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.
To celebrate the very first International Observe the Moon Night on 18 September 2010 Moon Zoo set 2 challenges. Zookeeper Rob blogged about one challenge which involved the launch of the Moonometer.TM Between September 15th and 19th the Moon Zoo community were challenged to classify 20,000 images, a vast area of the Moon equivalent to 2 Chicagos.
This proved to be easy and we blasted through the target within 48 hours! The stakes were upped to 40,000 images (or 40 Manhattans.) Again the Moon Zooites rose to the challenge and 24 hours later the second target was smashed and a third and final target of 60,000 images was set (that’s equivalent to 10,596 Disneylands!) 24 hours and 60,000 images later the Moon Zoo Community had reason to be proud.
We celebrated International Observe the Moon Night in style – inside, warm and cosy looking at images of the Moon in unprecedented detail while (for some of us, at least) the clouds descended, the winds howled and the rain fell preventing any real time observations.
And the good news is that the MoonometerTM is here to stay!
The second challenge was a photographic one. Not the easiest challenge given the inclement weather in some areas but nevertheless we rose to the challenge and this is the result – a mixture of daytime, night time, arty and abstract Moons:
Jules is a volunteer moderator for the Moon Zoo Forum.
Did you know that Moon Zoo users have now classified an area three times the size of Wales? Or maybe you’d be interested to learn that, even on slow days, Moon Zoo users trawl a section of the Moon bigger than 500 Disneylands!
To celebrate International Observe the Moon Night we have launched the Moonometer™ – a fun way to understand how much work Moon Zoo is doing minute-by-minute. In addition, between September 15th and 19th we are challenging the Moon Zoo community to classify a huge chunk of the Moon: 20,000 images! This is roughly equivalent to an area twice the size of Chicago!
To take part in the challenge all you have to do is classify things on Moon Zoo using either the Crater Survey or Boulder Wars tools. The Moonometer™ keeps track of the number of LRO images that have been classified and converts them into approximate equivalent areas.
You can also keep track of activity on Moon Zoo via the Moon Zoo Live! page. Here you’ll find ever-updating maps that show how Moon zoo is connecting the Earth to the Moon thanks to our users.
International Observe the Moon Night is all about learning more about the Moon going and taking a look at it. You can use our Explore the Moon pages to find out more about our nearest neighbour in space. To get involved with the Moon Zoo community, visit our forum and see what we’re currently talking about and looking at.
Moon Zoo team member Katie sent me an e-mail with a link to an article about a newly discovered lunar feature!! The feature is a natural bridge likely formed by a dual collapse into a lava tube. The one Katie linked to is one of 2 found in the impact melt around King Crater on the lunar farside. This and a smaller neighbouring bridge (also in impact melt material) are the only examples of natural bridges that have been found on the Moon and she asked if we could look out for some more.
These are similar to the lava tube skylights we are already looking for and might be quite tricky to spot. Look out for 2 or more “holes” and some evidence of sunlight shining through from one hole to another showing that it really is a larger cavity spanned by a “bridge.”
You might come across bridges in impact melts (like the King Crater bridge) or in rilles (valleys carved out by lava flows or created by the collapse of lava tubes) running over the mare basalts. Rilles may have some uncollapsed roofed over sections. These are the natural “bridges” we should look out for.
The area around King crater seems a good place to start. Have a look at these LROC strips showing the King Crater bridge under different illumination:
Other locations rich in impact melt would also be good hunting grounds. In large impacts the impact itself and the damage caused by shock waves raises the temperature of the surrounding area and significant amounts of lunar rock melt or vaporize together with the original impactor. Some of this impact melt rock is ejected, but most remains in or around the crater. Impact melt can be seen as flows or ponds.
More information about about impact melt can be found here:
BYRGIUS A CRATER IMPACT MELTS – AN LROC PERSPECTIVE. There is more about Byrgius A here.
IMPACT MELT MOVEMENT IN LUNAR CRATERS.
IMPACT MELT FLOWS ON GIORDANO BRUNO.
These features are interesting to lunar scientists because they are essentially covered caves and ideal places to build future Moon bases as the bridge roof will offer protection from solar wind and cosmic ray radiation. There’s a paper on how bridges may form here: A Search for Intact Lava Tubes on the Moon: Possible Lunar Base Habitats.
This is the King Crater Bridge from LROC image number M113168034R with what I think is the second bridge. Can you find a better candidate for the second one? The small blue rectangle in the inset shows the locations.
