Sometimes you just need to 'vent'

Low reflectance material cascaded down the wall of what is likely a volcanic vent in the southwestern portion of the Orientale basin. Image field of view approximately 750 meters, from LROC NAC observation M1150135366,  LROC orbit 21493, March 22, 2014; incidence 37.45° resolution 77 cm from 75.55 km over 30.12°S, 262.19° [NASA/GSFC/Arizona State University].

H. Meyer
LROC News System

Pyroclastic deposits on the Moon are often identified by a mantled appearance and low reflectance. These deposits are the result of an explosive eruption (or many) that involved a volatile component, likely carbon monoxide. The resulting fine-grained debris, including glass beads like those sampled by Apollo 17, gives the surface a dark, mantled appearance (See WAC image below).

So, where did the low reflectance material come from? The low reflectance material here flowed down the wall of a kidney-shaped (reniform) depression located at the center of the annulus.

Expanded 3.8 km-wide context for LROC Featured Image released April 15, 2014 - outlined box - northwestern rim of pyroclastic vent, southern frontier Mare Orientale impact basin. Mosaic of left and right frames of LROC NAC observation M1150135366  [NASA/GSFC/Arizona State University].

The lack of a discernible crater rim and irregular shape make this depression a suspect (See WAC image below). The walls of the depression are steep-sloped, yet the floor is fairly flat, which is best observed in a color-shaded digital terrain model (DTM). Such reniform depressions are observed in other locations across the Moon, such as Sulpicius Gallus, interpreted to be a pyroclastic source vent.

A higher angle of incidence, in this 2.8 x 7.5 km-wide field of view, washes out much of the finer grain albedo, though a look at the larger 40 percent -3760 x 9920- reproduction does reveal much of the detail of the rim, walls, boulder trails and debris-filled floor of the two-kilometer deep "smoke ring vent."  The area of interest on the upper right, also in the LROC Featured Image can be compared. LROC NAC mosaic of the left and right frames of observation M1099502843, LRO orbit 14378, August 13, 2012; illumination incidence angle 45° at 76 cm per pixel resolution, from 72.13 km over 30.11°S, 261.81°E [NASA/GSFC/Arizona State University].

If the kidney-shaped depression is the source of the low reflectance material, it is likely that material was ejected from the source vent at high velocity, creating an umbrella-shaped plume and depositing the dark, fine-grained material in a ring around the vent.

The larger than lunar average - 12.5 x 19.75 km pyroclastic "smoke ring vent," on the southwestern frontier of the Mare Orientale impact basin, is also hub to a regionally distinct 190 km-in diameter ring of darker material that, while not apparent in topographic studies, stands out in all native reflectance photography. Medium resolution Chang'e-2 Global albedo Mosaic [CNSA/CLEP].

Pyroclastic deposits are currently of interest to lunar scientists as a possible resource for future missions to the Moon. Such deposits are rich in hydrogen and helium-3, two potential resources for energy production, and iron and titanium, which have engineering applications.

Elevation study, LROC WAC-derived GLD100 topography in color-coded overlay onto LROC global normalized reflectance data. The high mountains of the concentric Orientale impact basin ring, where the vent is nested, offers a high vantage. Elevations range over 4000 meters in 10 km [NASA/GSFC/Arizona State University].

LROC WAC normalized reflectance 643 nm, of the low-reflectance pyroclastic annulus on the southwest Orientale impact basin. The annulus is approximately 180 km in diameter [NASA/GSFC/Arizona State University].

The necessary capabilities for utilizing resources such as these in-situ, or on site, are currently under development. In-situ resource utilization (ISRU) is critical to the future of exploration of areas that would otherwise be beyond our reach, both physically and financially.

Another opportunity to display this stacked three-color image of the Moon's western hemisphere, which features Mare Orientale so prominently and demonstrates that the pyroclastic annulus south-southwest of its central plain, is large and prominent enough to be photographed from more than half a million kilometers away. In this case, captured by the Jovian probe Galileo at 1735 UT, December 9, 1990 [NASA/JPL].

Do some investigating of your own with the full NAC, HERE.

Related Posts:
Pyroclastics and an unnamed Procellarum vent
Source vent for Rima Prinz I
Craters on the Schrödinger pyroclastic cone
Morphology and distribution of volcanic vents in the Orientale basin from Chandrayaan-1
Unassuming volcanic vent north of Aristarchus Plateau
New pyroclastic structures identified using LROC data
A dark cascade at Sulpicius Gallus
Hyginus and pyroclastics
Layer of pyroclastics in Sinus Aestuum
Lavoisier Pyroclastics
Pyroclastic Excavation
Pyroclastic Trails
Pyroclastic Vent at Orientale DTM