Friday, January 27, 2012
Remnant magnetism hints at once-active lunar core
 |
| A piece of lunar sample 10020, a rock that appears to carry the signature of a past magnetic field on the moon [NASA]. |
The moon of today is a static orb with little to no internal activity; for all intents and purposes it appears to be a dead, dusty pebble of a world. But billions of years ago the moon may have been a place of far more dynamism—literally.
A new study of a lunar rock scooped up by Neil Armstrong and Buzz Aldrin during their Apollo 11 mission indicates that the ancient moon long sustained a dynamo—a convecting fluid core, much like Earth's, that produces a global magnetic field. The age of the rock implies that the lunar dynamo was still going some 3.7 billion years ago, about 800 million years after the moon's formation.
That is longer than would be expected if the lunar dynamo were powered primarily by the natural churning of a cooling molten interior, as is the case on Earth. The moon's small core should have cooled off rather quickly and put an end to any dynamo-generated magnetic field within a few hundred million years. So researchers may have to explore alternate explanations for how a dynamo could be sustained—explanations that depart from thinking of the lunar interior in terms of Earthly geophysics.
A standard-issue, Earth-like dynamo "would have died out on the moon much, much before 3.7 billion years ago," says Erin Shea, a graduate student in geology at the Massachusetts Institute of Technology and lead author on a study in the January 27 issue of Science. "We have to start thinking outside the box about what generates a lunar dynamo."
A new study of a lunar rock scooped up by Neil Armstrong and Buzz Aldrin during their Apollo 11 mission indicates that the ancient moon long sustained a dynamo—a convecting fluid core, much like Earth's, that produces a global magnetic field. The age of the rock implies that the lunar dynamo was still going some 3.7 billion years ago, about 800 million years after the moon's formation.
That is longer than would be expected if the lunar dynamo were powered primarily by the natural churning of a cooling molten interior, as is the case on Earth. The moon's small core should have cooled off rather quickly and put an end to any dynamo-generated magnetic field within a few hundred million years. So researchers may have to explore alternate explanations for how a dynamo could be sustained—explanations that depart from thinking of the lunar interior in terms of Earthly geophysics.
A standard-issue, Earth-like dynamo "would have died out on the moon much, much before 3.7 billion years ago," says Erin Shea, a graduate student in geology at the Massachusetts Institute of Technology and lead author on a study in the January 27 issue of Science. "We have to start thinking outside the box about what generates a lunar dynamo."
A lunar sample collected by Apollo astronauts suggests that other-Earthly geophysics drove the moon's churning interior
Using a high-resolution magnetometer, the researchers found that the lunar sample indeed formed in the presence of a magnetic field, perhaps even one as strong as Earth's magnetic field today. "What this sample tells us is that at some point the moon did have a dynamo," Shea says. "This magnetic field lasted much longer than we had considered before."
A similar paleomagnetic study in 2009 by some of Shea's co-authors demonstrated the presence of a lunar dynamo some 4.2 billion years ago. That is just at the cusp of what would be possible with an Earth-like dynamo driven by a cooling interior alone. "Even then it's not trivial," says Ian Garrick-Bethell, a planetary scientist at the University of California, Santa Cruz (U.C.S.C.), who was the lead author of the 2009 study.
A similar paleomagnetic study in 2009 by some of Shea's co-authors demonstrated the presence of a lunar dynamo some 4.2 billion years ago. That is just at the cusp of what would be possible with an Earth-like dynamo driven by a cooling interior alone. "Even then it's not trivial," says Ian Garrick-Bethell, a planetary scientist at the University of California, Santa Cruz (U.C.S.C.), who was the lead author of the 2009 study.
Read the full online article HERE.
LROC: Pytheas
 |
| A lovely combination of layered mare basalt, granular flow, and talus. The top of the image is down-slope. LROC Narrow Angle Camera (NAC) observation M170694505L, orbit 10289, September 15, 2011; image field of view is 735 meters, pixel scale of 0.49 meters per pixel from 45.53 kilometers. See the much larger full sized LROC Featured Image HERE [NASA/GSFC/Arizona State University]. |
LROC News System
Inside the southern rim of the crater Pytheas (20.55°N, 20.6°W) is a great combination of layered mare basalt, granular flow, and talus. In the bottom left hand corner of the Featured Image you can see the details of erosion where granular material fell away from the rest of the surface near the rim. The high reflectance (bright) tendril of material flowed in a narrow band over the layers of lower reflectance (darker) mare basalt, then, after clearing the basalt layers, finally spread into a wide cone of talus. Talus cones are common on the Earth, with some stunning examples that may rival the Moon's beauty. On the Moon, talus deposits are created entirely by gravity, but on the Earth wind and water play a role in their formation.
