Tag Archive | Craters

Mysterious Craters

Forum member jaroslavp was presented with this Moon Zoo image a few weeks ago:

ID: AMZ1001i8l (Nr Apollonius on the edge of Mare Spumans / Mare Fecunditatis)
Latitude: 3.71611°
Longitude: 56.6751°

Intrigued by the elongated shape of the crater he went on to investigate and what he found posed us all with an interesting crater conundrum. jaroslavp commented that the marked crater looked very different under different solar illumination. In one image it looks like any other round crater. In the other it looks very elongated and is surrounded by bright material.

NAC image: M111219210LE Incidence angle 35.13
NAC image: M119482862RE Incidence angle 57.64

Moon Zoo Team Science member astrostu was impressed and thought this was an excellent example to use to highlight the effect that different angles of solar illumination can produce.

jaroslavp wondered if the round crater was actually new, maybe a recent meteorite impact: He said:

“Maybe the crater wasnt there before? When I look on the dark spot there is no sign of the crater we can see on the second picture. And maybe the sun 45° from the surface makes many things invisible that you can see on the dark picture for example fresh white and dark-haloed craters.”

After some forum discussion it became clear that this really is just the result of viewing the same crater under different illumination but it certainly got us thinking and it is the best example yet we have had on the forum of just what a difference lighting can make as this animation jaroslavp put together shows:

Now on a roll, jaroslavp then found another strange crater containing a chain of 4 smaller craters and noticed something on the right hand slope of the crater wall:

ID: AMZ10018h5 (Taurus Mountains region)
Latitude: 20.8721°
Longitude: 30.8742°

NAC image: M106676354LE
NAC image: M104318871RE

So – is the small chain of secondary craters overlying the featured crater from a different crater impact or from the same impact that created the host crater?

Every day something intriguing is posted on the forum. It’s a great place to discover the Moon!


Jules is a volunteer moderator for the Moon Zoo forum

Absorb yourself in Tycho

Appropriately named after one of the most colourful characters in astronomy, Tycho Brahe, Tycho is one of the most prominent craters on the Moon with its large, bright ray system dominating the southern hemisphere. Tycho is 85 km (53 miles) in diameter and is a relatively young crater at 108 million years old. Because it is young the rays have not been degraded and dulled by meteorite and micrometeorite impacts and still have a high albedo. So extensive are the rays that samples of impact melt glass thrown out by the impact that created Tycho were collected by the Apollo 17 astronauts from the Taurus Littrow region 2,000 km away. Tycho and it’s rays are most spectacular when viewed at full Moon when the Sun is overhead.


image: jules

The Lunar Reconaissance Orbiter Wide Angled Camera gives us a very different view of Tycho. Here we see the well preserved terraced crater walls and central mountains which are just visible in binoculars. So fresh are the features in Tycho that it is the perfect place to study the mechanics of how an impact crater forms.

click for high res version from NASA.

And here’s a close up of the rugged crater floor.

LROC

More information and another close up picture in this LROC News System article.

The NAC images of Tycho are well worth a tour. There are many NAC images of the crater floor – search on Lat -43, Long -11. Here are a few to start with:
M102230053LE
M114031031LE
M129369888LE

Enjoy! You may be some time!


Jules is a volunteer moderator for the Moon Zoo forum

Big Bangs in the Solar System

Hello all. I have written a few Moon Zoo blogs about different aspects of lunar geology and the geological history of the Moon, here, I thought I would share with you the lunar research topic I am currently working on. I hope that it is interesting and if you have any questions please do let me know. Katie Joy

The Moon’s surface is absolutely covered in impact craters (Figure 1). These range in size from the behemoth South Pole-Aitkin basin, which is a staggeringly ~2500 km in diameter and 13 km deep, all the way down to microscopic impact craters on glass beads that are less than a millimetre in diameter. No matter the size, the one thing all these impact craters have in common is that that they were created when something smashed into the Moon at high speed on the order of 15 km/sec or more (that’s pretty fast when you consider a bullet out of shotgun travels at about 0.9 km/sec).