Thanks to Katie for additional info and links.
Jules is a volunteer moderator for the Moon Zoo Forum.
A recent article that appeared in the journal Science led to a flurry of shrinking Moon headlines. Don’t worry, the Moon is still there, and will be for some time yet. But seeing as the images for this study came from the LROC camera that we all know and love, I thought it’d be worth re-telling the story here.
Figure 1. A perspective image looking across the Taurus-Littrow valley, made from LROC stereo images M104311715LE and M104318871LE. The arrow shows the Apollo 17 landing site, with the Lee-Lincoln lobate scarp in the left of the image. This scarp runs across the valley floor mare and up through highland material. Credit: NASA/Goddard/Arizona State University/Smithsonian
Lobate scarps are probably amongst the smallest tectonic features on the Moon, and so they are too small to be visible in telescopic images, but rather only the highest resolution images from orbiting spacecraft. In the past they were only visible in Apollo Panoramic Camera high resolution images, which only covered a tiny portion (about 20%) of the Moon near the equator.
So there wasn’t really a detailed understanding of where these features occurred as the image coverage wasn’t good enough. We had basically been limited to the 40 year old data that were available.
The general consensus is that lobate scarps form by contraction of the upper crust and so are a form of low-angle thrust fault (see Amanda Nahm’s excellent blog post on lunar faulting here), which are common geological features on the Earth. But we have a slightly harder time explaining their formation on other planetary bodies, mainly because we can’t rely on plate tectonics to provide the driving force. So what does cause the contraction that is responsible?
On relatively small planetary bodies, like Mercury and the Moon, it’s long been thought that the original cooling of the body very early in its history could cause a global contraction in the size of the body (this is a fairly familiar concept to anyone that has played as much winter sport in England as I have – some things get smaller as the temperature decreases). The original higher temperatures are probably the result of a combination of the heat left over from accretion (formation) of the original body, and from the decay of short-lived radio-isotopes.
Alternatively, tidal forcing can also cause tectonics, both extensional and compressional, on planetary bodies when there is a tidally-locked moon involved. For example, Europa is covered in so-called cycloid fractures thought to be the result of the massive tidal forces occurring in the inner Galilean satellites. In this case the body is pumped and squeezed by the tidal forces, causing fracturing (Europa) or even frictional melting (Io).
However, these two different possible causes of stress in the upper crust would produce different tectonic features at different places on the surface. Tidal forcing would cause contraction and thrust faults (including scarps) at the tidal bulge and its antipode (so near the equator), but would also cause extension and normal faulting at the poles. In contrast a global period of cooling would cause contraction over the entire globe of the body, rather than just at or near the equator.
So the increased coverage offered by LROC meant that the search for lobate scarps could, for the first time, be extended beyond the equatorial region and in effect test the hypotheses for the cause of the crustal stress on a global scale. By scanning through LROC images the authors saw not only the previously identified lobate scarps, mostly near the equator, but also crucially identified lobate scarps close to the polar regions (see Figure 2)
By observing these lobate scarps at high latitudes, this study has shown that the major tectonic force near the poles was probably compressive, rather than extensional, and so doesn’t fit well with the idea that tidal forcing (alone) has caused lobate scarps to form, but instead supports the idea that they are primarily the result of contraction over the entire lunar globe.
Figure 2. This map illustrates the distribution of lobate scarp features located thus far. Black dots indicate previously known scarps while white dots depict newly detected scarps found in images from the Lunar Reconnaissance Orbiter Camera. Credit: NASA/Arizona State University/Smithsonian
The apparent age of these scarps is also very interesting. Although it is notoriously difficult to estimate the age of structural features like these (as they are so small), it is possible to estimate an upper age from dating the material in which the scarps have formed. In planetary science this dating is most often done by looking at the relative age of different features (so, what came first?) and also by counting the number of impact craters in a given area (hence the crater survey in Moon Zoo!). The authors estimate that the material that these scarps form in is less than a billion years old, which is relatively young for a geological process on the Moon.
This study has then taken this idea further and compared the estimated stress observed at the lobate scarps and compared it to the amount of stress predicted near the surface throughout the history of the Moon by different models of global cooling and contraction. What the authors suggest is that the models that fit best with the young age of the scarps predict that the Moon has undergone relatively little global contraction when compared to Mercury. I guess we’ll be able to compare better after NASA’s Messenger mission goes into orbit around Mercury in March 2011.
