Balmer 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 remains of a 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...

. Only the heavily worn southern and eastern sections of the crater still survive; the remainder being overlaid by a 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...

 flow that joins to the nearby 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...

. Balmer lies to the east-southeast of the crater Vendelinus

Vendelinus (crater)

Vendelinus is an ancient lunar impact crater located on the eastern edge of Mare Fecunditatis. To the north of Vendelinus is the prominent crater Langrenus, while to the southeast is Petavius, forming a chain of prominent craters near the eastern 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 Balmer.

Balmer	Latitude	Longitude	Diameter
M	20.7° S	71.5° E	5 km
N	19.9° S	69.9° E	8 km
P	20.4° S	67.7° E	13 km
Q	18.7° S	70.5° E	7 km
R	18.7° S	69.1° E	4 km
S	18.4° S	67.6° E	6 km