Thursday, September 30, 2010

The Great Wall of Aristarchus

Four days after First Quarter, as the Moon waxes Full, our first glimpse of Aristarchus and its namesake plateau comes before the ground-hugging terminator officially arrives with true dawn. This LROC WAC monochrome mosaic, swept up during four LRO orbital opportunities (in LRO orbits 2496-2499) January 10, 2010, allows us an overhead look at the High Wall contact, between plateau and mare, the most abrupt, angular transition between Oceanus Procellarum and anywhere around the plateau. As dawn briefly reaches over the horizon to this height the bow-shaped Wall often seems to hover by itself. As the smoky, colorful and wispy patterns here, including the bright inner slopes of Aristarchus proper (r) catch the sun, it's easy to see why this prominent near side landmark is the location most frequently cited for reports of "transient lunar phenomena" (TLP) [NASA/GSFC/Arizona State University].

Additional Reading:
LROC: Aristarchus - Up from the Depths
July 20, 2010

Extensive Copernicus ejecta

Extensive Copernicus ejecta
One of the geologic features that makes Copernicus crater special is its extensive, high-reflectance ejecta rays that extend across nearby mare and superpose (overlap) ejecta from other craters - Copernican ejecta extends more than 500 km from the impact site. In this high-Sun image, albedo differences are enhanced and the arrows indicate several "fingers" of ejecta and the direction of ejecta emplacement (away from Copernicus, which is to the southwest). 470 meter-wide field of view from LROC NAC observation M127050121L, LRO orbit 3857, April 27, 2010, spacecraft and camera slew 11.6° west from nadir, angle of incidence 30.4° at 47 centimeters per pixel resolution from 37.69 km [NASA/GSFC/Arizona State University].
Lillian Ostrach
LROC News System

Check out Wilhelms' Geologic History of the Moon for more information about Copernicus crater and the lunar geologic timescale.

Copernicus context for LROC NAC M127050121LE
LROC Wide Angle Camera (WAC) mosaic of monochrome (689 nm) observations of high illumination incidence angles captured over several sequential orbits in early January 2010. Familiar Copernicus (93 km diameter) is the result, overlaid on the lunar digital elevation model available through the Google Moon (v5) application. The arrow indicates the approximate position of the area shown at high resolution in the LROC Featured Image released September 30, 2010 and the blue boundary outlines the area captured in the LROC NAC observation seen in the corrected format below [NASA/GSFC/Arizona State University].
Copernicus (early LROC WAC color)
LROC Wide Angle Camera (WAC) visible to ultra-violet portrait of Copernicus in a 458 km-wide field of view, showing some degree of the extensive ejecta of the familiar Copernicus impact, a benchmark for dating lunar stratigraphy. LROC Featured Image, illustrating the post on that very subject written by principal investigator Mark Robinson, March 20, 2012 [NASA/GSFC/Arizona State University].
Discover the Copernicus ejecta deposits for yourself in the full LROC (corrected) Narrow Angle Camera frame, HERE.

Related Posts:
Central Peak of Copernicus Crater

Sunrise and sunset at Alpine Valley

Updated Thursday, September 30, 2010 1640 UT

The Alpine Valley at sunrise, from an outstanding mosaic of LROC Wide Angle Camera (WAC) observations swept up in successive orbital passes January 6, 2010. Processed by Maurice Collins, the work was posted as Lunar Picture of the Day (LPOD) September 30, 2010, and directly juxtaposed against one of the finer amateur observations offered by Jocelyn Sérot [NASA/GSFC/Arizona State University/LPOD/ILUJ].

The simulated view from the Vallis Alpes flyover, produced from SELENE-1 (Kaguya) Terrain Camera data in 2008; the 134 km length northeast from Mare Imbrium [JAXA/SELENE].

Additional Reading:
Really, Really Close-Up on the Alpine Valley
December 18, 2009

First Global Stereo-Imaging of the Moon
June 13, 2009

Wednesday, September 29, 2010

The smooth anomaly in Copernicus

With the exception of recent impacts (such as this one) into the floor material, much of the northwestern floor of Copernicus appears smooth and relatively featureless (upper right corner). This region on the crater floor appears similar to mare basalt flows, but studies show that volcanism has not shaped the landscape of Copernicus' interior. Instead, it is possible that a vast volume of melt was created during impact that cooled differentially across the crater floor, such that some areas appear smooth while others are hummocky. LROC NAC M135317661L; LRO orbit 5075, August 1, 2010, res. 50 cm; field of view = 260 meters [NASA/GSFC/Arizona State University].

Why is the full northeastern quarter of Copernicus' floor so relatively smooth? Increased access to the LROC Wide Angle Camera (WAC) observations is allowing a fresh look even at one of the most photographed craters on the Moon; LROC WAC Mosaic, January 8, 2010. [NASA/GSFC/Arizona State University].

Lillian Ostrach
LROC News System

With the exception of recent impacts (such as this one) into the floor material of Copernicus, much of the northwestern floor of Copernicus appears smooth and relatively featureless. This region on the crater floor appears similar to mare basalt flows, but studies show volcanism has not shaped the landscape of Copernicus' interior. Instead, it's possible a vast volume of melt was created at impact that cooled differentially across the crater floor such that some areas appear smooth while others are hummocky. LROC NAC M135317661L, frame width = 2.5 km [NASA/GSFC/Arizona State University].

West Copernicus, from a LROC Wide Angle Camera 60 meter/pixel monochrome (643nm) mosaic stitched from observations gathered during successive LRO orbits (2816-2820), February 4, 2010, and made possible by Ron Evans' LROC_WAC_Previewer (v.1.6) and Microsoft Research Image Composition Editor (ICE v.1.5) . The arrow indicates the approximate position of the NAC image at top [NASA/GSFC/Arizona State University].

How many blocky craters can you find in this smooth region on Copernicus' floor? Count them in the full LROC NAC image.

Related posts: Central Peak of Copernicus Crater

Copernicus and the lunar timescale

Updated Wednesday September 29, 2010 1039 UT

LROC Narrow Angle Camera view of the southern rim of Copernicus, down-slope to upper left. (Original-size view, HERE.) The fragmented material demarcates the rough edge of the crater rim. The surface texture is still sharp and crisp, indicating a relatively young age (note the boulder tracks) 470 meter width from LROC NAC observation M129418341L, LRO orbit 4206, May 25, 2010; alt. 39.41 km, res. 47.2 cm/pixel, phase angle = 57.53 [NASA/GSFC/Arizona State University].