Impacts have changed the surfaces of all rock and ice planetary bodies in the Solar System, including the Earth. However, they are so well preserved on the Moon that we can use lunar impact craters and lunar impact rocks that were made when these craters formed, to reveal the history of impact bombardment in the whole of the inner Solar System through the past 4.5 billion years.


Figure 1. Impact craters and basins on the Moon are clearly seen in topography maps of the Moon. The gigantic South Pole-Aitkin basin (labelled SPA) is located on the southern part of the far side of the Moon. Credit: Clementine mission/NASA.

When did the Moon get bombarded?
We know that a lot of large projectiles hit the Moon early in its history, and that the rate of bombardment rapidly declined after ~3.5 billion years ago. But there are many gaps in our knowledge. Our understanding of the Moon’s impact history comes from (i) absolute age dates of rocks and soils brought back by the Apollo and Luna missions and (ii) understanding the relative age of when one impact crater formed compared with another (e.g., seeing when one crater occurred on top of another crater to build up a scale of what is older and what is younger).

Data from both sources have been combined to develop a lunar cratering curve – where the number of craters on a region of the Moon’s surface (as measured by crater counting like you are doing in the Moon Zoo crater survey task) is compared with the absolute rock age of that surface. A graphical representation of this curve is shown in Figure 2. As we have rocks from only nine known localities on the Moon, the scientific calibration of this curve is poor before ~4 billion years ago and for more recently after 3 Ga (see Figure 2). So, there are still some big questions about how many impacts have been hitting the Moon through time and if there has been one or more ‘spikes’ in the impact rate; when the Moon was pummelled by impacting projectiles in a very short period of time. One of these spikes is thought to have happened at ~3.9 Ga and is known as the lunar cataclysm (Figure 2). Other smaller spikes may also have occurred at other times in the Moon’s past.


Figure 2. The grey line indicates a possible lunar cratering chronology (number of impact craters ?1 km per km2 that have formed on the Moon’s surface at different times, based on a set ‘Size-Frequency Distribution’ for the projectiles). The black calibration points are derived from age dating samples of impact basins and lava flows (A = Apollo mission sampled lava flow, L = Luna mission sampled lava flows). The blue points are best guess calibration ages of impact craters and basin based on rock ages of material found at Apollo landing sites rather than in the crater itself. The red question marks refer to questions about the parts of the lunar impact curve where we have no calibration data at all. Credit: K. Joy adapted from the Stoffler et al. (2006) chapter in the New Views of the Moon book and from David Kring/LPI’s lunar impact flux diagram <http://www.lpi.usra.edu/nlsi/science/>

 

What has been causing such damage to the Moon and why do we care?
There are several different types of projectiles that have been hitting the Moon through time. These include:

  • ‘Primordial’ material left over from the formation of the Solar System – dust and small bodies that impacted the Moon very early in its history from 4.5 to 4 billion years ago (Ga).
  • Asteroids – Asteroidal projectiles originate from material that has migrated in from the asteroid belt and beyond. These types of projectiles are large enough to create cm to kilometre size impact craters. Asteroids include a range of varieties including types that have differentiated (i.e., formed a crust, a mantle and a core) and those that have never been melted and represent primitive (very ancient) Solar System material. If a fragment of an asteroid survives the impact event, this material is termed a meteorite. Meteorites that have come from primitive parent bodies are known as chondritic, and those from differentiated parent bodies are known as achondritic. Achondritic meteorites include a wide range of different types of stones including iron meteorites, martian meteorites, meteorites from the crusts of objects like the asteroid Vesta.
  • Comets – small icy rocky dusty bodies that orbit around the Sun and travel on orbits from the inner Solar System out into outer Solar System (known as short period comets). Some even travel outside of the Solar System’s elliptical plane (known as long period comets). Cometary projectiles are large enough to create cm to kilometre size impact craters on the Moon, but are not thought to easily survive entry through the Earth’s atmosphere.
  • Dust – the Solar System is full of dust sized particles left over from impacts between planets and asteroids. When dust and micrometeorids hit the Earth’s atmosphere they burn up and form bright streaks of light we call shooting stars. However, as the Moon does not have a protective atmosphere, small dust particles rain down straight onto the lunar surface – most are instantly melted and form glassy constructs in the lunar regolith, while others form small millimetre to micrometer sized impact crater pot holes on rocks and soil particles.