I think it’ll be really interesting to see the distribution of lunar lobate scarps once LRO has completed a few more years of its mission, when there is much better coverage of the lunar surface. For example, if these scarps occur at all latitudes, but only in specific regions, then could that be evidence that it wasn’t a global cooling and contraction, but rather a more regional process? And, bearing in mind the difficulty in dating these features, are all these scarps the same age? That surely would be a good thing to know, as that would really test the idea that it is a global process.
I couldn’t let this blog post pass without giving in to my love for all things Apollo. The study mentions a specific lobate scarp called Lee-Lincoln, which is in the Taurus-Littrow valley explored by Apollo 17 (shown in Figure 1). The astronauts Gene Cernan and Harrison (‘Jack’) Schmitt even drove up the lower slope of part of this scarp, and Schmitt (the geologist) described it as “very rolling and relatively smooth”. So, although these features are pretty obvious to look at from orbit (when you have the right lighting conditions), they probably wouldn’t be all that dramatic to look at from the surface. That said, Cernan claims the lunar speed record for coming down off the slope of the scarp in the rover. So maybe it wasn’t that shallow after all!
Figure 3. Apollo 17 traverse map of the Taurus-Littrow valley. Lee-Lincoln scarp is to the left of the image. Note that the illumination is from the right. The image is about 12.5 km across. Credit: Lunar and Planetary Institute.
If you want to read more about Apollo 17, or the other missions, I heartily recommend visiting the Apollo Lunar Surface Journal, which is an absolute fantastic resource. For the EVA near to the Lee-Lincoln scarp, head to the second EVA and geology stop 3, for transcripts, photos and much more.
Figure 4. Photography of the Lee-Lincoln scarp taken by Jack Schmitt (Apollo 17) taken between geology stops 2a and 3 during EVA-2. The scarp can be seen running through the left of the image, with multiple lobes, and up into the highland material making up the North Massif. 70 mm Hasselblad camera image AS17-138-21118, magazine 138/I. Credit: NASA/Apollo Lunar Surface Journal.
So, although this isn’t a call-to-arms to go lobate scarp hunting, please do keep an eye out for them in future images in MoonZoo.
Crater chains are just one type of feature we are looking out for in Moon Zoo but they are proving to be rather elusive. A number of processes can leave a chain of craters (a Catena):
- Boulders from a larger impact are flung out and form smaller secondary craters where they land. The larger the impact the further away the ejected boulders are thrown. In really large impacts ejecta can be hurled hundreds of kilometres away. Some boulders land on their own forming isolated small craters; a group of boulders landing together can form a ridged herringbone pattern and a string of boulders landing together can form a chain of craters which fall radially to their parent crater. Individual craters in the chain are also usually elongate in shape (due to the shallow angle of impact) with irregular rims and the ejecta appears ‘splashed’. Isolated secondary craters are often difficult to identify but craters in chains are easier to spot and can, therefore, be studied as secondary craters.
- The impact of a fragmented meteorite or comet might also have created a crater chain.
- Some crater chains are thought to be volcanic in origin but it can be difficult to distinguish between the two types of crater chains. Volcanic crater chains are lined up along a common fault or set of faults, and each crater produces a blanket of volcanic ejecta. As you would expect, volcanic crater chains are not assocated with a parent crater.
There are many – too many – examples of three or four small craters in a line and while these may well be secondary craters from a larger impact they are not especially noteworthy. Some of the more famous crater chains are very impressive and contain over 20 smaller craters. It would be quite something if we could find an example like that.
These are some of our contenders so far:
Posted by Forum member Caro:
Moon Zoo team member Irene Antonenko says:
“The wispy, feathery texture associated with crater chains is formed when the ejecta deposits of the craters in the chain interfere with each other during their emplacement (kind of like point-source waves interfering in a wave tank.)”
Discussion on the forum concluded that the impact angle was so low that the top part of the impactor sheared off and bounced to form the “tail.”
If you want to read more about Crater Chains try these links:
Finding a good, clean example of a long crater chain, whether volcanic or impact in nature, is this week’s challenge!
Jules is a volunteer moderator for the Moon Zoo Forum.
In Anthony’s Looking For Change blog he says that we should be looking out for any interesting surface features that may have been freshly disturbed or contain a vent from which outgassing has occurred. “TLP” projects have been set up in the forum for each of the features mentioned, except for Deep Seated Fractures and another feature, “Atmospheric” phenomena (which was not mentioned by Anthony).
