Another Look into Daguerre Crater with LROC
In April of 1972 the Apollo 16 CSM Casper piloted by Thomas K. Mattingly orbited the Moon while Commander John W. Young and LM Orion pilot Charles M. Duke landed in the Descartes region and conducted three EVAs on the lunar surface.
Onboard the CSM was a sophisticated array of cameras that photographed the lunar surface during the 64 orbits. The panoramic photograph AS16-4511 (P) top right shows a 2 km crater near the western edge of Daguerre crater, 11.53 S, 33.11 E. I marked the WMS Image Map photo strip M121993376RE area in green, shown below and a LROC photograph of the crater is shown above, top left.
Here is a short summary about the crater from, “APOLLO OVER THE MOON: A VIEW FROM ORBIT (NASA SP-362)” on page 118:
“It shows the striking bilateral symmetry of the rays of a small (2-km diameter) crater in the floor of the large crater Daguerre in Mare Nectaris. Continuous areas and narrow filaments of light-gray ejecta extend from the crater across the dark mare surface through 270°, but are entirely absent in the southern 90° sector. Within the crater, dark material occurs on the southern crater wall while the remaining walls are bright. (The reader may wonder about the material whose reflectivity cannot be observed because it lies in shadow on the east wall of this crater. Until the area is observed under high Sun conditions, we are forced to make the simplifying assumption that it is bright because most of the materials visible elsewhere in the walls are bright.) This crater probably resulted from the impact of a projectile traveling from south to north along an oblique trajectory. Its pattern of ejecta distribution is similar to that of small craters produced by the impact of missiles along oblique trajectories at the White Sands Missile Range, N. Mex. Some observers postulate that the dark material is a talus deposit of mare material that has fallen into the crater.-H.J.M. Another geological explanation is that the unusual pattern may be due to an intrinsic characteristic of the local terrain, probably an abrupt lateral change in the composition of the bedrock within the area that was excavated. F.E.-B. ”
As a side note, Harold J. Masursky and Farouk EL-Baz were both geologists who worked with the Apollo program. Those familiar with the astronaut biographies will find many references to Farouk El-Baz.
Taking a second look at the crater with LROC, we can now see which of the two geologists was correct with a stunning picture of the dark material spreading out in a ray pattern and also cascading over the crater wall towards the crater floor.
Here is an initial analysis made by MZ team member IreneAnt about the crater and its apparent oblique impact:
“If you look carefully at the LROC image, you can see an ejecta herring bone pattern in the dark wedge portion outside the crater. I think this is good evidence that this dark wedge is ejecta. You can also see from the LROC image, that this dark wedge matches up very well with a layer of dark material in the crater wall. So, there isn’t really a missing section of ejecta here, it’s just a different colour; in the black area, you hit and excavated black material, while in the light areas, you hit and excavated light material. So, it seems that Farouk El-Baz was right and the ejecta pattern may have been caused by variations in the pre-impact target.
The thing that I find really interesting here is the implication for low angled impacts. From the Apollo images it seems clear that there is a section of the ejecta deposit that is missing, thus indicating a low angled impact. However, when you look at the higher resolution LROC image, you can see that there is, in fact, dark ejecta in the “missing” section, so this is not a low-angled impact. So, the two images tell very different stories. This casts a doubt on all “low-angle” impact craters identified based on missing ejecta sections. It may just be that higher resolution data is needed to see some ejecta of a different composition.”
Irene continues her analysis of the crater talking more about the lateral shift in the lunar material from lighter to darker:
“These kinds of horizontal variations are more common on the Moon than was originally thought. This is what my research revolves around. What probably happened here is that a small mare flow was confined by topography (hills and such) or was just too small to flow very far (think how a little bit of milk spilled on a flat table will only flow so far). Another possibility is that this is a pyroclastic deposit. Sometimes volcanoes can explode like a shaken bottle of pop. When this happens, drops of lava cool as they fly from the vent and land on the ground as glass beads. These kinds of deposits stay near the source vent, since glass beads don’t flow as well as liquid lava does. One final possibility is that this is a pond of impact melt from the Daguerre impact event. Impact melt would have been confined the same way as a lava flow.”
Irene presents very interesting information on the dark colored ejecta and iron:
“You can learn a bit more by looking at the composition of the material in and around the crater. In this image, you can see the iron content (calculated using data from the Clementine mission) overlain on a Lunar Orbiter image of this exact crater. The colours represent various iron contents (in Weight % FeO), as identified by the colour bar on the right. The shading represents topography through the use of shadows (sun is shining from the right). You can see that most of Daguerre’s floor has relatively high iron content (greens and yellows), while the rim of Daguerre (top right of the image) is relatively low in iron (blues). Our LROC crater seems to have excavated mostly material that is less iron-rich (light and dark blues), except for the wedge of high iron (greens and yellows) at the bottom of the crater. This high iron wedge corresponds exactly to the dark ejecta section you can see on the LROc image.”
