Tag Archives: LRO

A minor rill on the Moon

Kathleen, a rill on the Moon
Click for full image.

Cool image time! The image above, reduced to post here, is a colorized digital terrain model produced from Lunar Reconnaissance Orbiter (LRO) data. On top of the original mosaic of photos the LRO science team has overlaid the elevation data obtained by LRO’s laser altimeter. It shows a tadpole shaped pit dubbed Kathleen, with its tail trailing off to the southeast. As they note:

Kathleen is a pyroclastic vent with a sinuous rille (colloquially known as Rima Mozart [Not IAU confirmed]) that extends from the southeast end of the vent. Rilles are large channels formed by sustained channelized lava flows. This vent is a great location to investigate ancient volcanism on the Moon.

The elevation data reveals one interesting feature: The lowest part of the vent pit is not at its western end, where one would think at first glance, based on the general dip that produced the rill flowing to the east. That the lowest point is at the widest section of the pit instead suggests that this pit no longer looks as it did when it was venting. In the almost four billion years since it is thought all volcanic activity here ceased, there has been plenty of time for the slow erosion processes on the Moon, caused by radiation, micrometeorites, and the solar wind, to partly fill this pit and round out its cliff walls.

The two overview maps below provide some context.
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A global map of rockfalls on the Moon

A global map of the rockfalls found on the Moon
Click for full resolution image.

A review of more than two million Lunar Reconnaissance Orbiter (LRO) images of the Moon has allowed scientists to compile the first global map of lunar rockfalls.

The map on the right comes from the paper. From the press release:

The result is a map of the lunar surface between 80 degrees northern and southern latitude that shows 136,610 rockfalls with diameters of more than two and a half meters. “For the first time, this map enables us to systematically analyze the occurrence and causes of rockfalls on another celestial body”, says Dr. Urs Mall from MPS.

Previously, scientists had assumed that lunar quakes in particular were responsible for the displacement of boulders. The new global map of rockfalls indicates that impacts from asteroids may play a much more important role. They are apparently – directly or indirectly – responsible for more than 80 percent of all observed rockfalls.

“Most of the rockfalls are found near crater walls,” says Prof. Dr. Simon Loew of ETH Zurich. Some of the boulders are displaced soon after the impact, others much later. The researchers hypothesize that impacts cause a network of cracks that extend in the underlying bedrock. Parts of the surface can thus become unstable even after very long periods of time.

Though the map suggests vaguely that these rockfalls are more scattered on the lunar farside and more concentrated in the mid-latitudes on the nearside, I suspect this is likely not so. If it is however it reveals something about the Moon that needs to be explained.

Dawn at the Moon’s North Pole

The rim of Aepinus Crater close to the Moon's north pole
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When dawn comes to the airless rough terrain of the Moon’s poles, it comes in fits and spurts. The floors of some craters never see it, while the high crater rims might have only a short time in darkness, their elevation high enough to keep the Sun above the horizon almost continuously. While there appear to be no places at the poles that have eternal daylight, there are places where night is short and infrequent.

The cool image to the right, cropped and reduced to post here, shows one such place close to the Moon’s north pole, the rim of Aepinus Crater. Taken by Lunar Reconnaissance Orbiter (LRO) on March 10, 2020, the illuminated area on this oblique image is about one by four miles in size. With dawn approaching this rim sees the Sun before the rest of the polar region, and remains illuminated long after the surrounding region has returned to darkness.

To get an idea of how small this one illuminated area is, below is a panorama showing the wide region around the rim.
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Triple impact on Moon

Impact craters Messier and Messier A on the Moon

Cool image time! A new image release from Lunar Reconnaissance Orbiter (LRO) takes a look at the impact process that created the crater Messier and its neighbor crater Messier A. The photo to the right, cropped to post here, shows both craters.

Take a close look at Messier A. It is actually a double crater itself. From the release:

Messier A crater, located in Mare Fecunditatis, presents an interesting puzzle. The main crater is beautifully preserved, with a solidified pond of impact melt resting in its floor. But there is another impact crater beneath and just to the west of Messier A. This more subdued and degraded impact crater clearly formed first.