Mark Robinson
Principal Investigator
Lunar Reconnaissance Orbiter Camera
Arizona State University

Copernicus crater played a key role as pioneering lunar geologists Gene Shoemaker and Robert Hackman unraveled the basic stratigraphy of the Moon fifty years ago. Stratigraphy is the science of determining relative ages of geologic materials by observing overlapping relationships between different geologic units. What is a unit? In the case of the Moon, the most basic geologic units include crater ejecta, mare basalt, volcanic ash, and the ancient highlands crust. Dr. Shoemaker and his colleagues noted that rays from different craters exhibited a range of albedos, from the very bright (Aristarchus crater) to the barely visible (Copernicus crater).

Copernicus (9.7°N, 340.0°E) in late afternoon. (Larger view) LROC Wide Angle Camera mosaic (LROC WAC Previewer (v.1.16), Microsoft ICE) from six LRO orbital passes (orbits 2466-2471) January 8, 2010 [NASA/GSFC/Arizona State University].

They correctly inferred rays fade with time, as they are sand blasted by micrometeorite impacts and exposed to the relentless effects of solar wind, cosmic rays: processes often referred to as “space weathering.” By tracing the path of rays, relative ages of many units can be easily determined.

LROC Wide Angle Camera mosaic showing Copernicus crater (L), Eratosthenes (R) along the southern rim of the vast Mare Imbrium impact basin. Ejecta of Copernicus cross over Eratosthenes, showing Copernicus is younger. Image field of view is ~400 km, north is up [NASA/GSFC/Arizona State University].

Just to the east of Copernicus crater is another key crater that in the lunar stratigraphic story revealed by Shoemaker and colleagues, Eratosthenes (58 km diameter). The two neighboring craters look very similar in terms of the freshness of morphological features (rim, walls, central peak), however Eratosthenes has no rays – they have completely faded into the background. The fact that Eratosthenes has no rays shows it is older than Copernicus, but the fact that its form is still sharp indicates that it is not so old that smaller impacts have worn it down. So Eratosthenes is "middle aged" in the lunar timescale. When the lunar timescale was unraveled, scientists had no samples from the Moon so they could not accurately determine the absolute ages of the geologic units they identified.

Gene Shoemaker (1928-1997) made many major contributions to planetary science. One of his most significant was deducing and proving that Meteor Crater in Arizona was formed as the result of an asteroid slamming into the Earth. Here he is seen enthusiastically telling the story of Meteor Crater to a new generation of planetary scientists while perched on the steep interior walls of the crater [Photo by Mark Robinson].

Later, material believed to be Copernicus ejecta was sampled by Apollo 12 astronauts, and these samples were radiometrically dated to be close to 800 million years old. 800 million years old is certainly an ancient age by terrestrial standards but is a relatively young age for the Moon. We have no samples from Eratosthenes and thus its absolute age is inferred from counts of smaller craters that have formed on its ejecta and interior. To this day, our knowledge of the ages of the Copernican and Eratosthenian units are poorly constrained. Obtaining samples of key areas within these two periods is a high priority amongst lunar scientists.

Farther down the terraced walls toward the crater floor, boulders of variable sizes are eroding out of the steep slopes. Many boulders are precipitously sticking out of the crater walls, such as the ~50 m boulder in the lower right. Erosion has completely freed some boulders, as evidenced by the boulder trail in the upper right. Downslope direction is toward the upper left, image field is 470 m [NASA/GSFC/Arizona State University].

As scientists learned more about the Moon from Lunar Orbiter and Apollo missions, the lunar timescale was refined. However, the Shoemaker and Hackman work still stands as our basic understanding of lunar stratigraphy. To learn more on lunar stratigraphy and other aspects of lunar geology, you can consult Don Wilhelm’s tome “The Geologic History of the Moon”. It is a serious read, but summarizes much of what we know about the Moon from a historical geology point of view. Certainly, the exciting results from LRO and three recent international missions (SELENE/Kaguya, Chang’E-1, and Chandrayaan-1) will provide many opportunities to revise past ideas! Perhaps Dr. Wilhelms will revise his masterpiece in the near future?

Explore the well-preserved impact landforms of Copernicus crater in the full NAC image and the WAC mosaic.

As an appropriate segue, a look at Shoemaker crater, once part of the stubbornly elusive, nearly completely shadowed terra incognitia near the Moon's South Pole. The South Pole LROC WAC mosaic below shows Shoemaker in visible light, while this 2009 image show the area, really for the first time, in star light, data collected by the Diviner instrument, also on-board LRO. Shoemaker became an even more fitting tribute to Dr. Shoemaker as final resting place for at least a portion of his remains which were deorbited here with Lunar Prospector, July 31, 1999. [NASA/GSFC/UCLA].

Tuesday, September 28, 2010

Lunar South Pole WAC mosaic

LROC Wide Angle Camera (WAC) mosaic of the lunar South Pole region, width ~600 km [NASA/GSFC/Arizona State University].

Mark Robinson
Principal Investigator
Lunar Reconnaissance Orbiter Camera
Arizona State University

The lunar South Pole is one of the most compelling places in the entire Solar System. This region of the Moon is important for both lunar scientists and engineers planning future human exploration. The towering massifs of the South Pole-Aitken Basin can be accessed, and these massifs contain impact melt that will allow scientists to unambiguously determine the age of this huge basin. Furthermore, permanently shadowed craters may harbor reservoirs of ices and other volatile compounds that could serve as a tremendously valuable resource for future explorers. Additionally, these volatile deposits could contain a priceless record of water composition dating back to the beginning of our Solar System, an incomparable dataset for astrobiology investigations. Finally, a few mountain peaks near the pole (just west and east of the rim Shackleton crater) are illuminated for extended periods of time, providing the near-constant solar power that would be required for the economical operation of a permanent lunar outpost.

LROC Wide Angle Camera South Pole mosaic showing locations of major craters. The impact site of the LCROSS spacecraft is marked with an "X". Full Mosaic width is ~600 km [NASA/GSFC/Arizona State University].

