Petrov is an impact 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...

 along the southeastern limb 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...

. The crater is difficult to observe in this location, and visibility of this feature is affected by libration

Libration

In astronomy, libration is an oscillating motion of orbiting bodies relative to each other, notably including the motion of the Moon relative to Earth, or of Trojan asteroids relative to planets.-Lunar libration:...

. The nearest crater of note is Chamberlin

Chamberlin (lunar crater)

Chamberlin is a lunar crater that is located on the far side of the Moon, just past the southeastern limb. It lies to the southeast of the crater Jeans, and Moulton is attached to the southeastern rim of Chamberlin...

, just on the far side to the northeast. Somewhat farther to the west-southwest of Petrov is Gill

Gill (lunar crater)

Gill is a lunar crater that is located near the southeastern limb of the Moon. Due to its proximity to the edge of the Moon as seen from the Earth, this crater is viewed nearly from the side and it can become hidden from sight due to libration. The crater lies to the southwest of the irregular Mare...

.

The rim of this crater has been worn and eroded by impacts, leaving an irregular ring of ridges and incisions along the inner wall. The smaller crater Petrov A intrudes slightly into the southern rim. Along the southeast, Petrov B is attached to the southeastern exterior and the two are joined by a narrow valley.

The interior floor of Petrov has been completely resurfaced by basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

ic lava

Lava

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

, leaving a low-albedo

Albedo

Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...

 surface that is relatively smooth and featureless. This material is nearly as dark as the Mare Australe

Mare Australe

Mare Australe is a lunar mare located in the southeastern hemisphere of the Moon. It is 603 kilometers in diameter, overlapping the near and far sides of the Moon. Smooth, dark volcanic basalt lines the bottom of the mare...

to the north. The floor is marked only by a few tiny craterlets.

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater mid-point that is closest to Petrov.

Petrov	Latitude	Longitude	Diameter
A	62.5° S	88.3° E	17 km
B	62.3° S	90.5° E	31 km