Rimae Sirsalis


Avani Soares

Parsec Observatory, Canoas, Brazil

C14 Edge + ASI 290 + IR Pass 685

Rimae Sirsalis
Judging by what is being read on the internet recently, there is a lot of confusion and a big disagreement about the channels, or lunar grooves. Different sites say that Rimae Sirsalis or Sirsalis Rille, shown in the attached images, is a lava tube or a lava channel, but some admit a certain confusion since this volcanic feature was formed in the highlands of the Moon instead of forming in the seas. The word rille (channel or groove) is used to describe a wide variety of valleys that are considerably longer than broad. Sinuous channels, like the Marius, are volcanic lava tubes. Linear, such as the Ariadaeus and the concentric ones like the Hippalus are tectonic cracks usually associated with the tension regime related to the impact basins.

The linear channels are interpreted as depressions formed on vertical magma bundles called dikes. Dykes are born in regions where the horizontal tension is extensional, making it easy for the dike to push up the surrounding rocks. Sirsalis Rille, is one of the largest channels, or linear grooves of the Moon, approximately 380 km long. According to bibliographical references, the channel has a maximum width of 3.7 km and an average depth of 230 meters. What supports the interpretation of this channel as a volcanic dam, are the magnetic measurements made by the Apollo and Lunar Prospector ships, which revealed a large linear anomaly on the dam. Sirsalis Rille is between 8 or 10 channels approximately radial to the hypothetical Gargantua impact basin that had its west third filled by the Oceanus Procellarum. Somehow the levees are related to the vast Gargantua depression, but exactly how this relationship occurs is still a mystery.

The Sirsalis Channel is fascinating because in addition to being large in length it has a strong gravitational field, but the channel observed in the images can also be considered remarkable as it falls inside the De Vico A crater and then climbs its wall continuing on the other side. Looking like this, it seems that he appeared in the region like lightning. But it came about thanks to forces coming from below, apparently a vertical sheet of magma that also probably traveled sideways and fed the lava to the Oceanus Procellarum. As the channel can not float it is lower inside the crater than in its ring. The canal then crosses the interior of a large unnamed crater where it undergoes a great diversion. The reason for this deviation is quite mysterious, but one thing that is clear is a series of channels that seem to start at the Sirsalis and head for Darwin, where a strong channel crosses the interior diagonally. The channels sometimes seem to have a life of their own doing what they want to do. At least that’s how they seem to be when we can not understand the forces that created them.
Both photos were taken at intervals of 11 minutes and rotating the camera in the eyepiece to create two apparently different images.

Source: LPOD / Cienctec / Rubens Nucleus of Moon Studies
Adaptation and text: Avani Soares