 |
| A somewhat 'twisted' view of the larger slope context of the granular flows in the Featured Image from the LROC NAC frame. The apparent floor contact is, in fact, far from the crater's lowest elevations, on the opposite side of Pytheas [NASA/GSFC/Arizona State University]. |
 |
| A particularly detailed LROC Wide Angle Camera (WAC) monochrome (604 nm) 66 meter per pixel resolution image of Pytheas and Pytheas D directly to its north, the topography of its interior, and exterior ejecta blanket as well as albedo chevron, stitched from three sequential orbital viewing observations under an average 54.7° incidence angle from 46.8 kilometers, November 18 and 19, 2010 [NASA/GSFC/Arizona State University]. |
 |
| The same LROC WAC 604 nm mosaic at 50 percent (132 meter) of its original resolution offers a fuller view of the Pytheas chevron and other rays, apparently "downwind" from the Copernicus impact. The small crater to the west of Pytheas is Pytheas A. The inset shows elevation range of the Pytheas environs from LROC's versatile QuickMap [NASA/GSFC/Arizona State University]. |
 |
| Pytheas and the south-central Imbrium basin clearly had their topography and appearance affected by the relatively recent arrival of the Copernicus progenitor, 800 million years ago. LROC WAC 100m Global Mosaic overlaid upon LOLA digital elevation model (v.2) in the NASA ILIADS application [NASA/GSFC/Arizona State University]. |
Explore the entire NAC frame, HERE.
Related Posts:
Dawes
Marius A
Lava Flows Exposed in Bessel Crater
Thursday, January 26, 2012
LROC: Dawes
 |
| Layers of mare basalt affected
the paths of granular material that flowed down the crater wall. The top of the image is down-slope |
LROC News System
The wall of Dawes crater (17.21°N, 26.32°E) contains sections of spectacular mare basalt layering. However, mass wasting, a geologic process where material moves downhill due to gravity, has started to partially cover these beautiful outcrops.
Granular flows started above the outcrop and then flowed down the interior crater wall. As seen in the Featured Image, the topography of basalt outcrop caused the flow to deviate into narrow paths, away from a simple path flowing straight down the crater wall. As the crater Dawes ages over billions of years, the mare basalt outcrop will eventually be completely covered with granular material due to slumping of the crater's walls and more mass wasting.
 |
| The full width of LROC NAC M157418698 |
 |
| Through the last release of LROC Narrow Angle imagery, all but the center swath of Dawes has been photograph |
 |
| Dawes has an asymmetric |
 |
| WAC/topographic context image of 17.8 km diameter Dawes [NASA/GSFC/Arizona State University]. |
Related Posts:
Marius A
Detour!
Dry debris or liquid flow?
Boulder Mound
Gingrich: 'Let’s make the Moon a State.'
 |
| Admiral Alan B. Shepard, Jr., USN (1923-1998), the first American in Space and fifth human to explore the lunar surface as commander of Apollo 14 poses with the third of six U.S. flags deployed on the Moon, February 5, 1971 [NASA/JSC]. |
"When they have 13,000 Americans living on the moon, they can
petition to become a state," Gingrich said to applause at a speech on
Florida's Space Coast. "By the end of my second term, we
will have the first permanent base on the moon, and it will be American."
During the GOP presidential debate carried on CNN, Thursday, Jan. 26 at the University of North Florida in Jacksonville former Massachusetts Governor Mitt Romney ridiculed the idea as mere pandering to Floridians on the Space Coast suffering in a tough economy.
"If I were the CEO of a Fortune 500 company," Romney said, "and an aide came to me with the suggestion that we invest in a colony on the Moon I would fire him."
Former Senator Rick Santorum (R-PA) remained open minded, he claimed, while U.S. Rep. Ron Paul (R-TX) said government should be taken out of the way. Meanwhile former Speaker of the U.S. House Newt Gingrich (R-GA) reiterated an idea some have called 'grandiose' as necessary to inspire young Americans to study the sciences. He looked forward to a day, he said, when the Kennedy Space Center hosted six launches a day.
