Phobos and Deimos
Phobos
Phobos is a moon of Mars and was discovered by Asaph Hall in 1877. Phobos was named after an attendant of the Roman god Mars. Its name means "fear". It is similar to the blackish carbonaceous chondrite asteroids that are in the outer asteroid belt. Some scientists believe that Phobos is an asteroid captured by Mars' gravity. However, other scientists are not so keen on this idea. Phobos shows patterns which are probably cracks caused by the impact event of the largest crater on its surface. This giant crater is called the Stickney crater. Its escape velocity is 0.0103 kilometres per second. Its mean distance from Mars is 9,380 km.
Deimos
Deimos is a moon of mars that was also discovered by Asaph Hall in 1877. Deimos was also named after an attendant of the Roman dog Mars. Its name means "panic". Some scientists believe that Deimos was a captured asteroid but other scientists disagree with this theory. Deimos' surface is smoother than Phobos' surface. Its escape velocity is 0.0057 kilometres per second. It's mean distance from Mars is 23, 460 km. Deimos circles Mars every thirty hours.