Gärtner is the 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...

-flooded remnant of a 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...

 in the northeast part 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 is located on the northern edge of the Mare Frigoris

Mare Frigoris

Mare Frigoris is a lunar mare located just north of Mare Imbrium, and stretches east to north of Mare Serenitatis. The mare is in the outer rings of the Procellarum basin...

. The southern half of the formation is completely missing, and Gärtner forms a semi-circular basin along the edges of the lunar mare

Lunar mare

The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and...

. To the north lies the crater Democritus

Democritus (crater)

Democritus is a lunar impact crater that is located on the northern part of the Moon, just to the north of the Mare Frigoris. Just to the south of Democritus is the lava-flooded crater Gärtner, which forms a bay on the mare. Directly to the north is Arnold, another flooded formation.The rim of...

.

The surviving parts of the crater rim are heavily worn and eroded, with notches and indentations formed by past impacts. The floor has a few low rises in the northern half. A rille

Rille

Rille is typically used to describe any of the long, narrow depressions in the lunar surface that resemble channels. Typically a rille can be up to several kilometers wide and hundreds of kilometers in length...

designated Rima Gärtner runs from the mid-point of the crater toward the northeast rim, for a total length of about 30 kilometers. The bowl-shaped craterlet Gärtner D is located near the mid-point between the two ends of the crater rim.

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 Gärtner.

Gärtner	Latitude	Longitude	Diameter
A	60.7° N	37.8° E	14 km
C	59.4° N	31.0° E	8 km
D	58.5° N	33.9° E	8 km
E	61.5° N	43.8° E	7 km
F	57.5° N	30.1° E	14 km
G	59.5° N	39.8° E	33 km
M	55.5° N	37.0° E	11 km