It is important to understand what sort of projectiles have been striking the Moon back through time as this provides us with information about dynamical processes in the Solar System. If we can understand what types of impactors caused a big spike in the lunar impact record at 3.9 Ga (e.g. the lunar cataclysm), then this knowledge might reveal information about what types of Solar System processes were occurring at this time. For example, some researchers have suggested that the lunar cataclysm was caused when a small planet or large asteroid broke up and its debris was thrown into an Earth-Moon crossing orbit. Other researchers have suggested that the cataclysm was caused when the orbits of the gas giants (Jupiter, Saturn etc.,) were suddenly altered, and that a dramatic change in orbit meant that large amounts of outer Solar System asteroids and comets were thrown into the inner Solar System, causing widespread damage to the asteroid belt and all inner Solar System planets. This hypothesis is known as the ‘Nice Model’ (named after Nice the city, not the term of affection!).  However, these hypotheses are at the moment just good guess work – and now we need further evidence to support, or refute such ideas.

How do we know what types of projectiles have been hitting the Moon in the past?
Well, we know what types of meteorites we find on Earth at the present day. We can classify collected stones and use this information to tell us about what types of asteroid parent bodies they come from. However, it is possible that the type of meteorites we find at the present day are not the same types that were hitting the Earth and Moon in the past.

Therefore, to understand the timing and sources of ancient bombardment on the Moon we must look at lunar samples returned by the Apollo and Luna missions, or that have been collected here on Earth as lunar meteorites (see blog here). Some of these rocks were formed in impact craters, and dating these impact rocks using radiometric dating techniques tells us when impacts to the Moon took place. There are then two methods used to work out what types of projectiles were hitting the Moon at these times:
(1)   To analyse the chemistry of the rock. There are two main groups of elements that help to reveal impactor source. Siderophile elements (e.g., Ni, Fe, Co, Ir, Au, Pt, Ru, Os, etc.,) can be used to trace if the projectile was an asteroid, and if so what type of asteroid it was. Light volatile elements like hydrogen and carbon species (e.g., H2O, CO, CO2, H2, CH4, HCN, N2, etc.,) help to reveal if the sample was formed, or affected, by a volatile-rich cometary impact (see Figure 3).
(2)   To locate and classify fragments of meteorites in the rocks themselves. Fragments that survive impact onto the Moon are very rare (Figure 4). Yet, several have been found in lunar rocks and soils. These samples are very important as they can be analysed and classified as originating from certain types of asteroid parent bodies.


Figure 3. Astronaut photograph of lunar soil sample from the Apollo 16 mission to the Moon. This soil, named 61220, has high levels of carbon and other volatile species and is thought by researchers at NASA’s Johnson Space Center to have been impacted by a comet. Credit: Image and further information about soil 61220 taken from LPI.


Figure 4. Photograph of a meteorite fragment that has been found on the Moon. This is Bench Crater meteorite that is from a carbonaceous chondrite parent asteroid body. The fragment is very small – about 5 × 3 mm in size. The dark opaque areas represent a fine grained matrix. The large brown mineral grains are attributed to clays (phyllosilicates) that have been converted to a ferromagnesian phase that is intermediate in composition to the minerals olivine and pyroxene (information credit Dr. Mike Zolensky). Credit: photograph of Bench Crater meteorite by K. Joy.

Different groups of researchers around the world are examining lunar rocks to search for evidence of the timing and sources of lunar impacts. We hope that these data will help us to not only better understand the geological history of the Moon, but to understand wider processes in the Solar System that have likely effected all rocky planets like the Earth, Mars, Venus and Mercury. This information will help us to understand the history of our own planet, and address how impacts may have affected the development and proliferation of life here on Earth throughout the past 4.5 billion years.

