Friday, December 9, 2011

LROC: Ejecta blanket geology

Unconsolidated material and impact melt (smoother areas) in the continuous ejecta blanket of Stevinus A, northeast of the bright nearside crater. LROC Narrow Angle Camera (NAC) observation M170227051L, orbit 10220, September 9, 2011, with a native resolution of 0.53 meters per pixel of a field of view 530 meters wide. View the full size original LROC Featured Image HERE [NASA/GSFC/Arizona State University].
Lillian Ostrach
LROC News System

Stevinus A (31.75°S, 51.55°E) is an 8 km diameter Copernican-aged crater located south of Mare Fecunditatis. Stevinus A is exciting to lunar geologists specializing in the study of impact craters because of its young age, but being young is not the only special thing about this impact crater. Dry debris flows create braided stream-like deposits down the crater walls. A small impact melt pond and subsequent slumped material are observed on the crater floor. Furthermore, taking a look outside the crater rim, the continuous ejecta blanket surrounding the crater is composed of intermingled unconsolidated ejecta (blocky material) and impact melt streamers.

LROC Wide Angle Camera mosaic of two observations covering the environs of Stevinus A. Of the Copernican Age, Stevinus A is geologically fascinating because of the degree of crater freshness, the presence of impact melt and very young dry debris flows inside the crater. LROC WAC observations M128942557C and M128949353C, orbits 4135 and 4136, May 19 2010; resolution 55.6 meters per pixel from 39.2 kilometers [NASA/GSFC/Arizona State University].

The opening image highlights the very quick nature of impact and subsequent ejecta emplacement. Sometimes, it is difficult to tell when ejecta and impact melt emplacement occurred. For example, was the unconsolidated material deposited first, followed by impact melt? Were melt and unconsolidated ejecta deposited simultaneously? In today's Featured Image, it is difficult to tell, especially because the impact melt streamers are not substantial flows as observed elsewhere on the Moon. However, based on observations of other Copernican-aged impact craters with impact melt, it is probable that the melt occurring in the Stevinus A ejecta blanket was emplaced after the ejecta blanket was emplaced - even if by only a few milliseconds. However, to be certain, scientists would need to complete a rigorous survey of these craters and make careful observations, attempting to discern the stratigraphic relationships between the unconsolidated ejecta and the impact melt.

Can you find additional evidence that supports (or refutes!) the observation that the impact melt was emplaced after the blocky portion of the ejecta blanket in the full LROC NAC image?

Related Posts:
Dry debris or liquid flow?
Brush Strokes of Ejecta
Ejecta Blanket
On the Shore of the Bay of Rainbows
Ray of boulders

Wednesday, December 7, 2011

On the floor of Green M

High-reflectance boulders interspersed among rubble eroding out from impact melt deposited on Green M crater floor. Illumination from right incidence angle 38.4° on a field of view 570 meters wide; LROC Narrow Angle Camera (NAC) observation M159080552L, orbit 8577, May 3, 2011 - resolution 0.62 meters per pixel from 60.09 kilometers. View the full size LROC Featured Image HERE [NASA/GSFC/Arizona State University].
Lillian Ostrach
LROC News System

Impact craters come in all sizes and morphologies due to different impacting conditions (e.g., impactor velocity, impactor material, angle of impact) and target materials (e.g., rock type, coherent or fragmented material). Green M (0.336°N, 133.117°E, southeast of Mendeleev crater) is a 35 km diameter crater with beautiful wall slumps, several terraces, and ponded impact melt deposits on the crater floor. In the opening image, both impact melt and fractured target material are visible. The two high-reflectance, fractured blocks are approximately 25 m wide and about 40 m in length; about the width of two school buses and the length of three school buses. These blocks are partially covered by a thin layer of impact melt or regolith, so it has been some time since these multiple-schoolbus-sized rocks last moved substantially (probably seconds after impact), unlike the likely more-recent rolling boulders observed elsewhere.

Full 5.8 km width of both left and right frames of LROC NAC M159080552L, reduced one-third from 4 meters per pixel resolution as viewed using LROC QuickMap, HERE. Square shows approximate field of view seen in Featured Image further above[NASA/GSFC/Arizona State University].
Forty kilometer wide view of Green M, with the location of the Featured Image (0.426°N, 133.236°E) indicated by arrow. Range of elevations above global mean derived from LROC QuickMap. Image LROC Wide Angle Camera (WAC) M149648971CE (643 nm); orbit 7187, January 14, 2011. Illumination is from the west at an incidence angle of 72.33° Resolution 79.22 meters per pixel from 58.26 km [NASA/GSFC/Arizona State University].

A thin layer of regolith does not completely obscure the irregular shallow depressions, or negative relief features, surrounding the high-reflectance boulders or the much smaller (<10 m) rocks eroding nearby. These depressions probably represent collapsed pockets in the impact melt sheet, similar to those observed in the King crater impact melt. However, enough time has passed to accumulate a layer of regolith that obscures what was originally a distinct rim, smoothing the surroundings while also enhancing small rock erosion - due to micrometeorite impacts - on the melt sheet over time.

What other interactions between target material and impact melt can you find in the full LROC NAC image? Can you find evidence for additional negative relief features or pits in the impact melt deposit?