Did these three craters happen as separate events. According to the data, it appears no. Instead, they might have all been part of a single rain of asteroids, all occurring in seconds.
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Crash site of Vikram found

Vikram impact point
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Using a mosaic of Lunar Reconnaissance Orbiter (LRO) images, citizen scientist Shanmuga Subramanian located on the Moon the debris and impact point for India’s Vikram lander that crashed there in September, an identification that has since been confirmed by LRO scientists.

The image on the right, reduced to post here, has been modified by the scientists to bring out the features that changed before and after the impact.

After receiving this tip the LROC team confirmed the identification by comparing before and after images. When the images for the first mosaic were acquired the impact point was poorly illuminated and thus not easily identifiable. Two subsequent image sequences were acquired on 14, 15 October and 11 November. The LROC team scoured the surrounding area in these new mosaics and found the impact site (70.8810°S, 22.7840°E, 834 m elevation) and associated debris field. The November mosaic had the best pixel scale (0.7 meter) and lighting conditions (72° incidence angle).

The debris first located by Shanmuga is about 750 meters northwest of the main crash site and was a single bright pixel identification in that first mosaic (1.3 meter pixels, 84° incidence angle). The November mosaic shows best the impact crater, ray and extensive debris field. The three largest pieces of debris are each about 2×2 pixels and cast a one pixel shadow.

No word yet on what this new information reveals about Vikram’s failure.

Lunar Reconnaissance Orbiter locates crashed Chinese orbiter

Before and after images showing Longjiang-2 impact site

Lunar Reconnaissance Orbiter (LRO) has located the Chinese microsat lunar orbiter Longjiang-2, which was sent to impact the Moon in August 2019 after it completed its technology demonstration mission.

The image above shows the before and after of the location, with the satellite’s remains visible as indicated by the arrow.

Through a careful comparison of pre-existing NAC images, the LROC team was able to locate a new impact crater (16.6956°N, 159.5170°E, ±10 meters), a distance of only 328 meters from the estimated site! The crater is 4 meters by 5 meters in diameter, with the long axis oriented southwest to northeast. Based on proximity to estimated crash coordinates and the crater size, we are fairly confident that this new crater formed as a result of the Longjiang-2 impact.

The picture of the impact site might not be very impressive, but remember, this satellite only weighed about a hundred pounds. The engineering however is impressive, on all counts. First, the Chinese built a tiny cubesat that reached lunar orbit and operated there for more than a year, during which it even took a picture of the Earth. Second, the engineering team of LRO was able to find this tiny impact site for such small spacecraft in less than four months.

Bhabha Crater at dawn

Central peaks of Bhabha Crater at dawn

Cool image time! The Lunar Reconnaissance Orbiter (LRO) science team have released a beautiful oblique image of Bhabha Crater, located on the Moon’s far side, taken just as dawn was breaking over the crater’s central peaks.

The image to the right is a section of that picture, showing the central peaks near the bottom with the western rim of the 50-mile-wide crater at the top. The giant shadows of those central peaks can be seen extending across the floor of the crater and against that western rim. The photograph was taken on August 28, 2019 from an altitude of about 45 miles. The area of the central peaks in daylight is estimated to be about nine miles across.

The LRO science team releases a new press release image about once every two weeks. I suspect that they hoped this release would have shown the location of India’s Vikram lander. As they are as yet unable to find it, they instead provided us this cool image instead.

If you go to the link you can use their viewer to view and explore this very very large image. For example, if you zoom into those central peaks you can actually see small boulders scattered across their rounded tops.

LRO’s 2nd attempt to find Vikram comes up empty

In their second attempt to find India’s failed lunar lander Vikram, the science team of Lunar Reconnaissance Orbiter (LRO) were unsuccessful in spotting it.

A project scientist of Nasa’s LRO mission confirmed that the space agency’s second attempt to locate Vikram had come up empty. “The Lunar Reconnaissance Orbiter imaged the area of the targeted Chandrayaan-2 Vikram landing site on October 14 but did not observe any evidence of the lander,” Noah Edward Petro, the project scientist told news agency PTI.

Petro explained that Nasa compared the images shot by the LRO on October 14 with an image of the same area before Vikram’s landing. Nasa used a technique that would help it spot any signs of impact on the lunar surface indicating Vikram’s possible location. However, the images revealed nothing.