Few things to remember:

  • A projectile or an impactor is a term given to an object that strikes the Moon. This object may be a comet, an asteroid, or even dust
  • If a projectile is an asteroid, surviving fragments are called meteorites
  • If a projectile is smaller than ~50 m the object is often called a meteoroid and surviving fragments are also called meteorites
  • If a projectile is smaller than ~1 cm the object is called a micrometeoroid and surviving fragments are called micrometeorites
  • Is a projectile is dust sized, surviving fragments are called interplanetary or interstellar dust particles

Resources:

Types of impact crater shapes – the shape and structure of impact craters reveals what sizes meteorite or comet formed the crater

Understanding the number and size of impact events on the Moon at the present day – something that is very important for planning safe future lunar habitats and bases

General info about the postulated lunar cataclysm

L shaped dark ejecta

This week I found an image posted by ElisabethB which I think is worth another look.
It’s bright crater with dark L shaped ejecta.


http://www.moonzoo.org/examine/AMZ40013wv
Latitude: -2.69124°
Longitude: 342.478°
Sun Angle: -88.47°

As the crater is not very well placed here, it’s much better to take a look at the strip.

Do we have any more L shaped ejecta patterns?

Are they common?

How did this form?

The LROC strip can be found here http://wms.lroc.asu.edu/lroc/view_lroc/LRO-L-LROC-2-EDR-V1.0/M104634241LE and the crater is near to the top left.

Here is the forum thread with more comments.


Thomas J is a volunteer Moderator for the Moon Zoo forum

Another Look into Daguerre Crater with LROC

LROC Image

Apollo 16 Image

.

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.

Apollo 16 CSM

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:

http://clients.teksavvy.com/~iant/Various/InDaguerreFeO.jpg

“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

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.

Thanks,

Thomas J

Looking for Change: Crater Matching Apollo 15 versus LROC

Apollo 15 Image                                                                     LROC Image

Apollo lunar missions 15 – 17  carried onboard the orbiting command service module a sophisticated array of camera systems used for mapping the lunar surface from orbit.

Apollo 15 and Apollo 16 system arrangement

While reading, “APOLLO OVER THE MOON: A VIEW FROM ORBIT (NASA SP-362)” on page 123, I found a crater similar to an example Forum moderator Geoff posted for our Transient Lunar Phenomena (TLP) thread on Boulder Repellent.

AS15-9287 Panoramic (P) High Resolution  Click here for full image.

Lunar Atlas of Panoramic Camera Photographs and Image Catalog

The interesting name was given to this type of crater because of the open space in its center marked by a ring of boulders. To date we have not come across an example as good as the one posted on the TLP thread until now-  22.5° N / 34° E” in the Taurus mountains. With help from Forum moderater Jules and  Astrostu the Apollo 15 crater was tracked down on a LROC M126704350RE photo strip with a tantalizing partial view of the crater.  Jules was especially helpful in moving this project forward.

When a LROC photo strip is made showing the entire crater we hope to do a comparison of the crater center looking for change between the two versions as well as surveying craters and boulders in the surrounding area.  You are all invited to participate in the fun. Though not the superior resolution of LROC, the high resolution Apollo 15 version is very impressive.  Once you begin comparing the two versions of the crater, details in the Apollo 15 photograph begin to appear more clearly and you can see the details as smaller patterns but noticeable.  Downloading the Apollo 15 version and magnifying it with your photo viewer is a big help.  Also enhancing the photograph using a free online photo editing tool such as Sumo Paint allows one to modify the photograph with warmer colors (tan) to enhance boulders and craters.

Below is an example of an enhancement of the Apollo 15 crater center.  The annotated lines were made on Sumo Paint. The photograph resizing and hosting were performed at Photobucket. So, I moved the photograph back and forth as it was modified. The arrow points toward the large boulder on the crater rim (not shown).  The white radial lines move out from the approximate center touching boulders and areas closest in to give one perspective.  I also marked the circumference of the open center area. The red lines are possible alternative routes.

Visit the MZ Forum thread, “Crater matching – Apollo 15 v LROC” for more information on this project and how it evolved.  You can also participate in the investigation of two recently added Apollo 16 versus LROC photographs.


