Thursday, May 22, 2014

Kink in Rima Krieger

Rima Krieger winds its way through Oceanus Procellarum. Image width is ~ 3.5 km. Taken from LROC NAC observation M1152172510R, LRO orbit 21780, 50.29° incidence angle, resolution 1.35 meters, from 134.64 km over 29.19°N, 313.9°E [NASA/GSFC/Arizona State University].
H. Meyer
LROC News System

Rima Krieger is located in central eastern Oceanus Procellarum. "Rima", which means "fissure", refers to lunar rilles, a common feature on the lunar surface.

Rilles located in mare deposits can form by two mechanisms, channelized lava flow or lava tube collapse, often combined with tectonic stresses. They display three major morphologies: linear, arcuate, and sinuous.

Rima Krieger is a sinuous rille, meaning that its twists and turns resemble meandering rivers on Earth.  Sinuous rilles are thought to have formed as lava became channelized on top of a thick lava flow, as seen at Vallis Schröteri, or as lava flowed across the surface and carved into the substrate.

A roll through four modern orthographic perspectives of Krieger (with 10 km Van Bisbroeck crater superpositioned on its south rim) and the narrow pass through the crater's west wall, where Rima Krieger begins. The region is dominated by its proximity to young Aristarchus crater to the southwest. A 42 km field of view with data contributed by the Lunar Orbiter series, Clementine and LRO [NASA/GSFC/Arizona State University].
In the case of Rima Krieger, some of the meanders occur at nearly right angles, suggesting that the flow was controlled to some degree by underlying structure. These sharp turns appear just outside the rim of Krieger. It's possible that the lava flow was diverted by structure resulting from the impact itself.

LROC NAC mosaic M1145106645R, LRO orbit 20787, January 23, 2014; 48.1° incidence, resolution 1.34 meters from 134.41 km over 29.9°N, 313.87°E. The original, full-size reproduction of this mosaic can be viewed HERE [NASA/GSFC/Arizona State University].
The rille and impact in Today's Featured Image are only a few of the fascinating formations in this region. Rima Krieger is located in one of the most geologically diverse regions of the Moon. To its west, the Aristarchus Plateau stands above the surrounding mare. On the Aristarchus Plateau, we see mare basalts juxtaposed with anorthositic materials excavated by the Aristarchus impact and a dark mantle of pyroclastics over much of the plateau.

Telescopic mosaic from Earth at full Moon, stretched for color contrast, shows some of the wide variety of basalt in north Procellarum, and just how Krieger (arrow) overpowered by its young neighbor, bright Copernican age Aristarchus and its excavation of Aristarchus plateau.
Local evening view de-emphasizes albedo and emphasizes terrain relief in this telescopic look at a 630 km field of view from Krieger (arrow, north) and Marius. (note the Marius Hills as their low profiles come into view on their namesake's north-northwest. Even the long Marius sinuous rille can be seen winding through the plain just north of those Hills. Krieger's morphology is still dominated by Aristarchus. Late crescent Moon mosaic by Astronominsk, September 25, 2008.
Very reduced view of the full-size ASTRONOMINSK late crescent Moon mosaic of 22 images, showing the field of view immediately above in context (inset). Note the differing perspectives on the Aristarchus Plateau, seen from Earth under a high and low Sun due to libration. The full mosaic can be viewed at the ASTRONOMINSK website, HERE.
To the east of Rima Krieger, we cross the contact between Oceanus Procellarum and Mare Imbrium (passing many kipukas along the way) and run northeast into the Gruithuisen Domes. To the south, the Rimae Prinze Region displays its many sinuous rilles, flooded craters, and massifs. To explore the entire region in more detail, check it out through the LROC QuickMap, HERE.

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