“It is possible that Vikram is located in a shadow or outside of the search area. Because of the low latitude, approximately 70 degrees south, the area is never completely free of shadows,” John Keller, deputy project scientist of Nasa’s LRO mission, explained while speaking to news agency PTI.

Based on the data obtained during the landing attempt, it appeared that Vikram should have crashed within a relatively small target area. That they haven’t seen it yet suggests that it landed within a shadowed area that will take time for the Sun to reach, if ever, or that it is farther away that expected, which implies that during landing much more went wrong than presently believed.

LRO scientists release image of Vikram landing site

Overview of Vikram landing area
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The Lunar Reconnaissance Orbiter (LRO) science team yesterday released their high resolution image taken of the area where it is believed India’s lunar lander Vikram crashed.

The image to the right is not that image, but an oblique overview showing where that landing region is, the center of which is indicated by the white cross. Vikram was aiming for this flat region between the Simpelius N and Manzinus C craters.

In releasing the image, the scientists explained what they thought were the reasons they have so far failed to find Vikram.

We note that it was dusk when the landing area was imaged and thus large shadows covered much of the terrain, perhaps the Vikram lander is hiding in a shadow. The lighting will be favorable when LRO passes over the site in October and LROC will attempt to image the lander at that time.

You can explore the actual image at the link. It is quite large, though their viewer there allows you to zoom in and move about, inspecting each grid area very closely. As they note, there are a lot of shadowed areas.

LRO’s high resolution camera can see objects as small as Vikram, even if broke up somewhat on landing. The key for discovery will be timing. LRO will have to pass over at a time when the lander is not in shadow.

UPDATE: Below the fold is a side-by-side comparison of this region, with mid-day on the left and the dusk LRO image on the right, created by Rex Ridenoure of Ecliptic Enterprises.and graciously provided to me.
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LRO fails to spot Vikram on Moon

Despite successfully taking high resolution images of the area on the Moon where it is thought India’s Vikram crash-landed two weeks ago, the Lunar Reconnaissance Orbiter (LRO) science team has been unable to identify it in those images.

LRO’s Lunar Reconnaissance Orbiter Camera instrument, or LROC, imaged the intended south pole touchdown site for the lander, which is called Vikram, as planned yesterday (Sept. 17), Aviation Week’s Mark Carreau reported. But “long shadows in the area may be obscuring the silent lunar explorer,” Carreau wrote.

“It was near dusk as the region prepares to transition from a two-week lunar day to an equally long lunar night, so shadows covered much of the region, and Vikram may not be in the LROC’s field of view,” Carreau wrote, citing a NASA statement.

This means that they will simply have to try again during a later orbit. Eventually the lighting conditions will be right, and LRO will photograph Vikram.

LRO to image Vikram landing site next week

The Lunar Reconnaissance Orbiter (LRO) science team plans to take high resolution images of the Vikram landing site when the orbiter flies over that site on September 17, thus allowing them to release before and after images.

Noah Petro, LRO’s project scientist at NASA’s Goddard Space Flight Center, said that the orbiter is due to fly over the Vikram landing site Tuesday, Sept. 17. “Per NASA policy, all LRO data are publicly available,” Petro wrote in an email. “NASA will share any before and after flyover imagery of the area around the targeted Chandrayaan 2 Vikram lander landing site to support analysis by the Indian Space Research Organization.”

Officials with India’s space agency ISRO have said they have photographed Vikram with their orbiter, Chandrayaan-2, but they have not released these images as yet. Their have also been reports from India stating that their images suggest the lander is still in one piece, but these reports are not confirmed.

LRO’s images should clarify the situation. The images should also help tell us what exactly happened after Indian engineers lost contact with Vikram shortly before landing.

Golfing with boulders on the Moon

Boulder tracks on the Moon
Click for full resolution image.

Cool image time! The Lunar Reconnaissance Orbiter team this week released a beautiful image of boulder tracks rolling down the inside slope of 85-mile-wided Antoniadi crater on the far side of the Moon. The image above, cropped, reduced, and annotated to post here, shows these tracks.

The most obvious track is cool because the boulder almost made, as the scientists note, “a hole-in-one.”

Running from the outcrops to the rim of the partially buried crater is a track etched by a rolling boulder bigger than a bus. Perhaps a moonquake shook it loose. The boulder bounced and rolled toward the partially buried crater, plowing a path that is still visible through the loose material of the slope. When it reached the rim of the partially erased crater, its path curved and it slowed to a stop.

