Earthshine

A striking young Moon, only 2.35 days past New, only 5.5 percent illuminated by the Sun, the remainder in earthshine, brought out with exceptional artful detail. The target was 399,215 km away and slowing as its approaches perigee at roughly a kilometers per minute [Maurice Collins/Moon Science].

New oblique views of Gruithuisen Domes

An oblique view of the northern portion of the Gruithuisen Gamma volcanic dome, from the northwest. From a new LROC Narrow Angle Camera (NAC) mosaic M1106087898LR, LRO orbit 15300, October 28, 2012; overall resolution 4.9 meters per pixel [NASA/GSFC/Arizona State University].

Sarah Braden
LROC News System

The last LROC Featured Image post on the Gruithuisen Domes featured some of the earliest Narrow Angle Camera (NAC) coverage of this amazing region.

Now LROC brings you an even more dramatic view of these volcanic domes from an oblique angle (viewing from East to West), from an altitude of 154 km (96 miles) above the lunar surface.

Located along the mare/highlands boundary, on the northeast border of Oceanus Procellarum (36.6°N, 319.9°E), the three Gruithuisen domes Gamma, Delta, and Northwest (NW) are primary examples of lunar silicic volcanism.

A thumbnail image of the 20376 x 6728 oblique NAC montage users can zoom into HERE. The crater Gruithuisen B is 9 km in diameter (north is to the right) [NASA/GSFC/Arizona State University].

Field of view seen at an oblique angle sketched out (arrows) on a photometric work-up of an LROC monochrome Wide Angle Camera (WAC) overview by Maurice Collins, originally presented as a Lunar Picture of the Day (LPOD), September 27, 2010 [NASA/GSFC/Arizona State University].

Silicic volcanism is relatively rare on the Moon. The Gruithuisen Domes pre-date the lunar mare in this region, so some portion of these domes has been covered by mare basalt, although there are also contacts with the older highlands material. Silicic volcanism might have been more widespread during the Moon's early history, however, any evidence for that may be buried beneath the maria. We know that the composition of the Gruithuisen Domes are different from that of the mare and the highlands from Earth-based telescopes, Lunar Prospector gamma-ray spectroscopy data, and Clementine multispectral data. The Gruithuisen Domes are characterized by relatively high reflectance and strong absorptions in the visible and ultraviolet. The Domes are also low in iron and titanium abundance compared to the lunar maria. New data from the Diviner instrument on the LRO spacecraft confirmed that the Gruithuisen Domes are silicic.

Colorized topography of the Gruithuisen Domes region derived from the 100 m/pixel LROC WAC DTM. Contour line interval is 220 meters [NASA/GSFC/Arizona State University].

Experience the full resolution oblique image HERE.

Related LROC Featured Images:

Gruithuisen Domes - Constellation Region of Interest
Morphology of lunar volcanic domes
LROC NAC DTM Viewer Gruithuisen Domes (ROI) 1 - 2 - 3 - 4 - 5
Hansteen alpha yields some of its secrets
Silicic volcanism on the Moon
Compton Belkovich - Constellation ROI
Hortensius Domes - Constellation ROI

LROC: Inside Rima Hyginus

Collapse features within Hyginus Crater. 1240 meter-wide field of view from LROC Narrow Angle Camera (NAC) observation M104476560L, LRO orbit 556, August 9, 2009; resolution 1.24 meters from 122.77 kilometers. View the LROC Featured Image, released June 12, 2012 HERE [NASA/GSFC/Arizona State Univeristy].

Sarah Braden
LROC News System

Most craters posted to the LROC Featured Image page are impact craters, however, Hyginus Crater (located at 7.75°N, 6.27°E, in Sinus Medii) is a volcanic crater known as a caldera. Two main pieces of evidence suggest that Hyginus Crater formed through volcanic processes. First, Hyginus lacks a raised rim typical of impact craters. Second, the rim of Hyginus is irregular (not circular), which is typical for volcanic craters caused by collapse. Also, if you look closely with the LROC NAC, the interior of Hyginus has a number of small irregular depressions which are most likely collapse features, indicating a volcanic origin for Hyginus. These irregular depressions are in the Featured Image, distinguished by rough, high reflectance material around their edges.

Eight meter per pixel resolution view from LROC QuickMap shows the "meniscus hollows" features in context with the eastern interior of Hyginus [NASA/GSFC/Arizona State University].

