 million miles from Earth. This was just a few days before the planet passed closer to Earth in its orbit than it had in the past 11 years.