Related Posts:
Impact melt in Anaxagoras crater
Ejecta in Tycho crater
The Chicken or the Egg?

Oblong Roche V

The boundary between the flooded crater floor and crater wall of Roche V  wall is subtle, except for locations where a distinct pinch represents the contact between units. LROC Narrow Angle Camera (NAC) observation M159100166R, orbit 8580, May 3, 2011; incidence angle 53.76° and reduced from a resolution of 0.59 meters per pixel from 57.3 kilometers. View the original, full size 590 meter wide field of view LROC Featured Image HERE [NASA/GSFC/Arizona State University].
Lillian Ostrach
LROC News System

Roche V (38.86°S, 129.62°E) is one of five satellite craters associated with Roche crater. Compared to its siblings, Roche V is the ugly duckling of the bunch: it has an oblong, irregular shape, floor fractures, and mare fill. But, similar to the ugly duckling in the story, the geologic features that stand out and catch our attention make this 29 km diameter crater quite special indeed. The irregular shape tells us something about the crater formation, probably because the impactor hit the lunar surface at a highly oblique angle. But maybe more exciting is the flooded mare material in the crater, along with both linear and arcuate fractures. There are many floor fractured craters on the Moon, but most of them are much larger than Roche V (for example, Gassendi is 110 km in diameter). The cause of fractures in these larger craters remains poorly understood, but scientists do know that the floors of these craters are uplifted and many contain smooth deposits of basalt. Given the size difference between Roche V and these larger craters, can we explain the geology of the Roche V crater floor?

LROC Wide Angel Camera (WAC) observation M115462620CE, (604 nm) image of satellite crater Roche V. Roche, the parent crater, is located to the southeast of this view. Arrow marks location of pinch contact discussed above. LRO orbit 2149, incidence angle 77.07° with a resolution of 85.7 meters per pixel from 61 kilometers [NASA/GSFC/Arizona State University].
Taking a look at the WAC image, there is a striking difference between the fractures in Roche V and those observed in other floor fractured craters, such as Atlas (87 km diameter). The fractures in Atlas and other floor fractured craters are large, somewhat resembling linear rilles in appearance. However, the fractures in Roche V are not as sharply defined and appear visually shallow compared to those observed in Atlas. The fractured and rougher mare fill (including the location of today's Featured Image) has a higher albedo than the smooth mare. Maybe the Roche V mare fill is partially covered by high albedo ejecta from a nearby recent impact; can you find any craters with high albedo ejecta blankets using the LROC WMS viewer?

The surface features of the floor material in Roche V are visually similar to the surface of a cornstarch and water mixture in a bowl as it dries. The material that lapped up on the sides of the crater stuck there as the lava cooled, but as the lava cooled it experienced a small volume change and shrank. The fractures observed may be the result of cooling within the lava pond. Much of the contact between crater wall and floor-fill is currently blurred and smoothed due to post-impact modification and regolith formation and at the NAC scale are very difficult to discern, but there are still a few distinct contacts visible in LROC NAC images.

What do you think - what formed these fractures? Take a look in the full LROC NAC image!

Related Posts:
The fractured floor of Compton
Alphonsus crater mantled floor fracture

Tuesday, December 6, 2011

CME's could 'sandblast' the Moon

Dust off: Images from computer simulations of the lunar calcium exosphere during a Coronal Mass Ejection (CME-left) and slow solar wind (SW-right) condition. Red and yellow indicate a relatively high abundance of calcium ions and blue, purple, and black indicate a low abundance. A CME produces a much denser exosphere than the slow solar wind. View movie of simulation HERE [NASA/Johns Hopkins-APL].
Bill Steigerwald
NASA GSFC


Solar storms and associated Coronal Mass Ejections (CMEs) can significantly erode the lunar surface according to a new set of computer simulations by NASA scientists. In addition to removing a surprisingly large amount of material from the lunar surface, this could be a major method of atmospheric loss for planets like Mars that are unprotected by a global magnetic field.

The research is being led by Rosemary Killen at NASA's Goddard Space Flight Center, Greenbelt, Md., as part of the Dynamic Response of the Environment At the Moon (DREAM) team within the NASA Lunar Science Institute.

CMEs are basically an intense gust of the normal solar wind, a diffuse stream of electrically conductive gas called plasma that's blown outward from the surface of the Sun into space. A strong CME may contain around a billion tons of plasma moving at up to a million miles per hour in a cloud many times the size of Earth.

The moon has just the barest wisp of an atmosphere, technically called an exosphere because it is so tenuous, which leaves it vulnerable to CME effects. The plasma from CMEs impacts the lunar surface, and atoms from the surface are ejected in a process called "sputtering."

"We found that when this massive cloud of plasma strikes the moon, it acts like a sandblaster and easily removes volatile material from the surface," said William Farrell, DREAM team lead at NASA Goddard. "The model predicts 100 to 200 tons of lunar material – the equivalent of 10 dump truck loads – could be stripped off the lunar surface during the typical 2-day passage of a CME."

This is the first time researchers have attempted to predict the effects of a CME on the moon. "Connecting various models together to mimic conditions during solar storms is a major goal of the DREAM project," says Farrell.