Tom128 is a regular contributor to the Moon Zoo Forum.

Splosh!


Latitude: 49.2394°
Longitude: 3.63271°

Back in June Moon Zoo forum member Toban posted this unusual looking crater in the Alpine Valley east of Plato from the LRO strip M104497175LE. Toban wondered if what we were seeing was “old” lava. He asked:

“Was the impact so deep, that this has “opened” the ground a long time ago?! I think there is no liquid under the moon surface… so maybe it is very old or it’s not lava…”

It reminded me of another unusual crater posted by Geoff a week earlier

which IreneAnt identified as “an impact into a not-completely-solidified melt sheet” and she also provided a link to a paper showing experimental impacts into viscous targets and noted that there were more examples of this type of crater in the same area (Aristarchus – strip M111904494RE.)

Alternatively could Toban’s crater be a very eroded crater or a “ghost” crater? Eroded craters have been worn and eroded by a history of micrometeorite impacts so that their original form is hard to make out. Ghost craters are craters which have subsequently been filled with lava leaving only a “ghost” of a rim visible when the sun is at a sufficiently low angle. Here are a couple of examples of ghost craters:

Prinz crater

wiki
. Stadius Crater

astrosurf.com

Toban thought this unlikely because his crater has a very definite unbroken ring structure with a clear boundary which has captured some of the boulders that have rolled down into the ring area.

Close up of Toban’s crater – the section around 10 o’clock

IreneAnt confirmed that Toban’s crater was another impact into viscous material and provided a link to another paper which describes laboratory experiments to study the morphologies of craters produced by impacts into various viscous materials using different impact velocities. IreneAnt draws our attention to Figure 4b of this paper which shows an impact into a clay-oil mixture producing a crater with no central peak and poorly defined rim topography. A similar type of crater, known as a “splosh crater” is much more common on Mars where the geology, history, atmosphere and gravity produce craters which are multi-lobed with splashed rather than rubbly ejecta. This type of Martian crater was formed when a meteorite hit an area rich enough in water to turn the impact site into runny mud. The lunar version, however, did not involve water but was formed because the impact site rocks had melted enough to behave like a viscous liquid. IreneAnt, therefore, suggests the term “melt splosh crater” to describe the lunar version to avoid confusion with the Martian water based splosh craters.

Although not quite the same thing the lunar versions were still formed more from a splash than a crash. Geoff found more examples of lunar viscous impact craters around King Crater on LROC strip M115529715LE.

These craters were formed when parts of the Moon were covered in molten lava and the splashes have been “frozen” as the lava cooled. So we should be able to find craters in various stages depending on the consistency of the lava impacted. Look out for them and post your finds in Toban’s thread.


Jules is a volunteer moderator for the Moon Zoo Forum.

Awesome Crater

Fra Mauro D crater

Fra Mauro D crater

This crater was found by user mercutin and posted in the Crater Questions thread on 4th November 2010.

This crater lip — in the mare south of Apollo 14 — can only be called “awesome” – mercutin

# ID: AMZ4000b8o
# Latitude: -4.79051°
# Longitude: 342.43°

I downloaded the LRO strip containing the crater and extracted the following image:


from strip: M102265088LC

The crater is called Fra Mauro D and is “a thermal anomaly crater” according to Moore et al 1980 (not Patrick Moore). It is about 5 km in diameter.

There is some very well defined dendritic filament-like debris flow on the crater wall, just what we are looking for in the TLP Project – The Landslides of Birt / Gullies project.

Unfortunately I wasn’t able to find an adjoining strip so it appears we only have half of this crater in LRO.

This NASA article has a picture of the Fra Mauro D crater: Apollo 14 Landing Site

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°
~

Impact melt in Aristarchus crater. Tom128
# ID: AMZ10036sv
# Latitude: 24.3744° / # Longitude: 312.405°
~

Interesting terrain in Aristarchus area. DJ_59
ID: AMZ300013p
Latitude: 23.9853° / Longitude: 312.908°
~

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

~

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