Somewhat lost in the crossfire of a heated presidential primary contest among U.S. Republicans fighting one another for the opportunity to unseat Barack Obama in November is a simple truth the candidates and their camps failed to grasp. Until 2009 establishing a permanent human presence on the Moon was official National Space Policy in the United States.
During the GOP presidential debate carried on CNN, Thursday, Jan. 26 at the University of North Florida in Jacksonville former Massachusetts Governor Mitt Romney ridiculed the idea as mere pandering to Floridians on the Space Coast suffering in a tough economy.
"If I were the CEO of a Fortune 500 company," Romney said, "and an aide came to me with the suggestion that we invest in a colony on the Moon I would fire him."
Former Senator Rick Santorum (R-PA) remained open minded, he claimed, while U.S. Rep. Ron Paul (R-TX) said government should be taken out of the way. Meanwhile former Speaker of the U.S. House Newt Gingrich (R-GA) reiterated an idea some have called 'grandiose' as necessary to inspire young Americans to study the sciences. He looked forward to a day, he said, when the Kennedy Space Center hosted six launches a day.
Somewhat lost in the crossfire of a heated presidential primary contest among U.S. Republicans fighting one another for the opportunity to unseat Barack Obama in November is a simple truth the candidates and their camps failed to grasp. Until 2009 establishing a permanent human presence on the Moon was official National Space Policy in the United States.
Wednesday, January 25, 2012
'Everybody has won, and all must have prizes'
Paul D. Spudis
The Once and Future Moon
Smithsonian Air & Space
 |
| The Dodo rewards Alice's own thimble back as a prize, from Alice's Adventures in Wonderland. |
This model structure harkens to early days of aviation when prizes for specific aeronautical achievement proliferated. Notable was the $25,000 Orteig Prize offered by New York hotelier Raymond Orteig for the first non-stop air flight between New York and Paris. Charles Lindbergh won the Orteig Prize in 1927 in his specially built Spirit of St. Louis. After this flight, probably due more to celebrity culture and the frenzy of fame rather than actual flight accomplishment, commercial aviation enjoyed a boom of popularity with the public and industry. In short, the prize offering succeeded in producing a PR stunt; the design features of Spirit of St. Louis were specifically optimized to permit Lindbergh to win the prize, not to advance aeronautical technology or establish commercial transatlantic flight operations.
Currently, the most visible prize structure for spaceflight is Peter Diamandis’ X-Prize Foundation, a private funding group that awards prizes for specific space-related goals. The first and most famous, the Ansari X-Prize founded in 1996, was offered to the first non-government group that could (within two weeks) twice launch and safely return to Earth a reusable, manned spacecraft. In 2004, the $10,000,000 X-Prize was won by Burt Rutan’s SpaceShipOne, funded by Microsoft’s Paul Allen. This vehicle used an innovative airborne launch system, a hybrid solid-liquid rocket engine and a “wing feathering” method for re-entry and return flight. Plans were immediately made to construct a commercial version of SpaceShipOne, to be sponsored and operated by Richard Branson’s Virgin Galactic organization.
However, since that prize-winning flight almost eight years ago, things have not proceeded smoothly. An explosion in 2007 destroyed the rocket fabrication facility and killed three workers. Virgin Galactic established an operations base in New Mexico on October 17, 2011. There is a passenger manifest backlog of 455 subscribers but as of this writing, not a single commercial passenger spaceflight has occurred.
Another current space prize is the Google Lunar X-Prize, offering a $20 million award for successfully landing a spacecraft carrying a high-definition imaging system and roving on the Moon at least 500 meters. Since its announcement in 2007, over 30 companies have registered to participate in the competition. Additional prize increments are awarded for other accomplishment, such as long range (> 5 km) roving, survival over a lunar night, and documentation of the presence of water in lunar soil. No lunar mission has yet been launched nor has any launch date been announced. The original expiration date for the lunar X-Prize was 2012 but was extended to the end of 2015.
An alternative incentive approach is milestone-based contracting. NASA’s Commercial Orbital Transportation Services (COTS) program awards government money to companies that meet specific milestones on previously announced timescales. That money is to be spent developing specific capabilities required for government needs. The reward at the end of this cycle is a performance-based government contract for launch services. However, under this government-sponsored incentive program, a commercial human spaceflight industry has yet to develop.