Read the NASA/GSFC News Release, HERE.

Dream Team - NASA/GSFC/NLSI

Saturday, December 3, 2011

"Boy, that sure looks like Luna 9!"

Fig. 1  Idealized Google Earth icon of Luna 9, the first soft-landing on the Moon (the first soft-landing anywhere other than Earth), February 3, 1966. The cartoon Russian spacecraft is pinpointed more than 30 kilometers northeast (8.0°N, 296.0°E) of an 'official' landing site (7.08°N, 295.63°E) because investigators say the 'official' coordinates place the lander well beyond the eastern rise, at left on the horizon above. That location doesn't appear to match the landscape seen in the panoramas returned to Earth. The object identified as a likely candidate, at 7.153°N, 295.630°, is less than 2.8 km north of the official coordinates, but at a notably higher elevation on that same rize, perhaps where fewer obstructions are to be found on the local horizon [NASA/USGS/JAXA/Google].
Joel Raupe
Lunar Pioneer

The problems encountered by the Russian Federation after the launch of Fobos-Grunt on November 9, when compared with the apparent ease NASA is experiencing, thus far, in getting Curiosity through the present Martian launch window, might tempt fools to dismiss Russia's interplanetary skill. Russian morale might be threatened but we're reminded yet again that Space is relentlessly intolerant of cutting corners or under-funding. The Great Galactic Ghoul, that cosmic gremlin supposedly spoiling to ruin Mars and Moon missions alike, spends most of its time here on Earth.

Off-planet, when Institutional Memory is applied efficiently, the Russians are a match for anyone.

Friday, December 2 is the 40th Anniversary of the first soft-landing on Mars, and Russia's Mars 3 lander was successful, though the lander operated on the surface only 20 seconds, back in 1971. Saturday, December 3 is the 12th Anniversary of the loss of America's Mars Polar Lander in 1999. Thus, the success of Curiosity is by no means a sure thing. When space exploration begins to look too easy disaster waits patiently at the door.

A planned Russian return to the lunar
surface may ultimately benefit from a post-
Fobos-Grunt shakeout
[RussianSpaceWeb].
The first vehicle soft-landed on the Moon (and the last one landed there, a decade later) were strictly Made in Russia. Embarrassing and often tragic, spectacular failure also often fuels political will, without which governments accomplish nothing.  After a latter-day purge of Russia's unmanned mission contractor NPO Lavochkin, the legacy of Fobos-Grunt may help guarantee eventual success for Luna-Grunt and the other lunar missions Russia has in the works.

If all goes well, beginning next month, the United States will support five spacecraft exploring the Moon simultaneously, the most prominent among them the record-smashing LRO. Following decades of a near total neglect of its hard-won and expensive lunar legacy, America owes a revival of interest in Earth's Moon directly to the loss of Columbia in 2003.

An early priority for LRO was a survey of human artifacts on the Moon. Delivering spectacularly on that assignment were Mark Robinson, principle investigator for the Lunar Reconnaissance Orbiter Camera (LROC), together with his team at Arizona State University. Their most newsworthy success, quite naturally, were many high resolution history-making photographs of the relics and footprints from the Apollo program.

Fig. 2  Planitia Descentus - Latin for Plain of Descent, a human distinction for an otherwise indistinct borderland along the western edge of Oceanus Procellarum, where Luna 9 came to a tilted stop February 3, 1966.  The yellow dot on the rise at center bottom on both maps makes the location of an object that could be Luna 9. These comparative maps of the same 14,300 square kilometer area (centered near 8.48°N, 64.47°W) are (top) LROC WAC DTM  juxtaposed with (bottom) LROC WAC mosaic, each from LROC/ASU QuickMap (250 m/pp resolution). [NASA/GSFC/Arizona State University].
A steady stream of LROC Narrow Angle Camera (NAC) views were released during the LRO Nominal Mission revisiting the remains of a host of U.S. and Soviet spacecraft, both impact craters and the intact sentinel spacecraft themselves following hundreds of lunar days and nights. Each of these Featured Images released by LROC has fired the imagination while calibrating and confirming some very old, often incomplete sets of data.

Finding Lunokhod 1 (38.316°N, 324.996°E), for example, was an overdue accomplishment. It was the first robotic rover on another world, equipped with a laser range reflector that had eluded detection for decades. Its addition to the passive network of reflectors set up by Apollo 11, 14 and 15, together with its French-built twin on Lunokhod 2 allowed the measuring of the Earth-Moon distance to within 3 mm, the missing tolerance needed to test whether a range of physical laws were exclusive to our neighborhood in the universe.

A compendium of LRO's definitive findings, LROC Coordinates of Robotic Spacecraft, put together by Samuel Lawrence at ASU, was released April 5, 2010.

Though the list has not been updated since, it's still spectacular. For the first time, for example, anyone with an Internet connection can see precisely what happened when the third stage of the Saturn V that pushed Apollo 13 around the Moon impacted with the lunar surface. And planetary scientists have a precise date on a fresh impact crater on the Moon, as well; a standard useful for dating optical maturity and space weathering. We no longer have to imagine if the footprints are still there and decades of doubters can precisely see for themselves how the astronaut's surface photography matches the landscapes as seen only 45 (and more recently 25) kilometers away.