…Had it rolled just 75 meters more, the boulder might have plopped neatly into a 30-meter-diameter young impact crater on the floor of the partially erased crater.

The arrows I have added indicate two more less obvious boulder tracks. If you click on the full resolution image and zoom in you can also see another series of impressions in the middle of the photograph that look like a dotted line, suggesting they were left by a boulder bouncing down the slope.

The scattered of boulders in the floor of the small crater all likely came from the top of the big crater’s rim, which I show in the wider image below.

Wider image showing entire crater slope

The box indicates the location of the image above.

While many things over the eons could caused these boulders to roll (moonquakes, erosion from the solar wind, other nearby impacts), a close look at the ground surrounding them does not show tracks emanating from most, suggesting they have been there a very long time, long enough for the surface reworking caused by the solar wind to have smoothed those tracks out.

The Moon is airless and mostly dead. The solar wind is incredibly weak. Any changes caused by it will take a lot of time. Consider the time required to smooth out those tracks. The mind boggles.

Jackson Crater on the Moon’s far side

Jackson Crater

Central peaks of Jackson Crater

In celebration of the 50th anniversary of the Apollo 11 mission, let’s look at another cool Moon photograph. The Lunar Reconnaissance Orbiter (LRO) science team on July 19 released a new breath-taking oblique image of Jackson crater, located on the Moon’s far side. The image above, reduced significantly to post here, shows that photograph and the crater’s cluster of near-center peaks. From the caption:

East-to-west view of Jackson crater (44 miles diameter). Image was acquired when LRO was at an altitude of [69 miles] and the Sun was to the west of the crater (LROC was facing somewhat towards the Sun; phase angle 114 degrees). The central peak rises about [5900 feet] above the crater floor and the top of the crater rim in the background has more than [13,000 feet] relief relative to the floor. Image width is about [40 miles] and north is to the right

The white box indicates the area covered by the close-up to the right. From the article:

What is the composition of the crust from top to bottom? It is relatively easy to measure the surface, but what lies beneath the surface? On the Earth geologists can dig and drill deep into the crust. We do not have that luxury on the Moon, at least not yet! However, we can take advantage of natural drill holes in the crust – impact craters! When impacts occur they dig into the crust and the central peaks expose the deepest material. Jackson crater formed on what was rather uneven terrain: to the east of the crater the elevation is about +6000 meters and to the west about +3000 meters. The bottom of the crater sits at +1000 meters, and the material exposed in the central peak comes from more than 1000 meters deeper still. By studying the rocks exposed in the central peak we can get a glimpse of materials that have come up from five or more kilometers below the surface (>3 miles).

The black pile of giant boulders near the top of the close-up suggests molten material dredged up from deep below the surface. So do the many black boulders on the nearer mountain slopes.

Why this dark material does not cover the entire surface is not clear. The lighter and darker material indicates different materials and ages, but the specifics are not known, as yet.

The Untouched Moon

Montes Carpatus
Click for full image.

In celebration of Apollo 11: Continuing the theme of yesterday’s cool image, where I noted how little of the Moon we have really seen, today’s cool image gives us a breath-taking glimpse of one such untouched region, the Montes Carpatus region.

The photograph to the right, reduced to post here, was released by the Lunar Reconnaissance Orbiter (LRO) science team in March 2018. From the release:

Volcanic rocks are our best window to the deep interior of the Moon, and the Montes Carpatus has no shortage of volcanic landforms: lava flows, pyroclatic deposits, rilles, and more! Lavas are formed as the mantle begins to melt, so by sampling volcanic rocks of various ages from regions across the Moon scientists can reconstruct the range of compositions and processes over time. The Montes Carpatus formed as a result of the giant impact that formed the mighty Imbrium basin, the mountains are actually the raised rim of the basin.

Today is the 50th anniversary of the Apollo 11 landing. If you had told anyone involved in that mission that fifty years later no significant further manned exploration of the Moon had yet occurred, they would have scoffed.

It is a terrible condemnation of my generation, the generation that followed Apollo 11, that we did nothing grand like this. I challenge the generations today to reach higher, and do better.