Deep seated fractures can be found on some images from LROC but “Atmospheric” phenomena will probably not be found. Some images taken during the Apollo project had fuzziness along the horizon when it was expected that the horizon would be sharp-edged. This may have been caused by dust particles suspended above the lunar surface by electrostatic charging.
Deep Seated Fractures
The one feature which Anthony mentioned and which is not covered in the other TLP Project threads is deep seated fractures and he uses an example from the floor of Tycho crater:
Tycho Crater floor, from LROC image M114031031LE
One of the Moon Zoo users, ElisabethB (Els), found something similar near Proclus crater:
Sun Angle: -76.23°
Scale: 0.50 meters / pixel
Zoom Level: 3
Apollo 17 astronauts saw and sketched what they called “bands”, “streamers” and “twilight rays” which were visible just before lunar sunset or sunrise. These rays were also seen by astronauts on the Apollo 8, 10 and 15 missions.
from Nasa Media Library
On the side of the Moon in daylight, the solar radiation knocks electrons out of atoms and molecules in the regolith. A positive charge builds up which is sufficient to loft particles 1 micron and smaller in size above the surface. These particles can go up more than a kilometre.
The Moon seems to have a tenuous atmosphere of moving dust particles. We use the word ‘fountain’ to evoke the idea of a drinking fountain: the arc of water coming out of the spout looks static, but we know the water molecules are in motion. In the same way, individual bits of moondust are constantly leaping up from and falling back to the Moon’s surface, giving rise to a “dust atmosphere” that looks static but is composed of dust particles in constant motion.
[quote byTimothy J. Stubbs, of the Laboratory for Extraterrestrial Physics at NASA's Goddard Space Flight Center]
It is believed that the dust on the night side of the Moon is negatively charged due to electrons from the solar wind flowing around the Moon onto the night side. So at the Moon’s terminator between the positively charged dust of the daylight side and the negatively charged dust of the night side, there could be flows of dust which may resemble auroras.
The four links below from NASA discuss various aspects of this phenomena:
The Boulder Tracks thread is one of the most popular within the Moon Zoo forum and we have some amazing tracks posted there.
Boulder tracks are important to the Moon Zoo project – the following quote is from one of the Moon Zoo team members:
One of the main reasons we are asking Moon Zoo users to search for scars left behind by tumbling boulders is to help support future lunar exploration initiatives. Boulders that have rolled down hillsides from crater walls, or massifs like the Apollo 17 landing site, provide samples of geologic units that may be high up a hillside and thus difficult to access otherwise by a rover or a manned crew vehicle. If mission planning can include traverses to boulders that have rolled down hills, and we can track these boulders back up to the part of hillside from where they have originated, it provides a neat sampling strategy to accessing more geological units than would have been possible otherwise… Thus we hope to use Moon Zoo user data to produce a map of known boulder tracks (and terminal boulders) across the Moon. - Katie Joy
Recently ElisabethB (Els) posted the tracks shown below. Quite an amazing variety of track sizes and shapes! The track on the bottom appears to have mounds inside the track caused by the shape of the boulder that created the track.
Also, some of the tracks have craters overlapping them which may have been caused by the same impact. The original impact would have sent boulders bouncing and rolling along the regolith but would also have sent boulders upwards and they would have eventually fallen back and created craters.
The area where these tracks are found is Montes Alpes / Vallis Alpes.
Sun Angle: -62.71°
Scale: 0.51 meters / pixel
Zoom Level: 3
Time for a bit of light relief.
While looking for sinuous rilles, lava tube skylights, grabens and bits of discarded spacecraft, and in between counting boulders and measuring craters, forum members have also found several possible treasure hoards obviously left by previous visitors to the Moon……
You might be fooled into thinking that these crosses are not the mark of Lunar Pirates at all but that they have been caused by the forces of Lunar geological processes. Maybe the stresses involved in crater formation on boulders landing heavily after being flung out over hundreds of metres just happened to cause them to crack by chance to form an “X.” Or you might suggest that the LRO camera took the image when the angle of the Sun was just right to catch a rocky rim and cast an “X” shaped shadow across the crater floor. You might even surmise that the albedo of the Lunar regolith just happens to resemble an “X” when viewed in a certain light.
But you would be wrong! We know different!
There’s treasure to be had, they obviously didn’t cover their tracks very well and we are on to them!
We are keeping the coordinates to ourselves but can you see where “X” marks the spot in these images?
