Rough Around the Edges

Rimma Suess
With peppered flanks, Rima Suess wanders over 150 km through Oceanus Procellarum. The rocks that rest on the walls of this lunar rille are perhaps remnants of much larger boulders that have eroded down to meter sized rocks due to micro and macro meterorite bombardmet. LROC NAC image M168516400R has a width of ~400 m, and North points up [NASA/GSFC/Arizona State University].

Rima Suess (7.81°N,-47.59°E), located in Oceanus Procellarum, is a long, meandering narrow depression called a sinuous rille. Sinuous rilles, most commonly found in mare surfaces, are thought to have been carved by hot rivers of lava, which thermally and mechanically eroded the channels we see today. About 3.5 billion years ago the Moon was much more volcanically active, pouring vast amounts of lava onto the surface. The large dark mare regions of the Moon were formed by massive eruptions of iron rich basaltic lava during this time.

The boulders along the walls of the rille probably were a coherent mass when the lava flows cooled, breaking up over billions of years of impacts into the boulders we see today. Gravity then pulled this material down the slope of the rille; this process is known as mass wasting. We see rock outcrops over the entire path of Rima Suess in the LROC NAC image M168516400R.

LROC WAC context image of Rima Suess
LROC WAC context image of a portion of Oceanus Procellarum. Rima Suess winds from the bottom of the image North, then diagonally across the top of the image WNW. The red solid rectange depicts the footprint of the NAC from which today's Featured Image was derived from, and the dashed arrow points to the approximate location of the Featured Image; the width of this image is ~70 km [NASA/GSFC/Arizona State University].

Lunar rilles are exciting places for lunar scientists because they may cut through and expose the different layers of lava flows in the maria.  This gives scientists insight into the volcanic processes present during mare formation, and how they evolved with time. Explore the winding path of this portion of Rima Seuss in the full resolution LROC NAC below:


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Published by Raquel Nuno on 5 June 2014