Still, the table put together by Lawrence can't yet be comprehensive.

A search for the place where Luna 2 became the first man-made object to impact another world in 1959, for example, is fraught with uncertainty. Those official coordinates are necessarily wide of mark, if only because the precise location of the Moon itself, and its surface, would never again be less well understood than before the Russian measured the time of impact for Luna 2.

A search for Luna 2 using those rounded-off coordinates brings the investigator west of Autolycus, to a 22 square kilometer area where there are at least two, perhaps three, fresh craters with the proper wispy signatures. One of them shows signs of a unique debris field, perhaps dotted with a cluster of the impact-resistant Soviet flag-engraved metal balls reportedly loaded on Luna-2. A surface expedition will be needed, in other words. As amazing as it is, however, even the LROC Narrow Angle Cameras have their limits.

At the very edge of those limits is Luna 9, the 99 kg.lander the Soviets succeeded in soft-landing on the Moon on February 3, 1966. In Multiple NAC footprints covering the target area uploaded to the Planetary Data System, even by April 2010, it was easy to see the LROC team had already earnestly tried to find that historic relic. But Luna 9 wasn't on the list put together by Lawrence.

Fig. 3  A closer look at the Plain of Descent.  The rectangle matches a 2.5 km-wide cross-section of LROC NAC observation M137970706R, the area seen in Figure 6a, below. The small white dot marks a spot less than a kilometer south of the rectangle, the official Luna 9 landing site, and the white dot inside the rectangle marks the location of an "object of interest," something that seems to be a Luna 9, in the two NAC observations detailed below.  The 'mid-morning' view above is a 41-km-wide field of view taken from LROC Wide Angle Camera (WAC) observation M160376850C (604 nm), LRO orbit 8769, May 18, 2011; incidence angle 55.42° with a resolution of 57.55 meters per pixel, from an altitude of 40.49 km [NASA/GSFC/Arizona State University].

As noted expert on lunar artifacts Phil Stooke of the University of Western Ontario put it, finding the very first vehicle soft-landed on the Moon was "problematic," even with the proven sensitivity of the twin LROC Narrow Angle Cameras. 

There is lingering dispute about the true landing site, though the central difficulty in finding Luna 9 is probably the small spacecraft's low profile. Its instrument housing is barely at the half-meter limit to the LROC NAC Nominal Mission resolution. And, because discussing Luna 9 without seeing its mission in the context of the Cold War would be incomplete, a brief comparison with Surveyor, its very real competition, is necessary.

The Russians beat Americans to the Moon in 1966 by only five months. Samuel Lawrence had already written up and released LROC's first views of "Surveyor 1 - America's first soft lunar landing," on September 30, 2009. That observation (M102443995L) swept up the first U.S. lander very early in LRO's Commissioning phase, in orbit 272, when LRO was still flying at twice its Nominal mission altitude, from 102.4 km overhead. That survey of the floor of Flamsteed P was photographed at less than half of the planned LROC NAC resolution; at 1.08 meters per pixel, the Surveyor 1 tripod in profile was barely visible, identifiable mainly in its long shadow at local sunset.The Surveyor design featured a central mast with square solar panels at the top, standing high like a flag. That aided in identifying all five of the successful Surveyor landers, right they sat. 


Unlike its Google Earth icon, seen in Fig. 1, Luna 9 was not standing like an egg, balanced on one hemisphere. After its landing and activation Luna 9 was at tilted, and from slight changes in the background seen in its five photographic panoramas we can tell Luna 9 shifted slightly after deployment.

Fig. 4  Simulated oblique view west by northwest over the area of interest from a point 28 km over the western Oceanus Procellarum. After years of deconstructing the five panoramas captured and returned to Earth by Luna 9, many reliable experts have come to doubt the accuracy of the official landing site (coordinates on the left, at "-1310 m" elevation).  Some believe Luna 9 must have landed somewhere in the plain to the north (on the right, marked "-1640 m").  If the object detailed in Figures 5 and 6 below is Luna 9 then the lander came to rest at a point less than three kilometers and almost due north of the official coordinates ("-1170 m"), and at least 140 meters higher in elevation.  After studying the LROC WAC Digital Terrain Model of the area (Fig. 2) the hills, contiguous with other features surrounding the Plain of Descent, appear to be the highly degraded rim of an ancient, mostly buried crater.  -Image created using ILIADS application, developed by NASA's LMMP project; photography from LROC WAC Global Mosaic with elevations from LOLA altimetry (v.2). [NASA/GSFC/ARC/LMMP/ASU].
The low profile and squat, efficient design of Luna 9 have made it difficult to definitively locate, either somewhere in the expansive plain to the north or near the official position somewhere on a 500 meter high hill, nor on their slopes. All of the area was extensively photographed from LRO, from high altitudes and low, under high Sun and low Sun, with LRO rolled and looking down from directly overhead. If the little vehicle has been captured (which seems certain) what would distinguish its egg shape from thousands of boulders more or less the same size?

It's a safe bet Samuel Lawrence and others on the LROC team encountered this difficulty head-on, with the determination and resourcefulness of a Cold War photo-analyst pouring over U2 photographs of Cuban missile sites. 

