Archive | October 2010

Lunar Gullies – slip sliding away….

Running water on Earth carves into soils causing gullies. These are particularly well seen on hillsides and steep slopes, often resembling ditches and small valleys. Similar features have been spotted on photographs of Mars (Fig. 1), but there is much scientific debate about whether such gullies are caused by running water, periodic release of snow or underground ice or frozen carbon dioxide or if they are formed in slope or debris collapses that do not have to involved water at all (e.g. landslides).

gullies on mars gullies on mars2

Fig. 1. Gullies on Mars.

In both cases the start of the gully is at the top of the image and material has flowed towards the bottom of the image. LEFT: Gullies in Nirgal Vallis. MGS MOC Release No. MOC2-535.This is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) narrow angle image of gullies carved into debris on the south-facing wall of Nirgal Vallis, an ancient martian valley.  Scaled image  width: ~3 km. RIGHT: MOC image S09-01005. Crater Wall in Noachis Terra. Scaled image  width: ~1 km. Here the gullies are well developed with deep upper cut regions and fan like debris deposits at the bottom of the slope.

In 2006 Gwen Bart, a US planetary scientist searched through available images of the Moon that were collected by 1960’s Lunar Orbiter mission to see if she could find examples of gullies on the Moon. She suggested that if gullies could be seen on the slopes of lunar craters, and as the Moon typically has very very little water, it may provide evidence that gullies on Mars don’t have to have formed in the presence of water or ice. Her preliminary results are presented here and there is a nice summary of the implications of her study here.

As Moon Zoo users well know – the new images by the LRO LROC NAC are knocking the spots off the older Moon photos! For example, now we have these amazing new NAC images they are showing that gullies really are found all over the Moon…

gambert c montage

Montage of LROC NAC image M127009259 (not map projected) showing view of Gambert C crater which is located on the nearside of the Moon near Copernicus crater.

gambertc 1 gambertc 2 gambertc 3

Close up images of gullies in Gambert C crater shown in wider view above. Several gully networks can be seen in each image. In all cases the source of the gullies is at the top of the image and they flow down towards the base on the image. Flows and gullies show lobate tracks and channels, often with blocky rubble material having been pushed to the sides and end of the main channel.

bright gully 1 bright gully 2

Left: Montage of LROC NAC image M105185599E (not map projected) and close up section shown at right. Bright, elongate gully tracks can been seen in the photo eminating from bright rubbley regions on the crater wall. The gullies start in the bottom left hand corner and flowed towards the top right.

See also the dramatic examples in Marius crater and look at the wide view of the area.

And Moon Zoo users have already done a great job in spotting some really nice examples of landslides, gullies and channels on slopes. Check out the examples in Birt crater, Proclus crater  and in other places on the Moon here and here.

So – we would like to issue a renewed challenge to keep a close eye out for gullies and landslides on the Moon. Hopefully your discoveries will help to provide a good database that scientists can use to address the diversity, shape and form of gullies on the Moon compared with those seen on Mars, the Earth and other planets.

Please remember, as well as posting examples on the Moon Zoo Forum under the landslides and gullies topic, if you find examples in the Moon Zoo user interface to flag these features as linear features so that we also have a record noted in our database!

Thanks for your help,

Katie
Moon Zoo Team

(Thanks to Allan Treiman and Amanda Nahm at LPI for drawing our attention to this interesting lunar science and Martian science topic).

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The Mystery at Milichius-A Crater

It started off as a normal enough Friday. I checked the Moon Zoo forum and did a little Boulder Wars. Then I received a PM from new forum member Astrospade with a link to a rather interesting picture s/he had found. I went to have a look and as the afternoon quietly slid towards the weekend the Moon Zoo community suddenly sprang into action.

Astrospade had noticed something interesting on a NAC image featured on the NASA mission site. The object in question is on NAC strip M102365048LE just to the right of Milichius A crater and it looked for all the world like a space probe.

This is the site Astrospade looked at with no mention of the “probe” in the main text. A couple of comments below the article are from people who had spotted the same feature but no-one got back to them and the comments feature now appear to be closed. Astrospade had also contacted the coordinator for the Lunar Reconnaissance Orbiter site but got no response.

I was intrigued enough to have a closer look. The blue rectangle on the small reference strip shows the position of the object.

An arrow points to a long thin shadow appearing to come from a tall structure next to a small white topped feature better seen in the enlarged section in the inset. With an incidence angle of 76.02 degrees all the surface features will cast very long shadows anyway but this particular long thin shadow looked different, very antenna-like and the white topped feature didn’t look very much like a rock! Unfortunately there are no further NAC images under different illumination to shed more light on the mystery ( :) ) and my observation request was denied as a similar request had already been submitted.

