Geiger is a
lunar impact crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact crater ...
on the
far side of the
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...
. It lies to the southwest of the much larger walled plain
Keeler, and slightly farther to the northeast of the huge walled plain
Gagarin
Yuri Alekseyevich Gagarin; Gagarin's first name is sometimes transliterated as ''Yuriy'', ''Youri'', or ''Yury''. (9 March 1934 – 27 March 1968) was a Soviet pilot and cosmonaut who became the first human to journey into outer space. Tr ...
. To the south is the crater
Cyrano.
This is a not-quite symmetrical crater formation with small outward bulges along the north and northeast. The rim to the southeast is less well-formed than elsewhere. The northern inner wall is more extensive than elsewhere, slumping across about one-third the inner floor. The interior is otherwise relatively level and is marked 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 midpoint that is closest to Geiger.
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Impact craters on the Moon