The Taurus-Littrow valley

Taurus-Littrow Valley
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It might not be Apollo 11, but during this 50th anniversary week of that mission, why not look at where the last Apollo 17 crew landed, in the middle of the Taurus-Littrow valley, as shown on the right in a Lunar Reconnaissance Orbiter (LR) image released by the LRO science team in 2018.

The image illustrates how ambitious NASA had become by this last Apollo mission. The Apollo 11 site was chosen because it was flat with as few risks as possible. By Apollo 17, the Apollo engineers and astronauts were quite willing to drop the LM down into this valley between gigantic mountains. Granted, the valley was more than 400 miles wide, but considering the risks of every Apollo flight, the choice was daring to say the least.

Taurus-Littrow also has a cluster of craters believed to have been formed by material flung out from the formation of 86-kilometer-wide Tycho crater about 100 million years ago. Tycho is 2250 kilometers from Taurus-Littrow, but the impact that formed it was violent enough that it cast material far across the Moon.

Nor is this location the most spectacular on the Moon. In fact, considering that all the manned and unmanned missions in total have probably covered less ground than a New York cab driver does in a single day, we have seen almost nothing there.

A wave on the Moon

A lunar ejector blanket

Continuing this week’s celebration of the 50th anniversary of the Apollo 11 mission means we get to look at another cool image from the Moon. The photograph on the right, reduced to post here, was released by the Lunar Reconnaissance Orbiter (LRO) science team in 2016.

What are we looking at? At first glance it looks like a black & white photograph of The Wave in northern Arizona. What it is instead is the pattern of ejecta laid down across the surrounding terrain immediately after the impact that created relatively fresh Chaplygin Crater. From the website:

The delicate patterns of flow across, over, and down local topography clearly show that ejecta traveled as a ground hugging flow for great distances, rather than simply being tossed out on a ballistic trajectory. Very near the rim lies a dark, lacy, discontinuous crust of now frozen impact melt. Clearly this dark material is on top of the bright material so it was the very last material ejected from the crater.

Below the fold is a wider shot of the entire crater and its surrounding terrain, with the rectangle indicating the region covered by the close-up above The dark crust near the rim mentioned in the quote can clearly be seen.
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Weird lunar crater

Concentric crater in Apollo Basin on the Moon

In celebration of the 50th anniversary of the Apollo 11 mission, it is time for another cool image from the Moon. The photograph on the right, reduced to post here, was taken by Lunar Reconnaissance Orbiter (LRO) in 2013. It shows a weird crater with concentric features that is found within Apollo Basin, a large 334-mile-wide double-ringed impact feature in the southern hemisphere of the Moon’s far side.

Concentric craters have an inner rim whose formation mechanism is not yet entirely understood, but the concentric mounds may indicate that there is a discontinuity, such as layers with different strengths, in the subsurface excavated by the impact.

Or to put it more bluntly, they really have no idea why this crater ended up looking as it does.

A lunar crater wall two miles high

Giordano Bruno crater

Cool image time! Considering this week is the 50th anniversary of the Apollo 11 lunar landing, it seems appropriate to show some cool images from the Moon.

Today the Lunar Reconnaissance Orbiter (LRO) science team released a spectacular oblique image of Giordano Bruno crater. The image on the right is cropped and very significantly reduced to post here. It looks across the crater, with the near rim across the bottom of the picture and the wall of the far rim filling the photograph’s top half.

That wall is what makes this image cool. It is a cliff about 10,000 feet high, equaling almost two miles. Moreover, at its base is a now-solidified melt pool left over from the impact that made the crater.

Faster than a speeding bullet – or rather ten times faster than a speeding bullet – is a good starting point in terms of grasping the energy released in a typical impact event. That is, for a bullet approaching 2 kilometers in diameter! The pressure and heat that were released during the collision not only excavated a hole much larger than the impactor but also melted a tremendous amount the target rock. Melt was sprayed and sloshed on the forming crater walls where much of it flowed back, seeking the lowest point in the impact crater. From the LROC vantage point you can follow the path taken by impact melt as it flowed across the irregular floor, ponding in closed depressions, and some of it ultimately reaching the lowest point.

Below the fold is a much higher resolution section of this photograph, focused on the crater wall and the melt pool. I have still been forced to reduce the resolution somewhat to post it here. Along that cliff wall can be seen partial avalanches (the dark splotch near the center) as well boulder tracks with the boulders (probably larger than most houses) still visible as white spots at the wall’s base.