As LRO passes over the pole every two hours, the LROC WAC snaps an image, and over a month, images covering the entire polar region are captured (80°S to 90°S). This mosaic contains 288 images taken in one month; you can see where the month began and ended at about 90°E longitude (note how the lighting changed). The rim of Shackleton crater seems to be disjointed. However, if you look closely, you can see that the Sun came from opposite sides for portions of the mosaic, resulting in opposite sides of the crater's wall being illuminated in some images. As the mission progresses, the WAC captures the pole across the full range of seasons. More mosaics of the poles will be posted in the future.

Monday, September 27, 2010

Ejecta blanket in Van de Graaff

The pattern of ejecta from a young crater is still preserved on the floor of Van de Graaff. The variations in albedo indicate either different surface exposure times, grain sizes, or composition. Image is from NAC frame M110479695L with a width of 650 m and an incidence angle of 30° [NASA/GSFC/Arizona State University].

The small impact crater in Van de Graaff with it's "fresh" ejecta blanket, preserving a pattern that may predate the extinction of the dinosaurs or the Model A Ford. From LROC Narrow Angle Camera observation M110479695L, LRO orbit 1415, October 18, 2009; alt. 63.15 km [NASA/GSFC/Arizona State University].

Friday, September 24, 2010


Mons Rümker (40.8°N, 302.01°E) at dawn, means the Moon was nearly Full the night of December 28-29, 2009. The 72 km-wide volcanic heap lords it over the north-northwest Oceanus Procellarum and is never seen except in profile from Earth. Mosaic (by Microsoft ICE) from four LROC Wide Angle Camera observations (processed using LROC WAC Previewer v.1.6) over LRO orbits 2329-2332; avg. alt. 46.59 km., avg. res. 65.53 m, avg. LRO/Moon/Sun phase angle = 89.07° See larger view HERE [NASA/GSFC/Arizona State University]

Nearly a full lunar day later, late in a lunar afternoon, January 11, 2010, Rümker was fully illuminated perhaps for another 20 hours or so. Although, at middle latitudes north, areas behind the higher elevations have already fallen into long shadows as the Sun creeps down to within ten degrees of the southwest horizon. On Earth, the Moon is rising as a waning crescent before dawn. Another mosaic (by Microsoft ICE) from four LROC WAC passes in LRO orbits 2504-2507 (processed using LROC WAC Previewer v.1.6); avg. alt. 40.44 km., avg. res. 57.05 m, avg. LRO/Moon/Sun phase angle = 80.26° See larger view HERE [NASA/GSFC/Arizona State University].

Part of a spectacular HDTV view from Japan's Kaguya lunar orbiter in 2008 shows Rümker at dawn from 100 km polar orbit. [JAXA/NHK/SELENE].

Simulated view of Rümker from a point of view 8000 meters over the average -2200 meter elevation of this part of the Procellarum plain. The wide mound shows extensive signs of periodic intrusions of material piling over 900 meters above its surroundings, though most of the 72 km-wide feature is only 500 m high.

Thursday, September 23, 2010


In late afternoon. LROC Wide Angle Camera mosaic (LROC WAC Previewer, Microsoft ICE) from six consecutive passes during LRO orbits 2466-2471, January 8 & 9, 2010. (Closer view HERE. Images assembled with LROC_WAC_Image_Previewer, mosaic stitched with Microsoft ICE) [NASA/GSFC/Arizona State University]. [NASA/GSFC/Arizona State University].

Optically immature ("low OMAT") lunar surfaces

This crater in the floor of Van de Graaff has a high reflectance ejecta blanket compared to the surrounding low reflectance material. The contrast in albedo is due to the crater excavating "fresh" or "immature" material from underneath the surface. Next image field of view is 650 meters. LROC Narrow Angle Camera image M110472904R; 30° incidence angle [NASA/GSFC/Arizona State University].

- Sarah Braden
LROC News System

Ed. Note: Zooming in upon the LROC Narrow Angle Camera observation (M110472904R) affords up an opportunity to see what some have theorize to be two very different kinds of "optically immature" lunar surfaces, areas with "low OMAT." The higher albedo of rough material excavated by the subject crater is particularly highlighted in having apparently occurred directly in a dark lane, bifurcating brighter "swirl" patterns often coincident with local crustal magnetic anomalies on the Moon. In 900 million years the crater's fresh ejecta will have become reddened, darkened into the darker background. Meanwhile the surfaces inside the influence of the local magnetic field lines might well be little changed. Though such fields give no protection against micrometeorites or galactic cosmic rays, they have been shown elsewhere on the Moon to be intense enough to form mini-magnetospheres, deflecting the ever-present solar wind. LROC NAC observation swept up in LRO orbit 1414, October 18, 2009 [NASA/GSFC/Arizona State University].

Browse the full-resolution NAC image in our LROC Image Gallery!

Related posts:

Crater wall in Van de Graaff Constellation ROI
Ejecta from Van de Graaff Crater

Tuesday, September 21, 2010

Ejecta from Van de Graaff

Updated September 22, 2010 0021 UT

The texture of ejecta thrown from Van de Graaff Crater along the northern rim, seen from a low Sun angle in the NAC image (incidence angle = 72°). This subset of the NAC image M115177455R shows a field of view of roughly 1 km. LRO orbit 2107, December 11, 2009; alt. 62.75, res. 0.98 m/p [NASA/GSFC/Arizona State University].

Sarah Braden
LROC News System

Van de Graaff crater is located on the farside of the Moon south of Aitken crater, at about latitude -27.9, longitude 172.8. Two merged craters make up the formation known as Van de Graaff crater, named after the American physicist.

Unlike other merged craters on the Moon, there is no rim separating the two "sections" of the crater. A relatively strong magnetic field was detected near this crater by the Apollo 15 subsatellite magnetometer. This discovery was unusual for the lunar surface because the Moon does not currently have a global magnetic field like the Earth does. Also, Van de Graaff and the surrounding area also have slightly higher concentrations of thorium, a radioactive metal. Are the two observations related? To find out more about Van de Graaff crater, read our Apollo Image of the Week post.

Early LRO laser altimetry (LOLA) map of the Moon's far side show the 20 kilometer variance from mean global elevation, and the dominant 4 billion-old South Pole-Aitken basin. Van de Graaff, integral to the more ancient crater's rim, is indicated by an arrow [NASA/GSFC].

