The Pipette rille where Reiner Gamma begins

Figure 1. LROC NAC mosaic M1123960471RL, LRO orbit 17613, May 13, 2013; camera and spacecraft slew -10.3° off nadir, angle of incidence 71.95° over an 11.5 km-wide field of view resolved at 1.2 meters per pixel from 117.54 km over 11.76°N, 304.54°E [NASA/GSFC/Arizona State University].

Joel Raupe
Lunar Pioneer

Our on-going LRO-aided Marius Hills Survey has been on the lookout for just this sort of LROC NAC observation, one offering a low (high) angle topographic view of the "pipette" and the approximately 5-km square area on the southwestern frontier of that shield volcano dome field in Oceanus Procellarum where the prominent Reiner Gamma swirl albedo and magnetic anomaly begins it 550 km meandering journey to the south-southwest.

Figure 2. As context, an animated image juxtaposing four LROC Wide Angle Camera (WAC) views of a roughly 5600 square kilometer (62 x 88 km) region surrounding the northeast terminus of the Reiner Gamma albedo swirl where it emerges from the Marius Hills shield. Beginning after sunrise, when long shadows emphasize elevation the animation slides through mid-morning, and early through late afternoon lighting angles. Under high Sun topography gives way to raw surface reflectivity and Reiner Gamma's meandering becomes clearly visible [NASA/GSFC/Arizona State University].

Though the narrow dusting of the continuous swirl feature is not readily visible in the image above, from orbit 17613, it can easily be seen in close-up observations of this same ground in earlier NAC mosaics captured under a high (low-angle) Sun and in orbital photographs at least as far back as Lunar Orbiter IV (IV-152-H2).

Figure 3. Junction, or "contact," where the Reiner Gamma swirl albedo anomaly (with its attendant crustal magnetic field) meets the Marius Hills dome field, a shield volcano in Oceanus Procellarum. The yellow rectangle outlines the field of view captured at high-resolution in figure 1 (LROC NAC mosaic M1123960471RL). Photograph frame from Lunar Orbiter IV photograph 157 (IV-157-H2), May 1967, from 2670 km over 13.91°N, 305.83°E [NASA/JPL/LPI].

We will be posting this image there, along with associated links, later today, September 20, 2013. Image part of the 15th LROC release to the Planetary Data System, last weekend.

There's an additional Lunar Orbiter perspective useful for adding to one's understanding of Reiner Gamma's superficial relationship, probably indicating a buried deeper interrelationship, an oblique image capture by Lunar Orbiter II, the medium resolution frame from observation 215 (II-215-M). A close comparison of that image with the animation of LROC WAC images (figure 2) seems to show the Reiner Gamma albedo swirl does not "meander" in and around all the domes in its path, like water flowing around rocks in a river. Some of the intermediate vent domes seem to have had their highest surfaces painted with the same brush.

Related Posts:
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Rima Marius Layering (June 27, 2013)
The Moon's antipodal magnetism mystery (June 19, 2013)
LRO team delivers 12 quarterly release to PDS (December 16, 2012)
LRO Release 11 to the Planetary Data System (September 27, 2012)
Bubble, bubble - Swirl and Trouble (July 19, 2012)
The new Kaguya Terrain Camera tours (May 5, 2012)
LROC 9th PDS Release (March 15, 2012)
LROC releases 57 NAC elevation models (February 6, 2012)
Magnetic Moon (October 19, 2011)
LROC Quickmap improvements dazzle (October 17, 2011)
Moon in UV sheds light on maturation and materials (October 12, 2011)
Volcanic Shields of the Moon (March 21, 2011)
Morphology of lunar volcanic domes (February 22, 2011)
The largest volcano on the Moon (October 19, 2010)
Grand lunar swirls yielding to LRO Mini-RF (October 4, 2010)
Another look at Reiner Gamma (June 30, 2010)
Marius Hills Constellation Region-on-Interest (June 2, 2010)
Hearts of Marius, Shadows of Yutu (May 29, 2010)
Local Topography and Reiner Gamma (May 22, 2010
Lunar Swirl phenomena from LRO (May 17, 2010)
LRO-LROC-LOLA: Marius Hills (March 20, 2010)