In fact, it would be the height of presumption on our part to claim to have done anything more than retraced their steps. It's impossible to believe a candidate object we stumbled on, within their choices of photographic session, hasn't already been considered or scratched off the list. Were it not for something that may turn out to be simply an artifact of digital compression we wouldn't take another look.

Let's just say, "boy, that sure looks like Luna 9!"

What follows are two sets of images, selected from two separate LROC NAC observations, focused on an "object of interest" at sunrise (Figures 5a and 5b), when the Sun was less than 5 degrees over the east horizon, when long shadows allow for depth perception, and then (in Figures 6a - 6d) where, at less than 8° north of the equator, the Sun was high overhead and depth perception gives way to a search for subtle variations in brightness or optical maturity.


Fig. 5a   The full 2.5 kilometer-wide field from LROC NAC M132071202L orbit 4597, June 25, 2010; with resolution greatly reduced from the original 0.48 meter per pixel resolution captured from 40.49 km altitude, incidence angle 85.57°. The yellow rectangle is the area shown at full resolution in Fig. 5b, immediately below. The yellow dot is our "object of interest," so to speak, indicated with an arrow in at full resolution below. The object certainly casts a shadow, as anything with a profile would when caught in naked morning sunshine on the Moon. It is also seemingly brighter than other similarly sized objects in the roughly 238 meter-wide field of view seen below.  [NASA/GSFC/Arizona State University].
Fig. 5b  Full resolution, and very non-definitive rendition of the Object of Interest, again, from LROC NAC M132071202L The object appears to be situated within the west slope of a 10 meter crater, whose interior is very darkened with shadow. Since Luna 9 arrived on the Moon not long after local sunrise, this doesn't help identify the object as Luna 9. The larger, similarly bright object to the southwest is too large to be Luna 9, but its size and location relative to the object of interest makes a case for it being part of the larger lander bus [NASA/GSFC/Arizona State University].
On the 500 meter hills, south of "the plain of descent," under an afternoon Sun:

Fig. 6a  Backing away once again, shifting perspective slightly to the west, with the Sun nearly overhead, this is the field of view within the rectangle back in Fig 3, and slightly west, overlapping the area in Fig. 5a, another 2.5 km-wide area taken this time from LROC NAC M137970706R, orbit 5466, September 1, 2010, from 45.57 km in altitude (incidence angle 29.64°). The area in the white rectangle is the field of view enlarged in Fig. 6b, immediately below [NASA/GSFC/Arizona Sate University].
Fig. 6b  At 40 percent of their original resolution, line 14775 to 15556 by sample 3964 - 4544 from M137970706R. (The dim dark line is an artifact "junction" between line 15000 and 15001). And, like a Russian Doll, the square box above is the roughly 290 meter-wide field of view seen at 100 percent of the original observation's 0.5 meter per pixel resolution seen in Fig. 6c, immediately below [NASA/GSFC/Arizona State University].
Fig. 6c At full resolution, lines 15001 - 15580 by sample 3964 - 4543 from LROC NAC M137970706R. Compare this with Fig. 5b, above and, once again, what is seen under differing lighting conditions on the Moon is clear. When happening upon this candidate object under a high Sun, something catches the eye [NASA/GSFC/Arizona State University].
Fig. 6d  Taking  LROC NAC M137970706R  well beyond its true limit of resolution we stumble upon what might be Luna 9, resting on the west interior slope of a shallow 10 meter crater, perhaps even afterwards sliding slightly between photographic panoramas, February 3, 1966. Under an early afternoon Sun, after being enlarged 400 percent with a super-sampling algorithm, what appear faintly as three of the spacecraft's four instrument-shielding petals (the fourth presumably in its shadow) somehow popped out from the background. No intentional fudging was done to the original brute-force enlargement (See Fig. 7) [NASA/GSFC/Arizona State University].
Fig. 7 A simple enlargement to 400 percent of the half-meter per pixel resolution native to LROC NAC observation M137970706R turned up this object, certainly an oddity if it is not Luna 9. As demonstrated in the hackneyed animated image (Fig. 6d), the object meets the profile, is barely less than 3 kilometers due north of its official landing site, about 140 meters higher in elevation, on a broader slope with presumably less obstructed horizon.

Fig. 8 The view south from Luna 9, February 3, 1966.



Using the popular open-source program Orbital Simulator, "reseferina1" created this interesting simulation of the Luna 9 mission in 1966. Though fun, it too, unfortunately, made the thing look far too easy. The originating YouTube page is HERE.

Friday, December 2, 2011

LROC: Lichtenberg B flow

Starting at the rim of the crater Lichtenberg B, impact melt flowed and formed a channel, pushing boulders aside in the process. LROC Narrow Angle Camera (NAC) M120257109R, LRO orbit 2856, February 8, 2010; field of view 430 meters, incidence angle is 57° from 40.39 km. See the full sized LROC Featured Image HERE [NASA/GSFC/Arizona State University].
Sarah Braden
LROC News System

Lichtenberg B crater, located at 33.3°N, 61.5°W in northern Oceanus Procellarum, is a young lunar crater with a sharp rim, ejecta rays, and impact melt. 