Van de Graaff crater. Mosaic of 18 LROC Wide Angle Camera passes, January 21, 2010; LRO orbits 2626 - 2634, res. averages 76 meters. "Look at the crater walls to see the unique grooved texture." (Closer view HERE. Image assembled with LROC_WAC_Image_Previewer Mosaic stitched with Microsoft ICE) [NASA/GSFC/Arizona State University].

Browse the full-resolution NAC image in our LROC Image Gallery!

(LOLA close-up of Van de Graaff, May 8, 2010)

Monday, September 20, 2010

Hansteen Alpha yields some of its secrets

Mons Hansteen (12.3°S, 309°8E), unusually bright for a remnant volcanic feature, is a 30 km-wide, 300 meter high mountain that, together with the inundated 48 km-wide Billy crater below, are telescopic landmarks of the southwest extremes of Oceanus Procellarum. Data from the Diviner instrument on board LRO, analyzed at Stony Brook University & UCLA, identified the southeast and southwest points of this feature among the surprisingly few silicate signatures found on the Moon. The LROC Wide Angle Camera swept up this 50 km-wide scene over the course of LRO orbits 2496 & 2497 on January 11, 2010. The mosaic was processed using Ron Evans' WAC Previewer [NASA/GSFC/Arizona State University].

Rachel Kaufman
National Geographic

If the moon were actually made of cheese, there'd be a new flavor of dairy for humans to sample.

Data from NASA's Lunar Reconnaissance Orbiter (LRO) have revealed a new type of rock on the lunar surface—which scientists say was spat up by a style of volcano never before seen on the moon.

Until now, scientists had believed the moon was made of two basic types of rock: dark basalt and light, calcium-rich feldspar. Both would have come from volcanoes spewing relatively runny basaltic lava.

But the new volcano type oozed thicker lava rich in silica over a light, arrowhead-shaped patch of the moon roughly 18 miles (30 kilometers) across, called Hansteen Alpha, the scientists say.

Read the full article, HERE.

The mosaic of LROC WAC observations M117819862 & M117826631 overlaid on the Google Earth lunar digital elevation model allows for a simulated view of the bright, low-profile landmark, from high over Billy crater.

Sunday, September 19, 2010

LOLA data improves the crater count

Updated September 20, 2010 0051 UT

Another Gap. Following up on a global crater count and mean elevation study of LRO laser altimetry (LOLA), spotlighted by NASA, Sept. 16, another conspicuous, surprisingly oblong gap in the distribution of >20 km craters appears in and around Mare Orientale [NASA/GSFC/LOLA/Brown/SVS].

A study of 5,185 lunar craters of similar size, their global distribution and how their interior elevations deviate from the Moon's global average appears to confirm work by Wilhelms, El Baz and others, published a half-century ago.

Amazingly, those earlier investigators, who improved existing maps of the near side and mapped what was still being learned about the wildly different far side, did not have the benefit of laser altimetry streaming down from the LOLA instrument on board the Lunar Reconnaissance Orbiter (LRO).

More amazing, the Moon's mean elevation, its average radius of 1737.5 kilometers, was far from accurately understood. The LAT package on board JAXA's Kaguya (SELENE-1) isolated the Moon's elusive center further, from within 2 km to within about 200 meters.

In comparison, the Brown University study authored James W. Head is rather like modern lunar instrumentation rated against Apollo guidance computers.

Originally, grid by grid, with slide rule geometry and calculus, plugging time and illumination angles into formula, crater counts of extraordinary accuracy were weaved together by patient investigators. Their published conclusions continue to be confirmed in the mining of laser data from LRO. But questions raised by them stubbornly remain unanswered by 21st century remote sensing. The Ground Truth is still irreplaceable

James W. Head of Brown University has performed a global census 5,185 lunar craters >20 km. in diameter. The study, published in Science, includes a global color-coded tally of the crater's interior elevations, showing deviation from the Moon's global mean "sea level" of 1737.5 km. Not surprisingly, a thinner population of such craters are found in and around familiar near side basins, reconfirming conclusions from long ago that the huge plains represent younger surfaces. (Of craters included in the Brown University census, green = mean global elevation; bluer = below, yellower = above.) [NASA/GSFC/LOLA/Brown/SVS]

So what are these data telling us, confirming theories and restating questions asked by the Light and Shadow slide rule guys of the Apollo era?

Broadly speaking, the Moon holds a reliable record of the history of the Solar System, a record largely lost to water, dynamic weather and plate tectonics on Earth. The Moon's obvious proximity shows this history is also the history of Earth, particularly the history of conditions in that part of the Solar System simultaneously occupied by both bodies.

And the Moon's surface tells a story writ large in bombardment, beginning a very long time ago with the large impactors, like the 4 billion year-old event that formed the 2,100 km-wide South Pole-Aitken basin or the 1290 km-wide Imbrium event that probably happened less than a few hundred million years later. All through the course of the past 4,500 million years, smaller but also respectable kinds of interlopers that punched out the craters in the Head census have continued to "encounter" the Moon with decreasing frequency.

If our dating of features on the Moon's surface is close to being correct, the fall-off in this more common kind of bombardment must have been fairly rapid. Otherwise, the 3.9 billion year-old near side basins, "only" a half-billion years or so after the Moon's magma ocean solidified, would be more punctuated with craters.

The evidence, particularly after studies of the Moon's far side literally entered the picture in 1959, hints that between the formation of SPA and the more familiar near side basins, a gradual decline in these "mid-sized" impacts may have reversed for a 150 to 200 million years before resuming its decline. This is the strongest evidence we have for what's become known as the Grand Bombardment, possibly a juggling of material perturbed as the outer planets, for some unknown reason, waltzed for several million years until stabilizing into their present orbits.

The presentation of the LOLA data study, prepared by the Science Visualization Studio (SVS) at NASA Goddard, was atypical in not including the classic near and far side panels; the two hemispheres shown side by side, centered on the 0° and 180° meridians. The SVS illustrations do include the separate panel above, centered on 90° and 900 frames from their animation. And the animation presents the 5,185 color-coded craters in a way that fancifully builds up gong from east to west as Moon rotates once around. This method does not allow for a view centered over any areas of interest other than the two equatorial slides. If you want to see the census results over Mare Orientale, for example, as at the head of this post, the area of interest falls behind before becoming fully populated [NASA/GSFC/LOLA/Brown/SVS].

