열람 Rimae Sirsalis
Rimae Sirsalis is a lunar rille, an open lava channel or a collapsed lava tube on the Moon. It is located at 15.7°S 61.7°W and is 426 km long.
Rimae Sirsalis is in an unusual location for a rille. Most rilles are near the edge of maria, or inside them. Rimae Sirsalis cuts across highlands almost exclusively, and seems to go in places where such a formation would be impossible. It starts at the edge of Oceanus Procellarum near the modest crater Sirsalis from which it gets its name and proceeds directly away from the mare, eventually ending up among the cracks in the floor of the crater Darwin. Along the way it passes through craters, ranges of hills, and other small rilles.
It is unclear how exactly a lava flow would have followed such a path, and various theories have been presented for its formation. One popular theory is tectonic activity, making Rimae Sirsalis a fault. However, it is not thought that there was much tectonic activity on the Moon at the time when the feature is likely to have formed. Another theory is that the groove is a collapsed dike of some sort. Dikes are igneous intrusions into weak rock, solidified lava that squeezed into a weak seam. This theory is not particularly well supported either.
Rimae Sirsalis has another unusual feature, a strong localized magnetic field. The Moon’s overall magnetic field is very weak in the present day, but it is thought that about 3.8 billion years ago the Moon may have had a global magnetic field as strong as that of Earth. Rimae Sirsalis may represent “fossil” magnetism from that era.