Along the south rim, impact melt formed channels before cooling enough to come to a rest and solidify. In the Featured Image it appears that the flow of impact melt pushed boulders towards the edges of the flow, leaving behind an outline of its path. Other ejecta from the crater may have also played a role in forming the channel, since it is unclear if the amount of impact melt seen in the image is enough to have carved out the channel.

For context, Lichtenberg B from LROC Wide Angle Camera (WAC) observation M120256944C, imaged during the same pass, and the arrow marks the location of the area detailed in the LROC NAC Featured Image. The flows are located on the southern edge of the rim. Also from LRO orbit 2856, February 8, 2010; resolution 57.48 meters per pixel. View the original LROC WAC context image accompanying the release HERE [NASA/GSFC/Arizona State University].
An expanded view of the LROC Featured Image. The blue arrow points to the first part of the flow, where the channel is roughly 30 meters wide. The white arrow points to the ridge of boulders that form the sides of the channel and the red arrow points to where the flow ends, where the impact melt was topographically high to flow through a channel. View the full sized expanded image HERE [NASA/GSFC/Arizona State University].

Explore the full NAC frame of Lichtenberg B!

Related Posts:
Impact melt tongue
Channelized impact melt
Rootless impact melt flows
Splash and flow

Thursday, December 1, 2011

DLR: Flying over the three-dimensional Moon

Unnamed massif on the north-northeast rim of South Pole-Aitken basin at 22.62°S, 203.92°E, (8,550 meters above mean global elevation) is a lofty overlook of the Wisling and Plummer crater groups southwest of Korolev (top right). The remarkably short distance between the Moon's lowest spot, within Antoniadi, and it's highest point, on the rim of Engel'hardt crater, seen here on the horizon, can be traversed in the LROC WAC Digital Terrain Model (DTM) in videos downloadable at the DLR English-language website HERE [NASA/GSFC/ASU/DLR].
Although the Moon is so far the only celestial body other than Earth on which a human being has ever walked, the topography of its surface has not been studied comprehensively. This is why NASA's Lunar Reconnaissance Orbiter (LRO) has been orbiting the Moon since June 2009, using a wide-angle camera to digitally record its cratered surface. Using a total of 70,000 images, researchers at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) have now created a digital 3D model of the Moon with unprecedented accuracy and completeness. The video shows a number of virtual flights over the surface of Earth’s satellite.

The landing sites of Apollo 11, 12 and 14 are located centrally in a region depicted in tranquil blue. In these color-coded 3D images of the lunar surface, blue is used to indicate low-lying flat ground. It was not until the later missions that the US became more adventurous in the choice of a landing site. For example, the astronauts on the Apollo 15 and 17 missions were sent into regions of the Moon that posed a much greater challenge.  In the model created by the DLR Institute of Planetary Research in Berlin-Adlershof, these areas are depicted in green – indicating that these regions are at a slightly higher elevation, and are not as flat as those used for the earlier Moon landings. To make this 3D depiction possible, the wide-angle camera (LROC WAC) on board the American LRO spacecraft recorded images from an altitude of 50 kilometers. In the next step, DLR project scientist Frank Scholten from the Institute of Planetary Research evaluated the 70,000 stereo images, using special software to compare them pixel by pixel, then used the information relating to where the picture was taken and the direction of view of the camera to calculate roughly 100 billion 3D points. The result is a 3D model covering about 37 million square kilometers, which is more than 98 percent of the lunar surface and over twice the area of Russia.
Full range of the full-resolution DLR video tour of the LROC DTM. A very small section was cropped to create the view further up  [NASA/GSFC/ASU/DLR].
The Moon in focus It took a network of 40 computers two weeks of computing time to perform these elaborate calculations. The software required for this task was developed at the DLR Institute of Planetary Research and had already been employed successfully on image data from other planets; for example, the Mars Express mission. The result, known as the GLD 100 (Global Lunar Digital Terrain Model), delivers elevation figures at 100-metre intervals right across the surface of the Moon. "Over the last few years, planetary research has been focusing primarily on other planets, Mars being just one example. The Moon remained in the background during this period," explains Scholten. The team led by DLR planetary researcher Jürgen Oberst performed its measurements of the Moon in several different ways. Camera imagery was complemented by data from the Lunar Orbiter Laser Altimeter (LOLA), which employs laser pulses to measure elevations on the lunar surface; these were then compared with the data in the GLD100 elevation model. These two methods complemented one another; the laser instrument provides extremely accurate elevations, but covers only part of the lunar surface. Gaps of several kilometers still exist, particularly in regions near the lunar equator. The cameras on board the LRO compensate for this because they are able to completely cover large areas. "Our elevation model will help planetary researchers to examine questions for which an accurate and complete knowledge of the topography of the Moon is important," says Scholten. With this data, scientists wish to investigate a number of things, including whether the central latitudes of the Moon are home to any deep craters where water ice might exist in the permanent shadows - in a similar way to the regions close to the two poles.