The scale here is difficult to imagine. This cliff wall is three times as high as The Abyss, the steepest single drop viewpoint along the south rim of the Grand Canyon.
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The travels of China’s Yutu-2 rover on the Moon

Yutu-2 and Chang'e-4
Click for full image.

The Lunar Reconnaissance Orbiter (LRO) science team today released images that track the travels of China’s lunar rover Yutu-2 from its landing on January 30, 2019 through June 3, covering the rover’s first six lunar days on the Moon.

The image to the right, cropped, reduced, and annotated to post here, shows the relative positions of both spacecraft as of June 3, 2019. In the release they also included a gif movie showing the progression of Yutu-2’s movements since landing.

Once a month, LRO passes over the Chang’e 4 landing site, allowing LROC to capture a new image. LROC has now imaged the site five times (since the landing) and observed Yutu-2 to have traveled a total of 186 meters (distance measured using the rover tracks). If you squint, portions of the rover tracks are visible as a dark path in the images from April, May, and possibly June.

table of Yutu-2's movements through June 2019

The LRO release also included a table showing the distance Yutu-2 has traveled with each lunar day, shown on the right. The table does not include the 23 meters (75 feet) the rover traveled on its sixth lunar day. My estimate yesterday that Yutu-2 was traveling an average of about a 100 feet per day, with the distances per day shrinking with time, seems largely correct. During the rover’s fourth and fifth lunar days it moved very little, either because they had found something very interesting they wanted to inspect more closely, or they were moving more cautiously as the rover’s life extended past its planned lifespan of three lunar days.

On the sixth day however they increased their travels again, suggesting that either they had finished the observations at the previous location, or they had gained more confidence in the rover’s staying power.

Future lunar colonies at Shackleton Crater at the Moon’s south pole

The rim of Shackleton Crater
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The Lunar Reconnaissance Orbiter (LRO) science team has released a new image of the rim of Shackleton Crater, reduced slightly in resolution to post here on the right. The Moon’s south pole is located on the crater’s rim near the top right of this image. As they note at the link, the interior of Shackleton never gets any sunlight, making it what scientists call a Permanently Shadowed Region (PSR), while a ridgeline running south to de Gerlache Crater gets sunlight 90% of the time.

An elevated ridge runs roughly between Shackleton and de Gerlache craters, and the relatively high elevation of this landscape means that some portions are illuminated up to 90% of the time, but nowhere is permanently illuminated. Future explorers could take advantage of this persistent illumination by setting up solar panels in several closely spaced locations providing nearly constant solar generated electricity.

The proximity to Permanently Shadowed Regions in and around Shackleton crater adds scientific value to this destination, as PSRs are often home to compounds such as water ice that are not found elsewhere on the Moon, but which contain clues to the history of of inner Solar System water and other volatile elements. A nearby, ready source of water-ice would also be of benefit to human surface activities, either as a consumable (air or water) or as spacecraft fuel.

Below is a more detailed map they provide showing this area, with the permanently shadowed regions shaded in blue. The green dot indicates the location of the south pole. The green arrows indicate regions in sunlight in the full image.

The region around Shackleton

Sadly, I expect we are looking at the locations of future Chinese and Indian lunar bases. Though the U.S. has done all the proper legwork to find out the exact locations to build a lunar base at Shackleton, our government has decided we will instead twiddle our thumbs in lunar orbit while other countries use our legwork to land and establish bases on the Moon itself.

New LRO pictures showing Beresheet impact site

The Lunar Reconnaissance Orbiter (LRO) science team yesterday released an image showing the impact site where the privately-built Israeli lunar lander Beresheet crashed onto the surface of the Moon on April 11, 2019.

“The cameras captured a dark smudge, about 10 meters wide, that indicates the point of impact,” said NASA. “The dark tone suggests a surface roughened by the hard landing, which is less reflective than a clean, smooth surface.”

The image released does not see the spacecraft but the surface evidence that an impact took place. Higher resolution images will be required to spot any surface wreckage.

The central peaks of Compton Crater

Central peaks of Compton Crater

Cool image time! The Lunar Reconnaissance Orbiter (LRO) science team today released a beautiful oblique image looking of the central peaks of Compton Crater, a far side crater with a floor that is fractured and is one of about 200 hundred such craters.