Nevertheless, as the the Moon rotates, another second gap appears in the crater count, this time arguably in the the lunar highlands but hardly typical in composition, an oblong gap 2000 kilometers north to south and 1200 km wide centered on Mare Orientale.

Orientale was a late comer, slightly smaller and perhaps more energetic than the great basin-forming impacts of a billion years earlier. If dating methods are reliable, then the fall-off in >20 km-wide impact events had fallen to a trickle by the time of Orientale's formation, 3.1 billion years ago. Some studies hint the Orientale event was energetic enough to have caused an upwelling of molten material in the near side basins, the many ponds of mare material within South Pole-Aitken and elsewhere.

Additional Reading:
The Moon through LRO's eyes
Kelly Beatty
Sky & Telescope

Saturday, September 18, 2010

InOMN - 18 Septembre 2010

It's INTERNATIONAL OBSERVE the MOON NIGHT. If you've waited past Civil Twilight, the ancient angular momentum in Earth's rotation is catching up once again with our Moon. Waxing Gibbous, it appears much like it did 886 days ago, when Jocelyn Sérot captured this image. If it's been a while since you looked up, really looked up, AT the Moon, you may need to be reminded of some basic facts. If so, don't feel bad. Everyone tends to ignore beauty in their own backyard, and the Moon is patient. No one is poor who has such adornment framed by an apartment window, a wide meadow or a skyline, a soup line or a battlefield [LPOD/ILUJ/Jocelyn Sérot].

It's not Full, and there's no eclipse. What can you actually "observe" on the Moon, tonight?

Like Galileo, you can surprise yourself. Even modest magnification will delight the eye and allow a better view of the Moon's depth of field. You may need to remind yourself of the Moon's true distance. From limb to limb, it's diameter is equal to the distance from New York City to Las Vegas, for example, and it's almost thirty Earth-diameters away (a lot further than it looks).

Take a look at the richer field below, taken from within the mosaic above, specifically at the southwestern side, near the terminator. It's early morning on the Moon there, and because the shadows are long, some very subtle features that are ordinarily invisible at this distance (and sometimes harder to see up close) come into view now, and again briefly two weeks from now at local evening, when, unfortunately for most, the Moon will rise in the wee hours before dawn.

Like the Moon itself, there's more to the full-globe mosaic by Jocelyn Sérot than immediately meets the eye. The original combination of hundreds of exposures resulted in a detailed "observation," better than the best photographs taken through large telescopes just a few decades ago. Forget the easy stuff, the gestalt of huge mountains and rays for a moment and look again at the close-up, immediately above.

At dead center is a "ghost crater," where a ring of worn mountains are all that remain of a once-proud and craggy crater long ago overrun with molten material. Immediately to it's west is one of the Moon's many low-lying "domes."

Dome Kies Pi presents a very smooth low profile above the mare plain. It's best seen right now, while early morning shadows are long.

Need a better look? Thanks to the WAC Preview program written by Ron Evans, an outstanding contributor to Charles A. Wood's Lunar Picture of the Day forum, there are no better views available than this LROC Wide Angle Camera image. (Oh, I should remind you that LRO is "up there," too, by the way. By tomorrow afternoon, it will have orbited the Moon 5,700 times.)

That ghost crater is easy enough to cross-reference with the smaller-scale pictures, further up. But we're almost too close to really "see" this dome, looking through the LRO camera. The gentle rise of the dome, visible even in low power telescopes if you know where and when to look, is probably best "appreciated" from an aesthetics view, moving out into the backyard and tracing out the landmarks in finding it on the very face of the Moon [NASA/GSFC/Arizona State University].

Here's a look downward again only an orbit later, when LRO traveled a little more directly overhead. More accurately put, the Moon continued rotating under the LRO's polar orbit, allowing the spacecraft a complete data-picture of the Moon over time.

A little later that same month, here's the same area in late afternoon illumination. Can you spot Dome Kies Pi?

The deepest spot on the Moon nearly wasn't

The 10 km crater at bottom center, home of the Moon's lowest mean elevation (-9,020 meters - JAXA/SELENE, 2008 ) appears to have once nearly disappeared. Even though it's high in latitude, at 70 degrees south, it is not close enough to the pole to be permanently shadowed. It's a fairly normal crater for it's size, generally too small for a central peak with a rubble-lined middle interior and steep sloping inner rim. It's outer rim, however, disappeared one day, as it's host-crater's deep interior flooded with lava. LROC Wide Angle Camera observation M118639861M, LRO orbit 2617, January 20, 2010; alt. 53.95, res. 76.145, phase angle 85.12. Field of view = 32.3 km [NASA/GSFC/Arizona State University].

Not that anyone on Earth would have noticed. This "high-water" mark of molten lava, in this case probably oozing up from underground, was tucked away on the Moon's far side. If the "Man in the Moon" were a real face, the crater where the event took place was on the nape of the neck, where the spine meets the skull. In fact, because all the astronauts who ever visited there orbited much closer to the Moon's equator, no one has yet really seen this spot. Not that we haven't visited by proxy, plenty of times, since the Soviet Union managed to return the first photographs of the Moon's far side in 1959.

On Earth, multicellular life forms may have taken form by then. The raft of the melt that began flooding the host crater, 143 km Antoniadi (69.7°S, 188°E), came very close to spilling over it's north rim before it cooled. Because this flood event almost certainly happened long after after the formation of Antoniadi itself suggests it arose from the depths below Antoniadi, perhaps in the transfer of tremendous kinetic energy following the creation of Mare Orientale.

Studies just published, based on data returned from the Lunar Reconnaissance Orbiter, inform us this and the other "ponds" of mare-like material found in many place around there, near the center of the oldest, widest and deepest impact basin on the Moon - South Pole-Aitken (SPA) basin -is not composed of the "pristine magma" of the kind that may have once covered the entire Moon. The Moon's global "Magma Ocean" now appears to have "differentiated" as it cooled even before the basin-forming impact happened that formed SPA around 4 billion years ago, when no life we know of existed on Earth.

With no plate tectonics or the kinds of swift flowing water and wind we generally think of when we think of weather or climate on the Moon, our companion world holds fast to its ancient record of the history of the part of our star system also occupied by Earth. Because our record of the oldest life on Earth is mostly erased, its possible - even likely - that one day the oldest fossil record of life on Earth will be found on "terrestrial meteors" found on the Moon.

