Cartan is a small lunar

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 near the eastern edge of the Moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

. It lies just to the west of the larger Apollonius

Apollonius (crater)

Apollonius is a lunar crater located near the eastern limb of the Moon. It lies in the region of uplands to the west of Mare Undarum and northeast of the Sinus Successus on the Mare Fecunditatis...

. The rim is circular with a tiny crater along the eastern side. The interior floor is about half the diameter of the crater. A smaller crater attached to the southern rim is also attached to the north rim of Apollonius H, forming a short crater chain.

Cartan was designated Apollonius D before being named by the IAU

International Astronomical Union

The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

.