Deimos is a tiny moon of Mars, perched right on the edge of high Mars orbit.
It is believed to be a captured C-Type asteroid; although nobody has any idea how it got to be there, or Phobos either for that matter. Any higher and it would have been destabilised by the tidal effects of the Suns gravity and left Mars entirely.
Other facts about Deimos is that it is very 'close' to the earth on the way back, less so on the way out. (By close I mean that the amount of propellent to return to the earth-moon system is small, as the return delta-v is only about 2.6km/s; and to travel there is about 6km/s; for comparison it takes about 9.5 km/s to get to low earth orbit from the earth; even a very tiny rocket can achieve 2.6km/s with ease. In terms of travel time, it's about 9 months in either direction; similar to some early sea travel.
Deimos's surface gravity is very, very weak. A man could jump off of the planet and go into an independent orbit around Mars; it's only about 20 km/h.
Finally, Deimos is believed by some scientists to contain ice. If so, mining this ice and using it for fuel could well open up space all the way from LEO to Mars and on to the main belt asteroids; rockets that are only currently able to reach LEO would be able to refuel there; perhaps even Jupiter and Saturn may be in reach. Certainly if the fuel is there returning it to LEO can be done cost effectively.