Thursday, September 16, 2010

Two major LRO milestones marked by LROC

The recent release of the LROC Wide Angle Camera mosaic of the Moon's eastern hemisphere inspired Moon watchers to pour over a view filled with objects both unfamiliar as well as features that, even if familiar, are impossible to see from the same angle from Earth. On the eastern edge of Mare Australe a feature briefly caught our attention. In the long shadows appeared what seemed to be a classic volcano, around 46.57°S, 113.89°E.

A Third Release of LROC images to the Planetary Data System (PDS), September 16, did not immediately provide any new Narrow Angle Camera observations of this "cone's crater," other than previously released close-ups of its high-angled slopes. But two newly Wide Angle Camera views from June 2010 did show the feature, most likely a worn crater perched on what remains of an equally worn ring of mountains surrounding the Australe basin. (Looks like good skiing in Narrow Angle Camera views.) - LROC Observation M130896509M, LRO orbit 4423, June 11, 2010; alt. 54.7 km, resolution 76.68 meters [NASA/GSFC/Arizona State University].

Mark Robinson
Principal Investigator
Lunar Reconnaissance Orbiter Camera
Arizona State University

The LROC Team delivers third archive volume to the PDS, more than 68,000 new images are now available, and September 16 marks the transition of the LRO mission from NASA's Exploration Systems Mission Directorate to NASA's Science Mission Directorate.

LROC Team Releases 3rd EDR and CDR Archive Volume

The third LROC release contains 68,992 EDR products, totaling 8.1 TBytes of images and ancillary files. The majority of the images were taken between March 16, 2010 to June 15, 2010. This release also contains images acquired on the dates: 2010-02-06, 2010-02-24, 2010-02-25, 2010-03-03, 2010-03-04, and 2010-03-05.

The 3rd CDR volume contains 69,091 CDR products, totaling 17.0 TBytes of images and ancillary files. The majority of images were taken between March 16, 2010 to June 15, 2010. There are also images taken on the dates: 2009-06-30 to 2009-12-31, 2010-02-06, 2010-02-24, 2010-02-25, 2010-03-03, 2010-03-04, and 2010-03-05 represented in the volume.

Total number of LROC EDR products released to date: 225,903 for a total 28.2 TBytes of images and ancillary files.

Total number of LROC CDR products released to date: 225,428, for a total of 55 TBytes of images and ancillary files.

Explore the new images on LROC's browse page.

ESMD to SMD Transition

September 16 marks the transition of the LRO mission from NASA's Exploration Systems Mission Directorate (ESMD) to NASA's Science Mission Directorate (SMD). Throughout the first phase of LRO's mission the spacecraft collected vast amounts of science data in support of NASA's exploration goals. The transition simply means that LRO science data will now support NASA's science goals. What does this transition mean in practice? For the most part the transition will be relatively seamless, with only a re-prioritization of special targeted observations. For example, the Constellation Regions of Interest will drop in priority and other high science value targets will have their priority raised.

The bottom line: LRO will continue to collect a bonanza of lunar science data.

LRO's LOLA reveals distinct populations in bombardment record and Diviner finds "no pristine lunar mantle," even within SPA

Reduced laser altimetry data from the LOLA instrument on-board the Lunar Reconnaissance Orbiter is presented in this topographic map of Mare Orientale, straddling the western limb and marking the border between the Moon's near and far side hemispheres. New studies using these data show the relatively late, dramatic Orientale "basin-forming impact" may have marked a more definitive change in the history of Earth-Moon bombardment than previously understood [NASA/GSFC/LOLA/Brown University].

LRO project management announced Thursday an investigation using data from the Lunar Reconnaissance Orbiter (LRO) laser altimeter (LOLA) have created the first-ever comprehensive catalog of large craters on the moon. One immediate result is the discovery of distinct periods and populations in the Moon's bombardment record.

Data from the LRO Diviner instrument used in two studies has uncovered a richer complexity to in the anorthosite-rich lunar highlands and, more surprisingly, no evidence of materials composed of the pristine lunar mantle Diviner was partly designed to detect.

The history of the Moon is also the history of Earth.

In a new study, Dr. James Head of Brown University describes results obtained from a detailed global topographic map of the moon created LOLA data.

"Our new LRO LOLA dataset shows the older highland impactor population can be clearly distinguished from a younger population in giant impact basins, inundated with solidified lava flows," Head writes. "The highlands have a greater density of large craters compared to smaller ones, implying that the earlier population of impactors had a proportionally greater number of large fragments than the population that characterizes the more recent lunar history."

The Moon, Mars, and Mercury all bear scars of ancient bombardment, impact craters hundreds or even thousands of kilometers across. Earth must have been subjected to this same assault as well.

Large impacts that occurred long after the advent of life on Earth appear to have resulted in Great Extinctions. The partially buried crater at Chicxulub, in the Yucatan, is from a 65 million years old impact widely believed to have led or contributed to the end of Age of Dinosaurs (and many other lifeforms, as well).

Scientists trying to reconstruct the bombardment history on Earth face difficulties because impact craters are relatively swiftly eroded by wind and water, or destroyed by plate tectonics. A rich record, however, is well-preserved on the Moon. The only source of significant erosion comes from other impacts, small and steady or large and less frequent.

"The moon is a Rosetta Stone for understanding the bombardment history of Earth," said Head. "Like Egypt's Rosetta Stone, the lunar record can be used to translate the hieroglyphics of a poorly preserved impact record on Earth."

Head and his team used the LOLA instrument on-board LRO to build a map highlighting lunar craters with unprecedented clarity.

LOLA sends laser pulses to the lunar surface, measures the interval needed for these pulses to reflect back to the spacecraft and then, with a very precise knowledge of the LRO's orbit, convert these data into increasingly more detailed topographic maps of the Moon, said Head.

Objects hitting the moon can be categorized into distinct populations. Each population has its own characteristics. Head also used LOLA maps to determine the times when these populations changed.

"Using the crater counts from within the basalt-inundated impact basins, the familiar "seas" of the Moon's near side, for example, and examining populations superposed upon older craters, we can date these transitions. The LRO LOLA impact crater database shows a transition occurred about the time of the Orientale impact basin forming event, about 3.8 billion years ago.