The elevation model clearly depicts the diverse landforms – for example, mountains, craters and rilles. The color-coded view depicts the third dimension – altitude – in colors ranging from blue (roughly -9100 meters) to red/white (roughly +10,760 meters). Whereas the 'front', or Earth-facing side of the Moon, with its flat plains, or mares, and the Apollo landing sites, appear for the most part in blue and green, the hitherto relatively unexplored far side of the Moon – the side not visible from Earth – has its high ground depicted in red. This far side is home to the lowest as well as the highest points on the Moon. "This depiction clearly shows how gigantic and deep the South Pole Aitken Basin is," explains DLR planetary researcher Ulrich Köhler. This basin has a diameter measuring about 2500 kilometers, making it the largest known impact crater in the Solar System. It is about 13 kilometers deep "and is perhaps a window on the distant past of the Moon because it may extend down to the original mantle," suggests Köhler. Using the data from this elevation model, scientists can also simulate low-altitude flights across the lunar surface. The 'sightseeing' flights over the Apollo 15 and Apollo 17 landing sites show clearly that the astronauts landed close to mountain ranges some several thousand meters in height and set out from there to explore the Moon.

Hadley Rille Valley and the landing site of the 1971 Apollo 15 expedition, a second still from the high resolution DLR tour of the LROC WAC Digital Terrain Model [NASA/GSFC/ASU/DLR].
"With this data, we are laying important foundations for future Moon missions, whether manned or unmanned," states lunar researcher Ulrich Köhler. "These 3D maps of the Moon enable us to better evaluate future landing sites.” There are a total of seven instruments on board the NASA orbiter; DLR Space Administration funds the German members of the LRO team. With each new orbit of the Moon, and with each new image of the lunar surface, the planetary researchers are able to further refine their 3D model of Earth's companion.

"Every month, we cover the entire surface of the Moon once more with the camera,” explains Frank Scholten. “This data is included in our model on a continuous basis, which enables us to view the surface in ever greater detail."

Download and/or view the DLR tour in one of three available resolutions, HERE.

Reference: LROC's New Global Lunar Topography

The latest destination for human spaceflight?

Next stop?
Paul D. Spudis
The Once and Future Moon
Smithsonian Air & Space

Of all the idiocies that make up our current lack of a genuine policy for civil space, the imperative to find some destination that is not the Moon is the most telling sign of an absence of thoughtful leadership.  For an example of the pointlessness to which this reasoning can go, take a look at a recent post at Scientific American, arguing for a human flyby mission to Venus.

Don P Mitchell's excellent perspective corrections performed on necessarily distorted photographs from the surface of Venus obtained by the Soviet Venera landers, in this case Venera 13. Crushing atmospheric pressures, very dynamic corrosion and kiln-like temperatures doomed Venera 13 after slightly over 2 hours.
That’s right – Venus.  The planet that makes Jupiter’s moon Io look like an island in the Bahamas.  That locale of sea-bottom pressures, lead-melting temperatures and sulfuric acid rain.  Specially built robotic devices last for (at best) an hour or two before breaking down into an inert lump of metal.  This place is now being advocated (seriously) as a destination for human spaceflight.  How did we arrive at such a state?

Lost Horizon - the Altair manned lander turned out to be the only
Constellation program truly eliminated by Congress. Other
components remained or eventually resurfaced under different names.
Simple – by a deliberate act of programmatic destruction.  The Moon was to be our first destination on the long road into the Solar System.  But that goal was discarded, allegedly on the grounds that “we’ve been there,” but in reality because it was a destination that could be reached on reasonable timescales for affordable amounts of spending.  Thus, a failure to return to the Moon could not be blamed on factors other than program mismanagement or agency incompetence.  In other words, it was a realistic goal against which progress could be assessed.

What replaced lunar return?  That’s a bit more muddled, but vague notions were advanced that human missions “beyond low Earth orbit” could be undertaken only if NASA was freed from the onerous requirement to build new spacecraft and launch vehicles.  Thus, we would purchase commercial launch services for delivery of people and payload to LEO and use the agency budget to develop “new and exciting technologies” to make more distant goals reachable.

As this proposed pseudo-policy played itself out over the ensuing months, its essential hollowness became ever more apparent.  Despite the quasi-religious beliefs of some space buffs, there is no “magic beans” technology to make spaceflight infinitely cheap and infinitely capable.  There is no commercial human spaceflight industry.  And other than the now-discarded lunar surface, there is no worthwhile human destination reachable within the next 15 years.

Yet many in the space business pretend otherwise.  Hence, we get articles like the “Humans to Venus” piece.  What’s wrong with this concept?  Simply put, there is nothing humans can do on a Venus flyby that a robotic spacecraft could not accomplish, while there are things a robotic spacecraft could do there that humans cannot.  

The real need for Venus is to get high-resolution radar images and gravity data of the planet to extend and supplement the reconnaissance mapping of the Venera and Magellan missions of the past century.

To get such high-quality image data, one must put a spacecraft into orbit around Venus.  This is a fairly straightforward task for a robotic mission; you can use the atmosphere of Venus to aerobrake, which will gradually slow the spacecraft down and allow it to slip into orbit.  The problem is not getting into orbit around Venus – it’s getting out of it.  Venus is a large planet (almost as big as the Earth) and it takes significant energy to achieve escape velocity.  With a robotic spacecraft, we don’t worry about that because there is no need to return it to Earth.  I suspect that a human crew might feel differently about such a proposition.