I marked the wedge section with white lines and circled the approximate outer rim of the crater. The white rectangle in the crater indicates no iron content.
“If you zoom in, you can see that the iron-rich wedge at the bottom of the image extends into the crater interior. Remember that only parts of the crater interior are in shadow. To get a feel for the extent of the entire crater, complete in your mind the circle that is suggested by the right edge of the shadow section. Then you will see that the green wedge does indeed extend inside the crater. It is possible that the iron data is registering the land slide of dark material that we can see down the crater wall in the LROC image.
There is a high likelihood that the dark layer, which was the source of the ejecta that created this iron-rich wedge, is basalt. It is also possible that it may be a pyroclastic deposit, where the glass beads re-crystallized into basalt-type minerals after they solidified. The dark ejecta wedge, is expected have the same composition as this source layer.
The lighter ejecta material is highland material. It is lighter in color because of its lower iron content. It was emplaced when this impact crater excavated either sections of Daguerre’s crater wall and slump terraces or some pre-existing highland ejecta from an older and large crater. There’s not enough information here right now to tell which of these was excavated by our LROC crater, though. Lots more work to be done!”
I would like to thank Irene for taking the time out from her busy schedule to make this outstanding analysis of the crater. Forum moderator Jules and I also had some fun with a speculative comparison of the crater using the photographs of Apollo 16 and LROC.
Tom128 is a regular contributor to the Moon Zoo Forum
Irene Antonenko is a Moon Zoo Team member
Merry Christmas Moon Zoo!
to everyone involved in the Moon Zoo project!
On top of the Christmas tree is the snowman from Apollo 12. The other images are some of the lunar “snowscapes” that have been posted on the forum including Santa’s Christmas stocking (from Aristarchus.)
Since Moon Zoo launched back in May we have spent 7 months measuring craters, comparing boulders, posting stunning images, finding the unusual and unexpected and chatting about anything and everything. A real community has developed on the Moon Zoo forum and I hope more people will join us there in the New Year.
Forum member Tom128’s Moon Zoo word cloud spaceship courtesy of wordle.net gives a flavour of some of the forum topics.
So wherever you are and however you will be spending the Christmas holidays try to find a few spare moments to go outside and look up at the Moon. There will be a total lunar eclipse on the 21 December visible to many of us followed by a photogenic waning Moon over the following few days. And spare a thought for the Lunar Reconnaisance Orbiter spacecraft as it carries on doing its job so that we can carry on doing ours.
And don’t forget the Zooniverse Advent Calendar for some more astronomical tricks and treats from the Zooniverse team.
Jules is a volunteer moderator for the Moon Zoo forum
Apollo 17…… 38 years on
image AS17-134-20471 from the Apollo 17 Image Library.
This iconic image was taken 38 years ago today. It shows Apollo 17 astronaut Harrison “Jack” Schmitt next to the Lunar Rover during an EVA on December 13th 1972 with the crescent Earth hanging in the sky.
This week marks the 38th anniversary of the Apollo 17 mission to investigate the Taurus Littrow valley region of the Moon. The mission launched at 12.33am EST on December 7 1972 and ended on 19 December when the 3-man crew splashed down in the Pacific Ocean just 640 meters from the target point.
Apollo 17’s mission plan was for the spacecraft to land in the Moon’s Taurus-Littrow region near the rim of the Serenitatis Basin as this region was rich in a variety of lunar geological features such as volcanic cinder cones, highland mountains and many large boulders which had rolled down the North and South massifs. This meant that the crew could investigate young volcanic rock as well as older highland material at the same location. Debris from Tycho Crater’s rays also extended this far. The Apollo 17 crew collected 111 kilograms of lunar soil and rock, 741 individual samples, including a 3 metre deep drill core. This was the biggest and most varied collection of lunar materials returned by any Apollo crew. The mission had the experience of the whole Apollo programme to draw on and from lift off to splashdown it was flawless. A fitting end to an inspirational space programme.
One of the outcomes of the Apollo 17 mission was the distribution of so called “Goodwill moon rocks” – portions of a rock that Jack Schmitt picked from the floor of the Taurus-Littrow valley (since labelled sample 70017.) In Eugene Cernan’s words:
|“Jack has picked up a very significant rock, typical of what we have here in the valley of Taurus-Littrow. It’s a rock composed of many fragments, of many sizes, and many shapes, probably from all parts of the Moon, perhaps billions of years old. But fragments of all sizes and shapes — and even colors — that have grown together to become a cohesive rock, outlasting the nature of space, sort of living together in a very coherent, very peaceful manner. When we return this rock or some of the others like it to Houston, we’d like to share a piece of this rock with so many of the countries throughout the world. We hope that this will be a symbol of what our feelings are, what the feelings of the Apollo Program are, and a symbol of mankind: that we can live in peace and harmony in the future.”
