Lunar Reconnaissance Orbiter Camera

A Tortuous Path in Posidonius

Slope Map of Sinuous Rille in Posidonius
This may look like a work of abstract art, but in reality, it's for science! This colorful image is an LROC slope map of the northwestern portion of the floor of Posidonius crater. Warmer colors indicate steeper slopes, whereas cooler colors are shallower slopes. A rille winds its way across the floor and flows along a southerly course, diverging from its path along the crater rim. A tributary rille can be seen joining the main rille at the bottom center. Image width is approximately 5.5 km. North is up [NASA/GSFC/Arizona State University].


Sinuous rilles, such as the one above, form through the flow of hot, turbulent lava. Rilles can be found in many locations across the lunar surface and two very different mechanisms are generally thought to form them. Mechanical erosion refers to the physical removal of material by the lava flow, similar to how rivers erode channels on Earth. Alternately, some lavas are so hot that they partially melt the substrate, and deepen the channel through time. These processes on there own would both result in downcutting into the surface, but they were often simultaneously working to reshape the lunar surface. Posidonius exhibits several rilles of differing types, seen below (linear and sinuous).

WAC Context Image of Posidonius
LROC WAC context image of Posidonius (95 km). The sinuous rille from Today's Featured Image (yellow box) made its way south across the smooth mare plains of Posidonius. Notice that the crater rim is breached where the sinuous rille meets the wall on the left side of the image. Image width is approximately 145 km [NASA/GSFC/Arizona State University].

Posidonius is a 95 km diameter crater on the northeastern margin of Mare Serenitatis. The floor of Posidonius exhibits a number of interesting geologic features. In the western portion of the floor, the sinuous rille from Today’s Featured Image winds its way through smooth plains that partially bury the crater wall. In the eastern portion, the floor is fractured and tilted, similar to craters like Karpinskiy, creating a cliff that drops ~ 1 km to the smooth floor. When compared to the highlands, Posidonius has few craters superposed on its floor, like Posidonius A (11 km) & C (3.5 km), indicating that the floor of this crater is younger.

Check out the full slope map below!

Download your own version here!

Related Posts:

Rimae Posidonius

Posidonius Y

Meanders in Posidonius

NAC DTM Posidonius

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