Milichius A is 10 degrees North and 30.2 West in Oceanus Procellarum region – just west of Kepler Crater.

The only thing we could find that came close was Luna 7 which crashed at 9.8°N 47.8°W. The difference in longitude amounts to around 546km. Was this too far for Luna 7 to scatter, bounce or spread? Could it even have broken up when hurtling towards the lunar surface with bits landing relatively softly away from the main crash site? Could the white object in the NAC image be the remains of the basket-like end of the Luna probe rather than a photographic artefact?

Luna 7
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Tom 128 took up the story and found this quote from Soviet and Russian Lunar Exploration by Brian Harvey:

” On the third day, two hours before landing and 8,500 km out, the Luna 7 oriented itself for landing. Unlike Luna 5, it was on course for its intended landing area near the crater Kepler in the Ocean of Storms. As it did so, the sensors lost their lock on Earth and, without a confirmed sensor lock, the engine could not fire. This was the second time, after Luna 4, that the astro-navigation system had failed. Ground controllers watched helplessly as Luna 7 crashed at great speed.”

Perhaps we should have heeded those last words “…..crashed at great speed.”

Tom128 also enhanced the image further. He said “My thought is that what we now see is the craft/wreckage with main body upside down and this rod pointing upward.”

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Members of the Moon Zoo team initially thought it worthy of a closer look but then the Voices of Reason stepped in. Chris Lintott reminded us that our object was at the wrong western longitude to be Luna 7 and Phil Stooke champion of locating spacecraft debris on LRO images advised that although the shadow did look unusual it was likely to be nothing more than the type of linear shadow he had seen many times before of an appropriately placed and shaped rock near the terminator. And he quite rightly stressed that it is known that Luna 7 crashed which means we shoud be looking out for a small crater rather than spacecraft debris.

So were we just seeing what we wanted to see or is there really something there? Another view with overhead illumination would certainly help. But until then the speculation will continue. The full forum thread is here.


Jules is a volunteer moderator for the Moon Zoo Forum.

Apollo 12 and Surveyor 3

Here is a seldom posted photograph showing Surveyor 3 from Block crater which is a small crater just inside the rim of Surveyor crater.  The Apollo 12 lunar module Intrepid, not shown, would be behind astronaut Alan Bean who took the photograph.  Notice the astronauts’ path in the regolith at top of Surveyor crater moving along the rim.  Click on NASA link below for an incredible view (click on photo to magnify).  Apollo 12 landed on the Ocean of Storms on November 19, 1969.

http://history.nasa.gov/alsj/a12/a12pan1344009rdmh.jpg

http://www.lpi.usra.edu/lunar/missions/apollo/apollo_12/surface_opp/

Below is a photograph mosaic taken by Surveyor 3 that shows Block crater right of center.  Surveyor 3 landed on April 20, 1967.  Its camera is pointed in the direction where Alan Bean would be standing and aiming his camera at Surveyor 3 two and a half years later.  Here is a contour map of Surveyor crater.

http://history.nasa.gov/alsj/a12/NASA67-H-876-s.jpg

Surveyor 3 made scoop marks in the lunar regolith that were recorded with its television camera.  31 months later (see diagram of scoop marks) the Apollo 12 astronauts photographed them.

http://history.nasa.gov/alsj/a12/AS12-48-7107.jpg and  http://history.nasa.gov/alsj/a12/AS12-48-7098.jpg

The scoop mark in right photograph is just below the footprint.  At Moon Zoo we know that these disturbances of the regolith last a very long time and can be seen in many MZ photographs such as the landing site photograph featured later in this article.  Here is what the Apollo 12 Surface Journal says:

“Post-mission analysis indicated that, in the 31 months since Surveyor landed, no meteoritic craters larger than 1.5 mm in diameter had been created in the bottom of the footpad imprint or in the areas disturbed by the Surveyor scoop. The analysis also did not show any signs of weathering over 31 months. Erosion of features by the steady rain of small meteorites is an extremely slow process.”  You can also click here to read an analysis of Sureyor 3 material returned to Earth.

Lateral Lines in Survey Crater
The astronauts came across some very interesting lateral lines in Surveyor crater that they could not explain.  This is what they said:

133:58:51 Conrad: Oh, that is interesting! What in the hell…
133:58:52 Bean: Look at how it’s kind of made them into…Once again, it looks like something has rained on it. They’ve taken on a little…
133:58:58 Conrad: Wonder if that was from us?
133:59:00 Bean: Oh, no! I don’t think so. (Pause) Hey, you notice, there’s a general trend of lines along here from the north…that would be the northeast to the southwest. See those little lines running along through the crater here?
133:59:15 Conrad: Yeah.
133:59:16 Bean: I think I’ll take a picture of that. (Pause)

Alan Bean photographed the lateral lines below and I cropped and enlarged them to show more detail. There are several of them running along the crater and I bracketed a couple between the white lines.  Surveyor 3 scoop is shown on the left.  The dark stuff is shadow.