Bigelow Aerospace, a builder of private, “For Lease” space stations, recently laid off over one third of their workforce. Part of the problem is the lack of assured, commercially available access to their orbital stations. In 2004, Bigelow himself established and funded a $50 million prize to develop a commercial crew vehicle for orbital transport; the prize expired in 2010 without a single attempt at flight. Although rumor has it that Boeing is developing a spacecraft to serve private space stations, nothing has yet appeared, even in prototype form. Due to some unidentified technical issues, SpaceX has delayed the launch of the first flight of their Dragon cargo vehicle to ISS from early next month to an unspecified future date.
The simple glaring fact is the United States has no commercial human spaceflight industry. NASA’s attempt to encourage the development of such through COTS is floundering against some unpleasant realities: it is both very difficult and very costly to get into and back from space. The former drives up the cost, severely limiting potential markets. The latter stops not only imagined demand (such as space tourism) dead in its tracks but also real demand, such as government contracts for ISS crew access.
The hope of space prize enthusiasts for explosive growth in space similar to that seen in aviation innovation and industry following the winning of the Orteig Prize is unlikely to be realized. The problem is that spaceflight is a vastly more difficult field in which to participate than aviation. Many amateurs could and did fabricate aircraft in their garages and barns in the early decades of the last century. The First World War made surplus aircraft widely available at low cost, furthering the development of a robust early aviation industry. In contrast, no one has flown a surplus government space vehicle and “barnstorming” rockets do not exist, despite some imaginative depictions in Hollywood films.
Unfortunately, this is the space program we now have. No American human spaceflight flight systems exist and their development is dependent on the advent of a demand that has not yet materialized. Meanwhile, we comfort ourselves with fantasies about human missions to Mars. I appreciate and applaud Gingrich’s enthusiasm for space, a visionary attitude sorely lacking in most politicians. He needs to think carefully about how to incentivize the development of space and about the critical national needs served by our civil space program. Prizes seem attractive because of their historical role in stimulating a nascent aviation industry. But significant differences between aviation and spaceflight and our primitive level of development of the latter suggest that what worked before may not work now.
Originally published January 25, 2012 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.
LROC: Brayley G
 |
| This small (around 140 meters across) crater is perched on the edge of something much more extraordinary. LROC Narrow Angle Camera (NAC) frame M175515801L, November 9, 2011 30 cm pixel scale, field of view 300 meters across. View the full size LROC Featured Image HERE [NASA/GSFC/Arizona State University]. |
LROC News System
The impact crater in today's Featured Image rests on the edge of another crater known as Brayley G, however this crater is most likely volcanic! Brayley G is a beautiful volcanic vent located in the mare at 24.2°N, -36.4°E. In 2008, before LROC launched, we wrote about Brayley G in the Apollo Image Archive Featured Image.
Today we are proud to present a LROC NAC mosaic of the 3 km wide and less than 5 km long feature. Compare the new LROC NAC observation to images from Apollo 15 and 17 in the graphic below (or visit the Apollo Image Archive). Note how the differences in incidence angle highlight different features within Brayley G. The higher-incidence Apollo images highlight the morphology of the edges of the vent and the concentric faults. The lower-incidence LROC NAC image reveals the interior of Brayley G, which contains many boulders along the inside wall and more collapse features.
 |
| The same small crater (white arrow) in the context of the ancient Brayley G vent, from the full field of view seen in the LROC NAC mosaic released January 24, 2011. Below, a side by side comparison (original HERE) of Apollo 15 and Apollo 17 orbital mapping camera images. Because of LRO, it's now possible to see the interior of this volcanic feature [NASA/JSC/GSFC/Arizona State University]. |
So how do scientists tell the difference between a volcanic vent and an impact crater? Most lunar craters are bowl-shaped and circular depressions with raised rims. When an impact occurs it excavates material from below the surface and ballistically ejects that material outward from the point of impact. This process leaves a visible ejecta blanket around the crater rim. Over time, erosion and slumping of crater walls can degrade and eventually remove an elevated crater rim. Studying examples of small, recent impacts shows the link between these physical processes and the surface features they leave behind. Volcanic vents, on the other hand, are usually not circular and they do not have raised rims. While volcanic vents do not have impact ejecta blankets, they can be surrounded by a "halo" of pyroclastic material from a past eruption.
