Solar eclipses on Mars a Martian day is 24 hours 37 minutes long, meaning that Phobos can create two eclipses per Martian day. These are annular eclipses, because Phobos is not quite large enough or close enough to Mars to create a total solar eclipse. Deimos is too small (about ) and too far from Mars to cause an eclipse. The best an observer on Mars would see is a small spot crossing the Sun's disc. Both moons are too small to cast a shadow on Mars that can be seen from Earth. However, shortly after the first artificial satellites were placed in orbit
Moons of Uranus perturbations at apoapse cause the moons to acquire large eccentricities that lead to collisions with inner satellites or ejection. The lifetime of moons in the instability region is from 10 million to a billion years. Margaret is the only known irregular prograde moon of Uranus, and it currently has the most eccentric orbit of any moon in the Solar System, though Neptune's moon Nereid has a higher mean eccentricity. As of 2008, Margaret's eccentricity is 0.7979. The Uranian moons are listed here by orbital period, from shortest to longest. Moons massive enough for their surfaces to have collapsed into a