Archive | October 2012

A beautiful ray crater on the far side

This week we’re featuring yet another crater posted by Moon Zoo user kodemunkey, this one is on the far side near crater Lents Lenz and has a wonderful white texture around the central impact area. It also has some areas of “black stuff” around the edge of the crater. We have a “black stuff” project on the Moon Zoo forum here: TLP Project – Black Stuff


from NAC strip: M186541565RC
Latitude: 3.3, Longitude: -100.3


Black stuff on the northern edge of the crater.


Detail of debris flow down the crater wall.

This unnamed crater is mentioned in this article where it is called the most beautiful raycrater of the entire moon’s surface.

See LPOD lunar photo of the day, 12 December 2007 for a great image of the crater.

Up and Down the Marius Hills

Looking a little like a lunar air base complete with landing strips this patch of rugged terrain was posted on the forum by kodemunkey who came across it on one of his regular visits to the Marius hills region of Oceanus Procellarum. It’s difficult to see what’s going on without looking at the wider picture. Below are 2 views of the immediate surroundings under different illumination angles. It’s a good example of how the appearance of the lunar landscape changes under different sun angles. The pale tracks in the first image appear black in the second and only by examining both images can we get a full picture of the surrounding terrain. Click on the NAC references to explore the area in more detail. Note the NACs are rotated 1800 and the following images are corrected for north up.
Incidence angle 75.3
NACs M193289571LE and M193289571RE
Incidence angle 36.2
NACs M183861185LE and M183861185RE

14.3N -50.6W

An even wider view places the feature north west of Marius R crater in an area where the outer rays from Aristarchus, Kepler and several craters to the west overlap on the eastern edge of the Marius hills. This particularly rugged terrain is also marked by lava flows, sinuous rilles and mare ridges. About half of the Moon’s volcanic domes are in this region. Lunar domes are much smaller than shield volcanoes on Earth. The Marius hills range from 200-500m in height whereas the Mauna Loa volcano in Hawaii (the largest shield volcano on Earth) is 17,170m tall. Here is a wide field image with the featured region indicated showing its proximity to the Marius domes:


image from Global Morphologic Map

Photographed from a more oblique angle by the LRO’s Wide Angle Camera the domes are more impressive:


from LPOD 

So what is going on in kodemunkey’s image? Rotating the image so that north is up and using the topography graph from the ACT-REACT Quick Map shows a steep drop from west to east. Lava flows appear to have created a complex knot of ridges and valleys. The pale tracks at top left are very bouldery and connect to 2 small craters suggesting that they are more recent landslides and flow from higher ground towards the lower rugged region.


bigger image

Kodemunkey found his image from the latest LRO data release 11.

Resources:
ACT-REACT Quick Map link
Paper: Compositional variability of the Marius Hills volcanic complex from the Moon Mineralogy Mapper (M3)

Exploring the Marius Hills Region

Moon Zoo user kodemunkey posted a great image of a fresh white crater with garcinia residue in the Interesting terrain thread on the 29th September 2012.


NAC Strip: M170877942RE Latitude: 9.4 Longitude: -48.3 (close to Marius V crater)

After finding the fresh white crater on the NAC strip I did a bit more exploring and found a crater with a good example of “black stuff” – see the TLP Project – Black Stuff for more information.


“Black Stuff” – same NAC strip as above.

The Marius Hills region of the Moon is full of interesting formations and contains many volcanic domes, cones and rilles, and is well worth exploring.

I looked at a wider view of the area using the ACT-REACT tool and discovered the Rima Suess rille which runs for about 200 km across this region. There is a strange elongated “craterlet” to the north-west of the rille which appears to be connected to it in some way. I can’t find much information about this craterlet and it would be interesting to know how it formed and if it is related to the Rima Suess at all.


from ACT-REACT tool. Craterlet is at Latitude: 8.65 Longitude: -48.66

Herodotus Omega

In Oceanus Procellarum in between Marius and Herodotus craters lies Herodotus Omega volcanic dome. This region contains a number of volcanic features, such as sinuous rilles and the Marius hills volcanic domes further south. Herodotus Omega is an impressive mound with a 3.5 km long crater or collapsed lava tube on the summit. With the Sun high overhead, however, it’s easy to overlook it.

High sun

Lat: 20.8   Lon: -50.0
Forum regular JFincannon has a knack of finding interesting images and came across the above feature while browsing a Wide Angle Camera (WAC) image of a region around Aristarchus. He then persevered to find the same region imaged under a lower Sun. It was well worth it to see the dome and a nearby rille pop out into view.

Low sun

It is described as a “Platykurtic oblong mare dome with trench-like crater or collapsed lava tube on summit.” in the GLR Catalog of Lunar Domes and also appears in an unofficial Brungart catalogue identified by LPOD creator Chuck Wood.

This is a cross-section from the Quick Map tool showing the shape and height of the mound and depth of the central depression.

Though striking in LRO images there are many volcanic domes in this region and this is just one more so perhaps not surprisingly a search of the literature revealed no recent papers referencing Herodotus Omega. JFincannon found these papers from over 30 years ago. Herodotus Omega warrants only the briefest of mentions:

So it’s overdue some time in the limelight. You can explore further via the Narrow Angle Camera (NAC) images: M137875459RE, M116642442RE and the ACT-REACT Quick Map.  To fully appreciate the dome you really need to explore the wide-field WAC images. This is how JFincannon did it:

1. He searched for low Sun angle WAC images of Aristarchus (incidence angle of 70-90 degrees) using the WMS browser.
2. Then he used Mosher’s LROC WAC Previewer.
3. Full instructions are here.