"The implication is this change in populations occurred around the same time as the large impact basins stopped forming, and this raises questions of whether or not these factors are related. The answers has implications for the earliest history of the inner solar system, including Earth," said Head.

Map showing locations (in purple) of anorthositic crust exhibiting compositional anomalies. The iron and magnesium-rich maria appear red while calcium-rich highlands appear blue green. The five anomalous silicic features are labeled. Full size figure 11, HERE. (Read the Diviner news release HERE) [Science].

In two other studies, researchers describe how data from the Diviner Lunar Radiometer Experiment instrument (Diviner) on LRO are showing that the geologic processes that forged the lunar surface were complex, also. Data revealed previously unseen compositional differences in the crustal highlands, and these have confirmed a presence of an anomalously silica-rich material in five distinct regions.

Every mineral, and therefore every rock, absorbs and emits energy with a unique spectral signature that can be measured to reveal its identity and formation mechanisms. For the first time LRO's Diviner instrument is providing scientists with global, high-resolution infrared maps of the moon, enabling the definitive identification of silicate minerals in the Moon's crust.

"Diviner is literally viewing the moon in a whole new light," said Benjamin Greenhagen of NASA’s Jet Propulsion Laboratory, and lead author of one of the Diviner papers.

Lunar geology can be roughly broken down into two categories – the anorthositic highlands, rich in calcium and aluminum, and basaltic maria, abundant in iron and magnesium. Both of these crustal rock types are deemed by geologists as 'primitive,' i.e., the direct result of crystallization from lunar mantle material, a partially molten layer beneath the crust.

Diviner observations have confirmed most lunar terrains have spectral signatures consistent with compositions that fall into these two broad categories, but also reveal the lunar highlands are far less homogeneous than previously believed.

In a wide range of terrains, Diviner reveals a presence of fine lunar surface material with compositions more sodium rich than typical anorthosite crust. The widespread nature of these "fines" hint there may have been variations in the chemistry and cooling rate of the "magma ocean" which is now thought to have formed the earliest lunar crust, or these could be the result of a secondary processing of the earliest lunar crust.

Most impressively, in several locations around the moon Diviner detects a presence of highly silicic minerals, like quartz, potassium-rich and sodium-rich feldspar - minerals only associated with highly evolved lithologies, rocks that have undergone extensive molten processing.

Detection of silicic minerals at certain locations is significant because these occur in areas previously shown to exhibit unusually high abundances of the element thorium, yet another proxy for highly evolved lithologies.

"The silicic features we've found on the moon are fundamentally different from the more typical basaltic mare and anorthositic highlands," said Timothy Glotch, assistant professor of geosciences at Stony Brook University in New York, and lead author of a second Diviner Science paper. "The fact that we see this composition in multiple geologic settings suggests that there may have been multiple processes producing these rocks."

Read "New types of rock found on Moon by researchers at Stony Brook," HERE.

No evidence for pristine lunar mantle material

Using data from the Diviner Lunar Radiometer, an instrument uniquely capable of identifying common lunar silicate minerals, scientists at Stony Brook University in New York and NASA’s Jet Propulsion Laboratory have found previously unseen compositional differences in the crustal highlands of the Moon, and have confirmed the presence of anomalously silica-rich material in five distinct regions. Diviner data superimposed on a Lunar Orbiter IV mosaic of Aristarchus crater. Red and orange colors indicate silicic compositions [NASA/GSFC/UCLA/Stony Brook].

One thing not apparent in the data is evidence for pristine lunar mantle material, which previous studies have suggested may be exposed at some places on the lunar surface. Such material, rich in iron and magnesium, would be readily detected by Diviner.

Even in the South Pole Aitken basin (SPA), the largest, oldest, and deepest impact crater yet to be identified on the moon, deep enough to have penetrated through the crust and into the mantle, presented no evidence of pristine mantle material.

It's reported likely if the impact that formed SPA or Apollo basins did excavate any mantle material, it has since mixed with crustal material from later impacts, inside and outside the 2100 km-wide SPA impact.

"The new Diviner data will help in selecting the appropriate landing sites for potential future robotic missions to return samples from SPA. We want to use these samples to date the SPA-forming impact and potentially study the lunar mantle, so it's important to use Diviner data to identify areas with minimal mixing," says Greenhagen.

NEXT step for ESA's first lunar lander

NEXT, ESA's lunar lander mission, is under development for a landing in the mountainous, heavily cratered terrain near lunar south pole, possibly in 2018. The ‘Phase-B1’ study is going on under the leadership of EADS-Astrium Bremen, where some key technologies will be developed and tested for the first time. The project will be presented to the ESA Ministerial Council in 2012 for final approval [ESA].

BERLIN - Sept. 16. What's being planned as the first soft landing in the Moon's south polar region took a step forward today when a further study contract was signed with EADS-Astrium in Berlin, Germany.

The mission aims to land in the mountainous and heavily cratered terrain of the lunar south pole in 2018. The region may be a prime location for future human explorers because it offers almost continuous sunlight for power and potential access to vital resources such as water-ice.

To reach the surface safely, the lander must precisely navigate its way to a mountain peak or crater rim, carefully avoiding boulders and steep slopes before gently setting down to take in one of the most spectacular views in the Solar System.

The Moon is a favored target for the human exploration missions outlined in the ‘Global Exploration Strategy’ (pdf) by 14 space agencies around the world. The strategy supports international space exploration and calls for further studies of the Moon and Mars – places where humans will one day live and work.

18-month effort begins in Berlin today

The contract was signed by Simonetta Di Pippo, ESA’s Director of Human Spaceflight, and Michael Menking of EADS-Astrium, in the presence of Peter Hintze, Parliamentary State Secretary in the German Federal Ministry of Economics and Technology.

"It is a great pleasure to see progress being made in Europe in the field of space exploration relying on key technologies developed for human spaceflight," affirmed Mrs Di Pippo.

"As we prepare ourselves to join the United States, Russia and Japan in the decision to utilize the International Space Station for 10 more years and beyond," she added, "we are preparing the next steps, and we are working to position Europe at the level of its competences and capabilities within the global exploration undertaking. With a strong and successful presence in low orbit, the Moon is the next natural goal on our common path to further destinations. Europe is actively and successfully present in these global projects, like ISS and exploration, which contribute to affirm our role as a modern, dynamic and innovation-driven continent."