In plain fact, there is nothing of any real scientific value that a human crew can do during a few-minutes-long flyby encounter with Venus.  So we are talking about undertaking a months-long trip through interplanetary space, fully exposed to cosmic radiation and solar particle events, for a momentary view of an extremely hot planet of bright, featureless cloud tops.

Space advocates are desperately looking for something people can do and somewhere they can go in space on timescales of less than multiple decades at costs of less than hundreds of billions of dollars.  If only there where some place we could get to within a decade or so, for a cost that doesn’t bust the latest budget.  If only there was a destination in space where human judgment, knowledge and expertise would play a real time critical role in mission success and where new capability would be realized.

If only…..


Originally published December 1, 2011 at his Smithsonian Air & Space blog The Once and Future Moon, Dr. Spudis is a senior staff scientist at the Lunar and Planetary Institute. The opinions expressed are those of the author and are better informed than average.

Wednesday, November 30, 2011

LROC: Layered basalt on the wall of Marius A

Layered basalt on the wall of Marius A crater partially covered by debris flow. The crater rim is to the right and the crater floor is to the left. LROC Narrow Angle Camera (NAC) observation M137848463R, LRO orbit 5448, August 30, 2010; field of view of the original LROC Featured Image (HERE) 460 meters, at an illumination incidence angle of 33° from an altitude of 44.37 kilometers [NASA/GSFC/Arizona State University].
Sarah Braden
LROC News System

Marius A (12.58°N, 46.05°W) is an approximately 15 kilometer crater located in Mare Insularum. The Featured Image shows basalt layering partially covered by streaks of granular material that slid down from higher up on the wall. Craters with visible basalt layers like Marius A are windows to the history of basalt deposition. 

Each thin layer seen in the wall of Marius A is probably a single flow or flow lobe, each spreading out across the lunar surface due to the low viscosity of mare basalt (basalt has a viscosity similar to that of ketchup). How much time passed between each layer is still an unanswered question. By studying many craters with visible basalt flows, however, scientists may be able to piece together a more detailed, local history for the various mare on the lunar surface. Not all craters in the mare have visible mare basalt layering, though. Additionally, over time post-impact processes like the debris in today's Featured Image and slumping of the crater walls reduce the visibility of basalt layers.

Marius A at 62 meters resolution from LROC Wide Angle Camera (WAC) observation M135493956C, orbit 5101, August 3, 2010 in a field of view roughly 42 km across; incidence angle 57.09° from 44.1 km above. The much small field of view shown in detail in the Featured Image released November 29, 2011 is located at just shy of "3 o'clock" on the east crater rim wall [NASA/GSFC/Arizona State University].
LROC WAC context image of Marius A crater. The image is 59 km across and the rectangle indicates the area of the whole NAC frame from which the Featured Image is taken. View the full size and original LROC WAC context image HERE [NASA/GSFC/Arizona State University].

There are many craters with visible basalt layers and LROC has given us our first look at these incredible details of the lunar surface. Check out the NAC frame of Marius A and then explore the rest of the lunar maria!

Related Posts:
Layering in Euler Crater
Lava Flows Exposed in Bessel Crater
New Views of Lunar Pits

Marius A in a wider oblique context view from a virtual point 254 kilometers over the bright landmark crater Kepler, showing some of the more famous landmarks also nearby. One of the wispy rays of material and reflective secondary craters, superimposed upon Marius A by the Kepler impact event crosses directly upon Marius A and beyond, a distance of 280 kilometers from crater center to crater center [NASA/LMMP/GSFC/ARC/ASU].

Tuesday, November 29, 2011

LROC: Dionysius Detour

A high albedo granular flow traveled down the wall of Dionysius crater. Why is the flow curving around the crater floor? LROC Narrow Angle Camera (NAC) M111484008R, orbit 1563, October 29, 2010; incidence angle 26.934° with a resolution of 0.51 meter per pixel from 48.11 kilometers. Image filed of view is 500 meters. View the full size LROC Featured Image HERE [NASA/GSFC/Arizona State University].
Drew Enns
LROC News System

Craters on the Moon often develop granular flows on their walls as loose material slides towards the bottom.

As this process occurs the granular flows must overcome any obstacles in their path to reach the crater floor.  Dionysius, an 18 kilometer crater on the western edge of Mare Tranquillitatis, is no exception.



The curved termination of the talus is the result of series of granular flows with an impact melt mound blocking the immediate path of the flow.

LROC Wide Angle Camera image (604 nm) of Dionysius with the subject impact melt marked with the small yellow arrow. LROC WAC observation M148871990C, orbit 6778, December 13, 2010; resolution 59.4 meters per pixel from 43.19 kilometers altitude [NASA/GSFC/Arizona State University].
Because the granular flow cannot go over the mound, it is being redirected along the mound's slope until it reaches the crater floor. The result is a spectacular arc that acts as a geologic contact between the granular flow on one side and impact melt on the other!

Are any other geologic features redirecting the granular flow in the full NAC frame?

Related Posts:
Lunar landslides!
Dichotomy
Impact melt in Anaxagoras crater