Today’s Featured Image highlights an floor-fractured crater (FFC) that could tell us much about the lunar crust. An asteroid or comet impact is thought to have excavated 146.6-kilometer-wide Compton crater about 3.85 billion years ago. Igneous intrusion or viscous relaxation — or perhaps both processes — subsequently produced branching fractures and small basalt plains within Compton crater. The latter are darker than their surroundings.

Unlike Copernicus Crater, the surface appears smooth. Go to the link and zoom in to see what I mean. All the fractures appear very large and filled in. Of course, that could be because of the image’s resolution, and that other images might show more details and pits.

I find the central peaks more intriguing, however. It appears that, following their formation they were hit by several bolides, one of which carved a gigantic deep hole into those peaks.

Yutu-2 heads west!

LRO images of Yutu-2 on the Moon
Click for full image.

A new image from Lunar Reconnaissance Orbiter (LRO) shows the path taken by the Chinese lunar rover Yutu-2 during its second lunar day of travel on the Moon. The LRO images on the right, cropped and reduced in resolution to show here, compares the rovers position at the start and end of February. The white arrow indicates the rover, with its Chang’e-4 lander visible between the three craters to the east. As noted by the LRO science team:

LRO passes over any given place on the Moon at least once every month (in the daylight), allowing the westward progress of the Yutu-2 rover to be seen. At the end of February, Yutu-2 was 69 meters from it’s home base, the Chang’e 4 lander; LROC images show Yutu-2 made 46 meters of westward progress during the month of February.

It appears from these orbital images that they are taking the smoothest route, with the fewest obstacles, away from the lander.

The travels of Moon’s scarce surface water

An analysis of data from one of Lunar Reconnaissance Orbiter’s (LRO) instruments have allowed scientists to map the movements of the scarce water on the lunar surface.

Up until the last decade or so, scientists thought the Moon was arid, with any water existing mainly as pockets of ice in permanently shaded craters near the poles. More recently, scientists have identified surface water in sparse populations of molecules bound to the lunar soil, or regolith. The amount and locations vary based on the time of day. This water is more common at higher latitudes and tends to hop around as the surface heats up.

…Water molecules remain tightly bound to the regolith until surface temperatures peak near lunar noon. Then, molecules thermally desorb and can bounce to a nearby location that is cold enough for the molecule to stick or populate the Moon’s extremely tenuous atmosphere, or “exosphere”, until temperatures drop and the molecules return to the surface.

The quantities we are talking about here are very tiny. This will not be the water that future settlers will depend on. Instead, it will be those pockets of ice in the permanently shaded craters.

New LRO image of Chang’e-4 and Yutu-2

Chang'e-4 and Yutu-2

The Lunar Reconnaissance Orbiter (LRO) science team has released its third and best image of the Chinese Chang’e-4 lander and Yutu-2 rover. The image on the right is a full resolution cropped section, with the lander on the bottom and the rover above and to the left.

Just after midnight (UTC) on 1 February 2019 LRO passed nearly overhead the Chang’e 4 landing site. From an altitude of 82 kilometers the LROC Narrow Angle Camera pixel scale was 0.85 meters (33 inches), allowing a sharper view of the lander and Yutu-2 rover. At the time the rover was 29 meters northwest of the lander, but the rover has likely moved since the image was acquired. This view has close to the smallest pixel size possible in the current LRO orbit. In the future however, LROC will continue to image the site as the lighting changes and the rover roves!

These future LRO images will allow us to track Yutu-2 and get an idea of its research, even if the Chinese do not release any information.

LRO spots Chinese lunar rover

Yutu-2 and Chang'e-4 on far side of Moon

The Lunar Reconnaissance Orbiter (LRO) science team has now released a second and closer image of Chang’e-4’s location on the far side of the Moon, which now also shows the nearby rover Yutu-2.

The two arrows in the image to the right, cropped to post here, show both. The rover is the dot on the right, with the lander to the left, both just beyond the arrow tips. Both are very small, with Yutu-2 for example only two pixels across. Still, with both you can see their shadows, equally small, to the left of both bright dots. With sunlight coming from the right, all the craters, which are recessed, have their shadows on the right. The spacecraft, sticking up from the surface, have shadows going to the the left.