 |
| Above: Closer isn't necessarily 'better,' ascetically speaking. From barely 27 kilometers above, and under a bright local mid-afternoon Sun (incidence 45.41°), LROC Wide Angle Camera (WAC) observation M168441281C (604 nm) from orbit 9958, August 20, 2011; raw resolution 43.4 meters per pixel. Below, from 45.8 kilometers (and superior alignment of the image 'framelets') and under a lower local morning Sun (incidence 55.64°), LROC WAC observation M144863532C (643 nm); context image of the Oceanus Procellarum mare surrounding the 3 kilometer across Brayley G vent. The white arrow again marks the location of the small crater on the edge of Brayley G. Resolution 64 meters per pixel. [NASA/GSFC/Arizona State University]. |
Brayley G is most likely a volcanic vent since it is has no elevated rim, is oblong in shape (not circular), and has no ejecta blanket. There are also concentric lines on the inside edge of Brayley G, which may be evidence of concentric faults, left by the partial collapse of the vent. Some depressions may also be formed by the collapse of a sublunarean cavity, such as an drained lava tube.
Explore the entire NAC mosaic, HERE.
Related Posts:
Tuesday, January 24, 2012
Failed skylights of Copernicus
 |
| More than mere melt fracture, a narrow skylight among myriad melt fractures in the chaotic interior of the familiar nearside landmark Copernicus, at a resolution of 40 centimeters per pixel from 25.4 kilometers, August 18, 2011. LROC Narrow Angle Camera observation M168333206L; illumination from the southwest (bottom left) of directly overhead, angle of incidence 38.23° [NASA/GSFC/Arizona State University]. |
Lunar Pioneer
The LROC targeting team had already extensively mapped the interior of Copernicus before the brief period last August when the low point in the LRO polar orbit was reduced by half, sometimes below 25 kilometers. Copernicus might be the most photographed lunar crater after Tycho. Both of these relatively young impact craters are difficult to miss in any view of a waxing Moon seen from Earth. Both craters center on extensive and bright ray systems, and Tycho's being the youngest of the two can be picked out with the naked eye.
Copernicus, though larger than Tycho, seems less intense, almost smudged, and, indeed, it is more faded a more along in years, nearly old enough for the inevitable effects of space weathering to have gardened its face with optical maturity.
 |
| The interior, slumped terraced walls, rim and some of the ejecta blanket of Copernicus as seen in one of the very first LROC Wide Angle Camera (WAC) mosaics released by Arizona State University in early 2010. At its roughly 800 million year age Copernicus, namesake of the "revolutionary" polish astronomer Nicolas Copernic (1473-1543), has lent its name to the Copernican Age on the lunar timescale, that relatively recent and relatively sparse period of bombardment. Its interior is flatter in the north than at the south and features three central peaks. A bifurcated pattern to its rays system and topography has led some to speculate at least two progenitors of nearly equal size were involved in this impact event [NASA/GSFC/Arizona State University]. |
As LROC team member James Ashley was spotlighting the melt fractures of Jackson crater earlier this month we were already performing a survey of the same features on the floor of Copernicus, particularly within the crater's north-central and "more featureless" interior. The melt fractures within Copernicus seem more extensively gardened, and may have formed in a somewhat different way than those at Jackson. At Copernicus there seems to have been, or still may be, voids under the impact melt, and some evidence of what may be bubbling, places that seem to be half-submerged solid rubble on the floor of Tycho, for example, may be place where gases were trapped for a time, escaping after the impact melt had rapidly cooled and solidified.
