Rimae Sirsalis is 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...

 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...

. It is located at and is 426 km long. It was formed by extension of the surface, possibly due to dike propagation in the subsurface.

Rimae Sirsalis cuts across highlands almost exclusively. It starts at the edge of Oceanus Procellarum

Oceanus Procellarum

Oceanus Procellarum is a vast lunar mare on the western edge of the near side of the Earth's Moon. Its name derives from the old superstition that its appearance during the second quarter heralded bad weather...

 near the modest crater Sirsalis

Sirsalis (crater)

Sirsalis is a relatively young lunar impact crater located near the western lunar limb, to the southwest of the Oceanus Procellarum. The crater lies across a ridge that runs in a north–south direction. It has a sharp edge and a low central peak...

 from which it gets its name and proceeds directly away from the 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...

, eventually ending up among the cracks in the floor of the crater Darwin

Darwin (lunar crater)

Darwin is a lunar crater of the type categorised as a walled plain. It lies in the southeastern part of the Moon, and is sufficiently close to the limb to appear significantly foreshortened when viewed from the Earth. Attached to its southern rim is Lamarck...

. Along the way it passes through 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...

s, ranges of hills, and other small rilles.