The entire Hyginus region, shown in the LROC context image below, is a complex piece of lunar real estate. Not only do you have the volcanic crater Hyginus, but also Rima Hyginus, a linear rille, more volcanic collapse craters aligned with the linear rille, and a pyroclastic deposit around the crater Hyginus. How do all the geologic features relate to one another? The Hyginus region is so amazing that it was a candidate landing site for the canceled Apollo 19 mission. Had events turned out differently, we might know much more about the pyroclastic materials and the Hyginus caldera. Continue reading below for a summary of the scientific theory of how the Hyginus region formed.

An almost oblique view (spacecraft and camera slewed 19.57° east from nadir), LROC WAC view from 42.29 kilometers over an area west of Rima Hyginus. The caldera, particularly its east walls, can be seen here in some relief, without the high angle of incidence seen in the next image. LROC WAC observation M165814883C (604nm), LRO orbit 9570, July 20, 2011; native resolution 62.94 meters [NASA/GSFC/Arizona State University].

In a recent paper, scientists proposed a model of formation for Hyginus crater and Rima Hyginus. First, a body of magma from the mantle rose vertically through the lunar crust. The magma stopped rising near the surface and spread out laterally. This introduction of new material beneath the surface caused stress on the crust, which resulted in faulting. Eventually, gasses from the magmatic material still underneath the surface built up and increased the gas pressure, further increasing the stress on the crust.

LROC Wide Angle Camera (WAC) monochrome (689nm) observation of the Hyginus region. The yellow arrow marks the location of the collapse feature, the meniscus hollow, within Hyginus caldera seen at high resolution in the LROC Featured Image and the white arrow designates a small dome feature brought to attention by Maurice Collins. LROC WAC M117447052ME, orbit 2442, January 6, 2010; incidence angle 81.75° and a 62.6 meter resolution from 41.63 kilometers [NASA/GSFC/Arizona State University].

This stress eventually caused graben to open along the faults, and the same release of stress initiated an eruption, including pyroclastic materials. After the eruption of magmatic material an empty cavity beneath the surface was left behind. This cavity collapsed, creating Hyginus crater. The collapse craters along the linear rille also formed in a similar way.

LROC NAC image M126887222L gives another look at the largest collapse feature in the main image. This image field of view is 487 meters wide (588 meters in the LROC Featured Image release), and has a lower illumination incidence angle, which emphasizes albedo differences over the kind of relief visible in the LROC WAC image immediately above. LRO orbit 3833, April 26, 2010; incidence angle 28.28° with a resolution of 0.48 meters from 40.55 kilometers [NASA/GSFC/Arizona State University].

Explore more of the Hyginus caldera in the full LROC NAC, HERE.

Related Posts:
LPOD: Another Ina?

Ina of the Meniscus Hollows

Whale of a hollow

It's a gas, man
Brayley G
Sinuous Chain of Depressions
It's the Moon's Fault

You can read more about the Hyginus region in the Icarus paper, "An igneous origin for Rima Hyginus and Hyginus crater on the Moon."

The central and western Hyginus and Rima Hyginus region and points immediately north and beyond under mid-morning illumination, as seen from around 100 kilometers over the south , a forward-looking HDTV still captured by Japan's lunar orbiter SELENE-1 (Kaguya) in 2008 [JAXA/NHK/SELENE].

Support a startling and new 3D Moon map

Help "Kickstart" the wide distribution and availability of this excellent piece of work, a 3D map of the Moon that represents a substantial improvement over the famous (and incomplete) National Geographic lunar map first sent to Society members in March 1970.

Lunar observers who devote much time online are already aware of the existence of a new anaglyph 3D Moon map because of the efforts of Dave Mosher for Wired via Charles A. Wood's essential "Lunar Picture of the Day."

As Chuck wrote very early February 11, "The Wired Science website just featured this stereo image of the Tycho ... region of the Moon.

"Jeffrey Ambroziak created the 3-D image from LRO digital terrain data by constructing red and blue anaglyph images from two slightly different perspectives. He and his father patented a new technique to create stereo images that work when viewed from nearly any angle or distance.

"As I have mentioned before, I can't see stereo so get out your red-blue glasses and send me your comments on how it works. Is it better than LRO anaglyph images by Maurice Collins and others?"

Echoing Dave Mosher's comments for Wired, this is a remarkable and very useful piece of work set up in such a way that everyone can both contribute and benefit.

View Dave Mosher's report on the Ambroziak 3D map HERE.