At the Moon Zoo Forum, we often share interesting photographs that give clues to what is happening on the lunar surface.  ElizabethB submitted this Moon Zoo photograph below. What Pete Conrad and Alan Bean may have been looking at were mini boulder tracks running through Surveyor crater.

AMZ4003k23

Intrepid descending

Forum member Caro made an outstanding composite photograph from Moon Zoo Apollo 12 pics below.  Surveyor 3 is on left side of crater (large crater left in MZ composite photograph) about half way down.  You can follow the footsteps from the lunar module descent stage.  NASA LROC article, ” First Look: Apollo 12 and Surveyor 3″ with more information.

The craters seen from lunar orbit were called Snowman and used as a landing aid.  Surveyor crater was the snowman’s main body.  The photo below is what Richard Gordon saw looking through his sextant from the orbiting command module Yankee Clipper. You will need good eyes.  Luckily an annotated version was made.  This link takes you to a NASA diagram of Apollo 12 mission ground tracking of Intrepid as it makes its approach and lands near Surveyor crater.

Apollo 12 mission commander Pete Conrad was a colorful individual who left a enduring legacy at NASA.  His biography, “Rocket Man” by Nancy Conrad and Howard Klausner is well worth reading.  Alan Bean was his lunar module pilot and later became an artist.  This video is an excerpt from an an excellent documentary on the lightning strike during Apollo 12 lift off and the near abort.

I think you will enjoy Alan Bean’s art gallery of Apollo missions.  Click on the “Entrance” icon and go to the index of collections.


Tom128 is a regular contributor to the Moon Zoo Forum.

Aristarchus

Terrain forming a cross near Aristarchus crater

Terrain forming a cross near Aristarchus crater

This week I’m concentrating on the Aristarchus region. Aristarchus crater was named after the Greek astronomer Aristarchus of Samos by an Italian mapmaker called Giovanni Riccioli.
The crater is relatively young, being formed approximately 450 million years ago and is one of the brightest craters on the nearside with an albedo almost double that of other similar features. It has a diameter of between 40 and 45km and a depth of 3.7km.

The following image of the Moon was taken by Jules and shows Aristarchus as the bright spot in the top left quadrant. It can be seen by the naked eye.


Jules

The Aristarchus area of the Moon is one of the most interesting and diverse regions on the nearside. It consists of a rectangular shaped plateau about 200km across which is located in the middle of the vast Oceanus Procellarum mare. This plateau was probably uplifted and tilted when the Imbrium basin was formed and has experienced much volcanic activity. The largest sinuous rille known, Vallis Schroteri, is found here and is about 160km long and up to 11km wide. The second article at the end of this post has a very interesting description of the head of the Vallis Schroteri rille and some great images.

The Aristarchus region has had many transient lunar phenomena (TLP) reported. When the Apollo 15 lander passed over this region in 1971 it recorded a significant rise in alpha particles which was believed to be caused by the decay of Radon-222. This radioactive gas has a half-life of only 3.8 days and is thought to be released through tidal stresses.

The following image shows the Aristarchus region. Aristarchus crater is on the left with Herodotus crater on the right and the Vallis Schroteri rille starting below it.


Nasa image from the Apollo 15 Mapping Camera

Some images of the Aristarchus area posted by users of the Moon Zoo forum:

Part of the collapsed walls of Aristarchus. Geoff
ID: AMZ400432i
Latitude: 24.199° / Longitude: 312.434°
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Impact melt in Aristarchus crater. Tom128
# ID: AMZ10036sv
# Latitude: 24.3744° / # Longitude: 312.405°
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Interesting terrain in Aristarchus area. DJ_59
ID: AMZ300013p
Latitude: 23.9853° / Longitude: 312.908°
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More interesting terrain. Thornius
# ID: AMZ2000985
# Latitude: 23.5672° / # Longitude: 312.451°

Articles

An article from LROC about the geology of the central peak of Aristarchus crater and how the different rock types exposed by the impact help geologists to see what the interior of the Moon is made from.

Aristarchus – Up from the Depths

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An article from the Space Fellowship site discussing the Cobra Head feature which is thought to be the source vent of a tremendous outflowing of lava that formed the Vallis Schroteri rille.

Aristarchus Plateau