Jules is a volunteer moderator for the Moon Zoo Forum.
One thing that I have learned here at Moon Zoo as a full member-newbie is that when considering the lunar landscape what is dark may not be black and what is light may not be white. A case in point is this photograph that stumped me shortly upon arrival at Moon Zoo.
Luckily, Forum moderator Thomas J introduced me to a term called albedo. He said:
“There are a number of reasons for this change in shade. The reflectivity of the surface material is known as its albedo; material that is highly reflective will have a higher albedo than that which is not as reflective. In some situations certain areas may display high albedo material due to geological activity such as impact effects, volcanic effects and even Moon quakes. It is, therefore, not uncommon to see two contrasting shades in adjacent regions. Also, the Moon’s surface is not flat, the topography rises and falls with slopes, hills and mountains. When the Sun is low in the sky a slight slope downward can leave an area in shade. So, in this image it may be that the material on the right has a higher albedo, or it may be a downward slope on the ground level to the left with a rise to that on the right.”
Why do the tracks of the astronauts on the lunar surface appear darker than the surrounding area? One answer from spacefellowship.com is:
” This effect is most likely due to compaction of a very loose surface powder by simply walking around. The more walking in a given area, the more compaction that takes place, and thus the lower the albedo.”
We know certain areas of the lunar surface have coloration due to crater impacts and lava flows such as the famous orange soil of Apollo 17 near Shorty Crater but generally the lunar landscape was described by the Apollo astronauts as concrete, mouse grey and/or light brown in color.
This brings me to the Apollo 12 lunar sample 12047,6 that is now on loan from NASA to the Seattle Museum of Flight.
Apollo 12 astronauts Pete Conrad and Alan Bean collected this specimen while at the mare region called Ocean of Storms. It is an Ilmenite Basalt sample. From the black and white photograph you can tell that it is a concrete like color not unlike many of the photographs we view here at Moon Zoo. What is interesting is that there is more to this specimen than what you see here and read about in the paper linked to above and that is the albedo effect and color change.
I happen to be lucky and live about 15 miles from the Seattle Museum of Flight. However, it was not until I viewed an online photograph of NASA 12047,6 taken by an amateur photographer visiting the museum that I found out that the sample was on display there. On my first visit I was perplexed as the sample did not look quite like the beautiful one in the photograph but more like the concrete colored black and white photograph, though not quite as drab looking. For a month or so this mystery nagged on me and I went so far as to question the on site guides about the authenticity of the display item. Maybe it was another sample or a copy. However, I was told that it is a genuine lunar sample.
Searching the internet I found reference to color change on the lunar surface:
“The orbiting Apollo astronauts noticed a peculiar phenomenon when they observed the lunar surface at a small angle related to the sun’s light. At such small angle, the lunar surface appeared warm brown colored.”
Yes, the light bulb went on in my head and I returned to the museum several months later. When moving as close to the display case as possible and viewing the lunar rock at a sharp angle, the brown color showed up. So, here is a photograph of NASA 12047,6 taken at the Seattle Museum of Flight by amateur photographer Svacher. Just as the astronauts did, we can see the brown color of the lunar surface when the sun or in this case the viewer is correctly positioned.
Here’s some more related reading:
And thanks to Moon Zoo Team member Katie Joy for providing the following additional information and links:
Lunar Sample Atlas
Katie says: “Thin or polished samples of lunar rock can be quite pretty. Some have hints of orange (glass), others bright green (the mineral olivine), some pink (the mineral spinel.) When you view them under the microscope using polarized light rather than direct light then all the minerals appear as a really bright range of colours and look like a stain glass window.”
A Final Thought:
Being one of many amateur scientists here at MZ, the notion of albedo and color change as it applies to larger natural occurring and unaltered geology samples comes to mind such as the Apollo 12 lunar sample above. Here the surface of the sample is in its natural state showing the color change in the visible light spectrum similar to what the Apollo astronauts would have seen in similar lighting conditions.
Analyzing existing samples at the Johnson Space Center in their natural-unaltered state (if not already performed) while replicating the effect of a lunar sun at all possible angles may provide valuable information about the lunar landscape – a more holistic perspective. It may also give clues to color change of lunar formations helping to explain some anomalies associated with transient lunar phenomena.
Mapping color change of the lunar landscape at specific areas may be a helpful tool to acclimate astronauts as they once again walk on the Moon.
Tom128 is a Moon Zoo participant and a regular contributor to the Forum.