As Yutu-2 continues its travels, LRO will likely take more images, allowing us to track it even if the Chinese provide limited information.

LRO photographs Chang’e-4 on lunar surface

Chang'e-4 on the lunar surface

The Lunar Reconnaissance Orbiter (LRO) science team has released a spectacular oblique image that shows Chang’e-4 on the floor of Von Kármán crater.

Four weeks later (30 January 2019), as LRO approached the crater from the east, it rolled 70° to the west to snap this spectacular view looking across the floor towards the west wall. Because LRO was 330 kilometers (205 miles) to the east of the landing site, the Chang’e 4 lander is only about two pixels across (bright spot between the two arrows), and the small rover is not detectable. The massive mountain range in the background is the west wall of Von Kármán crater, rising more than 3000 meters (9850 feet) above the floor.

The image on the right has been reduced to post here. If you click on it you can see a larger version, but you need to download a very large file at the above link to see it at full resolution.

Plato Crater on the Moon

Plato Crater's west rim

Cool image time! The Lunar Reconnaissance Orbiter (LRO) science team this week released a new high resolution image of the western rim of 63-mile-wide Plato Crater, located near the visible edge of the Moon’s near side. On the right is a slightly reduced version cropped to show the area of most interest.

Plato crater is prominent, yet from our vantage point on Earth we never truly see it as it is. That’s because it is located far enough north of the lunar equator (center latitude 51.62°N, center longitude 350.62°E) on the curving surface of the spherical Moon that it appears foreshortened. Plato is round like most other impact craters, but from Earth we see it as an oval aligned east to west.

A dark floor makes 101-kilometer-wide Plato crater stand out against a light-colored lunar highlands background. Plato crater is also prominent by association; the crater is located just north of 1145-kilometer-wide Mare Imbrium. A small part of this mare is visible at lower left in our Featured Image. Mare Imbrium is made up of many basalt layers laid down by violent volcanic episodes over a span of about 1.5 billion years. The basalts fill the Imbrium Basin, which a large asteroid or comet impact excavated about 3.85 billion years ago. When we look at a bright full Moon, round dark Mare Imbrium captures our gaze, then we see Plato crater, which is estimated to be about a hundred million years younger than the Imbrium Basin.

The western rim of Plato crater — visible on the east (right) side of our Featured Image — includes a 23.4-kilometer-wide slump block. The roughly triangular piece of rim broke free when an asteroid impact excavated Plato crater. Its eastern edge stands up to 1.4 kilometers above the crater’s dark floor. Part of the floor is visible in the image just above right center, east of the long shadow of the rim. [emphasis mine]

That block is thus 14.5 miles wide, and almost a mile high. I am trying to imagine what it was like when it broke off the rim and fell eastward into the crater floor. I am having trouble doing so.

Below is a image of the entire crater, with the area of the image above indicated by a white box. It shows clearly how this crater splashed into the basalt lava plain of Mare Imbrium.
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LRO pinpoints Chang’e-4 landing site

LRO pinpointing Chang'e-4's location on Moon

By referencing the footage released by China of Chang’e-4’s descent onto the Moon, the Lunar Reconnaissance Orbiter (LRO) team has been able to pinpoint exactly where the lander touched down. The image on the right has been reduced slightly. Click on it to see it in full resolution.

The largest nearby crater to the lander is estimated to be about 80 feet across.

Because the images were in December 2018 before the lander’s arrival, they do not show it. However, the LRO team now knows exactly where to look when they take new pictures in the next few weeks. Moreover, this will allow them to monitor Yutu-2’s travels as it roves the surface over the coming months.

Using LRO to find Chang’e-4

LRO image of Chang'e-4 landing area

The Lunar Reconnaissance Orbiter (LRO) science team has released a high resolution image from 2010 pinpointing the area on the floor of Von Kármán crater where Chang’e-4 landed. On the right is a reduced and partly annotated version.

They have not actually found the lander/rover, since this image was taken long ago before Chang’e-4 arrived. However, this image, combined with the Chang’e-4 landing approach image, tells us where the lander approximately landed. It also pinpoints where to look for it when LRO is next able to image this region, around the end of January.

By then, Yutu-2 will hopefully have traveled some distance from Chang’e-4, and LRO will be able to spot both on the surface.

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