"The proven capabilities of the Automated Transfer Vehicle as a technology demonstration are representative of Astrium’s skills and experience in automated rendezvous and docking procedures," said Dr. Menking, Astrium’s Senior Vice President Orbital Systems and Space Exploration.

"The concept of the new study is based on the technologies of ATV and this unique expertise will enable us to develop the key technologies; it would not be possible to envisage landing a robotic vehicle on the Moon without them."

From a design concept to hardware reality

European Space Agency Next lunar lander breaks a polar orbit a few hundred kilometers past perilune and begins its carefully timed and calculated Terminal Descent to the lunar surface, perhaps in 2018 [ESA].

The start of this ‘Phase-B1’ study is an important milestone because now, after the preliminary planning and feasibility studies, the mission’s design will be continued under the leadership of EADS-Astrium Bremen and some of the key technologies will be developed and tested for the first time.

The robotic lander will be designed down to the level of its various subsystems, such as propulsion and navigation. The contract will culminate in a ‘Preliminary System Requirements Review’ in 2012, which will provide the basis for the final design of the mission and lander.

The bright rim of 10 km-wide Shackleton crater, surrounding its permanently shadowed interior, supports the southern axis of the Moon's rotation. The pole itself presents a very small profile for a landing ellipse for a stationary lander. From "Lunar South Pole: Out of the Shadows," a mosaic of LROC Narrow Angle Camera frames M105824863L & R, LRO orbit 744, August 25, 2009 [NASA/GSFC/Arizona State University].

LRO transitions from exploration to science

Images of the Apollo 11 landing site from the Lunar Reconnaissance Orbiter clearly show the descent stage, the footprints of Armstrong & Aldrin and various equipment they deployed in July 1969 (including Buzz Aldrin's brief stroll to the edge of the crater east of the lunar module Eagle. Beyond the usefulness to science, LRO's first images of all six manned landing sites provide a poignant reminder of the manned lunar exploration legacy of the United States. Before the close-orbiting precision supporting the LRO Narrow Angle Camera operated by Arizona State University, this clear evidence of human activity on the Moon remained just beyond the camera resolutions of unmanned cameras in the decades since the Apollo orbital mapping cameras. At less than one half meter per pixel resolution, the LROC NAC clearly reveal not simply the LM descent stages of the six Apollo mission but lunar rover tracks and the foot paths of the twelve astronauts who explored the lunar surface between 1969 and 1972 [NASA/GSFC/ASU].

Michael Braukus

Nancy Neal Jones

The United States' Lunar Reconnaissance Orbiter (LRO) will complete the exploration phase of its mission on September 16, after a series of successes that added to the transformation of our understanding of Earth's nearest neighbor.

LRO completed a year-long exploration mission in a nearly circular polar orbit approximately 54 kilometers above the Moon's surface, comprehensively mapping the lunar surface in unprecedented detail, searching for resources and safe landing sites and measuring surface temperatures and radiation levels.

LRO's attentions will now turn from exploration objectives to scientific research as program management moves from NASA's Exploration Systems Mission Directorate (ESMD) to the Science Mission Directorate at the agency's headquarters in Washington.

"LRO has been an outstanding success," said Doug Cooke, associate administrator of the ESMD. "The spacecraft has performed brilliantly, and LRO science and engineering teams achieved all mission's objectives. The incredible data LRO gathered will provide discoveries about the moon for years to come."

LRO teams operating its instruments will continue forwarding data gathered during the last year to the Planetary Data System (PDS), which archives and distributes scientific information from NASA planetary missions, astronomical observations and laboratory measurements.

Thirty-five meter boulder among a sea of detail previously unseen in the two Constellation Regions of Interest on the Moon's Aristarchus Plateau. From LROC principal investigator Mark Robinson's report to the Third Annual NASA Lunar Science Institute Conference (Presentation - 17.5 mg PDF) [NASA/GSFC/Arizona State University].

By the time LRO achieves full mission success in March 2011, with data processed and released to the scientific community, it will have sent more information to the Planetary Data System than all previous planetary missions combined.

During its new phase of discovery, LRO will continue to map the moon for two to four more years.

"The official start of LRO's science phase should write a new and intriguing chapter in lunar research," said Ed Weiler, associate administrator for the Science Mission Directorate.

LRO was launched from Kennedy Space Center carrying a suite of seven instruments, June 18, 2009. After an initial Commissioning phase, LRO formally began a highly detailed survey of the Moon the following September.

Among results collected thus far from the mission are original observations of the Apollo landing sites; indications that permanently shadowed and nearby regions harbor water and hydrogen and other volatiles; observations that large areas in the permanently shadowed regions are colder than anywhere in the Solar System; detailed information about lunar terrain, and the first evidence of a globally distributed population of thrust faults, evidence the Moon has recently contracted and may still be shrinking.

Among other achievements, LRO captured high resolution pictures of Lunokhod 1, the first robotic lunar rover the Soviet Union used to explore withing Mare Imbrium in 1970, subsequently lost for nearly 40 years.

The rover was located to within 30 meters using the LROC Narrow Angle Camera, and this highly accurate position data enabled researchers to captured laser light bounced and clearly reflected back again from the French-built retro-reflector situated on the dormant Soviet lunar rover for the first time. This addition to the long incomplete laser reflector array left on the Moon by the U.S. and U.S.S.R. during the Apollo era should finally enable a precision in Earth-Moon distance measurements to within 3 cm, a target some cosmologists hope will aid in answering questions about "locality" of physical laws in the universe.

LRO also supported the Lunar Crater Observation and Sensing Satellite (LCROSS) impact, as the companion mission was sued to determined if the Moon's permanently shadowed craters harbor water ice, to select the Cabeus crater impact site and to observe the wispy fast expanding plume and to study an evolving temperature at the site soon after the LCROSS impact last October 9.

The previously eternally elusive comprehensive details of the "permanently darkened regions" inside and around the Moon's south pole, situated on the rim of 10 km-wide Shackleton crater. Though aspects of Shackleton interior were first unveiled by Japan's SELENE-1 (Kaguya), the suite of instruments on LRO are singularly equipped to eventually detail the entire Moon's surface, whether by Sun or starlight [Maria Zuber/NLSI/LOLA].

NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland built and will continue to manage LRO for the Exploration Systems Mission Directorate.

Michael Braukus -
Nancy Neal Jones -