Jack Schmitt continued:
Three months after Apollo 17 returned home fragments from the rock that Cernan and Schmitt collected were distributed to 135 foreign heads of state, the 50 U.S. states and its provinces. Each rock encased in acrylic was mounted to a plaque with the recepient’s flag (which was also flown to the Moon.) The samples to the 135 foreign heads of state also included a letter signed by President Nixon. In all nearly five hundred tiny pieces of the sample have been distributed to museums and researchers around the world though NASA still has about 80% of the rock. There is an analysis of sample 70017 here.
Apollo 17 has been a popular topic on the Moon Zoo forum. Forum regular Caro was the first to post a couple of images of the Apollo 17 landing site back in May which together show the Challenger descent stage (visible in the left image, surrounded by trails made by astronaut feet and the wheels of the lunar rover which is visible as a dark spot on the left edge. The US flag is just below Challenger and scattered around the site is various ALSEP debris (Apollo Lunar Surface Experiments Package.) Many other forum members have “rediscovered” the Apollo 17 landing site since.
|Further forum resources:
Apollo 17 resources thread
Dark Haloed Craters
Transient Lunar Phenomena
The UK Goodwill Rock Hunt
|Apollo 17 Internet resources:
Apollo 17 Image Library
LROC site and video of the landing site
Apollo 17 Lunar Surface Journal
LROC NAC image
Forum member NGC3172 (Nathaniel Burton-Bradford) produced this 3D anaglyph of the landing site:
Ronald E. Evans (Command Module Pilot), Harrison H “Jack” Schmitt (the only geologist to have walked on the Moon) and Eugene A. Cernan were the 3 Apollo 17 crew members. Just before he returned to the Lunar Module for the last time Eugene Cernan said:
“ As I take man’s last step from the surface, back home for some time to come — but we believe not too long into the future — I’d like to just [say] what I believe history will record — that America’s challenge of today has forged man’s destiny of tomorrow. And, as we leave the Moon at Taurus-Littrow, we leave as we came and, God willing, as we shall return, with peace and hope for all mankind. Godspeed the crew of Apollo 17.”
But despite the hope and optimism of Eugene Cernan’s words the thrill of landing a man on the Moon had passed. The Apollo mission had finally ended and the prospect of further funding and support for manned space exploration looked bleak. 38 years later Eugene Cernan is still the last man to have walked on the Moon.
Thanks to forum member Tom128 for the Goodwill Moon rock links.
jules is a volunteer moderator for the Moon Zoo forum
Moon Zoo Author Poster
Day 10 of the Zooniverse Advent Calendar brings us to the Moon Zoo blog with a pair of posters from two different eras – and two different perspectives.
On Christmas Eve 1968, the crew of Apollo 8 wished a Merry Christmas to the people of Earth by showing them the image of themselves, in this famous Earthrise image. Flash-forward to 2010, and now, thanks to NASA’s Lunar Reconnaissance Project (LRO) and the Moon Zoo project, the people of Earth can see the Moon just as clearly as the 1968 crew that orbited it.
When it came to producing the Moon Zoo edition of our author posters series, it was hard to pick the most appropriate image – 1968 or 2010 – so instead we made both! Two posters, created from the 36,000+ names of the people who gave permission to be published.
Download large LRO poster (27 MB) or small (14 MB). Download large Earthrise poster (27 MB) or small (14 MB).
Franklin’s Bright Spots
I searched the forum for something new to post in this week’s slot and I found an image posted by Tom128, yesterday. It’s an interesting feature in Franklin Crater and I believe Tom’s post is the first for this.
The direction of sunlight and the angle of the terrain make these bright areas really stand out but why are they so bright? Is it just the angle of light and topography? Or maybe there is something in the surface material, here.
Tom128 included the a link to the strip. This region can be found at bottom of the strip. You can also zoom further in from here: M111279662LE
The original post is in TLP project –Notched cavities in lava.
Moon Zoo Image of the Year
The Moon Zoo forum has elected this curious portion of the Moon’s surface as the 2010 Moon Zoo Image of the Year. Named Ina, this puzzling lunar feature may be the result of fairly recent volcanic activity (millions rather than billions of years old) with two distinct types of terrain: rough jagged rubble-like brighter areas and smoother, darker mounds. No-one knows for certain what caused these two different types of terrain but one view is that it is the result of a “recent” gaseous outburst which has removed part of the top layer of regolith.
The Moon is full of odd and peculiar features and it is fitting that Ina has been elected the favourite so far. The Moon Zoo forum and this blog have become places to discuss just such odd features. So congratulations to the Moon Zoo community on an amazing first year – and may we find many more ‘Ina’s in the future.
If you want to learn more about Ina, you can read an excellent NASA article explaining more about it.