 | |
| The north central floor of Copernicus only seems less distinctive than the jumbled topography of its surroundings. Barely visible in this LROC WAC monochrome (643 nm) image is a web of fractures and channels throughout the most level terrain above. A 35 km-wide field of view from LROC WAC observation M147109260C, orbit 6813, December 16, 2010; resolution 60.3 meters per pixel at an incidence angle of 78° from 43.13 kilometers [NASA/GSFC/Arizona State University]. |
 |
| Both the north and south ends of this 42 meter-wide exposed fracture on the floor of Copernicus are nearly buried or are not quite as wide as this section. While its tempting to see the western side as an overhang, and despite the apparent differences in the opposing edges, the exposed rift is likely only slightly deeper and more shadowed. There is evidence enough for voids under the floor of Copernicus but the more obvious clues have been pulverized by space weathering and moon quakes since the crater's formation. LROC NAC observation M157730473L, orbit 8379, April 18, 2011; angle of incidence 24.32° on a field of view 270 meters wide at a resolution of 0.47 meters from 37.85 kilometers [NASA/GSFC/Arizona State University]. |
 |
| Is this 300 meter-wide feature on the floor of Copernicus a crater, a void shaken to collapse or a little of both? Apparent layering in rapidly cooling impact melt may be a result of differing arrival times of the melt. LROC NAC M168333260L [NASA/GSFC/Arizona State University]. |
 |
| The area of interest on the floor of Copernicus is distinguished by its melt fractures, many obvious and others mysterious. The traces of these fractures are often marked with pits, their openings too shadowed or narrow to measure - even discovering whether any are really open at all and what may lay below awaiting future exploration. Between the two "pits" appears to be a spot long collapsed - but what if anything actually collapsed? Also from LROC NAC M168333206L [NASA/GSFC/Arizona State University]. |
Friday, January 20, 2012
LROC: Shadows in Egede A
 |
| A field of boulders casts long shadows on the south wall of northern mid-latitude crater Egede A. Illumination from south-southwest at a 54.94° angle of incidence. Field of view is roughly 400 meters across. LROC Narrow Angle Camera (NAC) observation M122137079L, LRO orbit 3135, March 2, 2010; resolution 0.49 meters from 42.45 kilometers. View the full size LROC Featured Image HERE [NASA/GSFC/Arizona State University]. |
LROC News System
As on Earth, that 'golden time' just before the sun dips below the western horizon produces spectacular shadow effects on the Moon, dramatically accentuating perceived surface roughness. Because the Moon has no atmosphere, its shadows are very sharply defined and the contrast between illuminated and shadowed areas is high. The Apollo astronauts often reported difficulty in judging distances to objects because without a hazy or dust-filled atmosphere to 'soften' the view, distant objects looked very similar to objects that were close up. Shadows are useful to planetary scientists doing remote sensing investigations because their length can help us determine the size of the object casting the shadow.
For example, here we see a family of boulders resting on the inner slope of Egede A crater (51.56°N, 10.45°E). Were this a horizontal surface, the shadow length of the largest boulder in the featured image would indicate its height to be approximately 61 m. The calculation is made by knowing the solar incidence angle and using a bit of high school trigonometry. Actually, however, the surface is not horizontal -- an 'early sunset' is produced for these boulders by the sloping crater wall, effectively exaggerating the boulder's height. Therefore the true height of this boulder is something less than 61 m. That means our sun angle is wrong for producing an accurate boulder size estimate. This also means that we would have to know the angle of the sloping crater wall in combination with the sun angle and shadow length to make our calculation. Planetary sciences teaches us to be cautious in our interpretations of what we think we see. Can you think of a way to determine the slope of the crater wall?
 |
| Yellow square shows the field of view of the Featured Image, near the rim of Egede A in the context of the full NAC M159080552L frame, a field of view approximately 2.5 kilometers wide [NASA/GSFC/Arizona State University]. |
Imagine that you're standing on the rim of this crater. The sun would still be relatively high above the horizon. Note how the surface beyond the crater in the context image below is in full sunlight. High overhead is the Earth, looking four times the diameter that the Moon does in our Earth sky. If you then held your hand up to block the sun, the rest of the heavens would be raven black and filled with stars. All your favorite constellations would be recognizable, just as if you were back on Earth, with no visible change in their positions relative to each other -- the distance between the Earth and the Moon simply isn't great enough to register a visible shift among star patterns. You had better find some shelter soon, because it will get very cold here when the sun finally sets!
 |
| Egede A in temporal context, seen here through the LROC Wide Angle Camera (WAC) in a monochrome (604 nm) mosaic stitched from observations swept up in orbits 3132 and 3134, orbital passes immediately before and after the the Featured Image (yellow box) was captured, March 2, 2010. LROC WAC observations M122130239C and M122143802C, with an average resolution of 59.9 meters per pixel from 42.03 kilometers altitude [NASA/GSFC/Arizona State University]. |
Note the faintly visible, light-colored ejecta pattern surrounding Egede A in the image below. This shows it to be a relatively young impact feature. The WNW-ESE trending crater chains to the north and south of Egede A are secondary impacts produced by ejecta from a much larger impact beyond the frame.
 |
| LROC WAC mosaic context image, showing greater relief in long shadows nearer to a true sunset. Note the trails of secondary craters and the outer edge of the ejecta blanket of the far older Aristoteles crater whose center is more than 120 kilometers away. Field of view is about 78 kilometers. View the larger LROC context image HERE [NASA/GSFC/Arizona State University]. |
 |
| Using a modest telescope (or Google Earth, or NASA's ILIADS application), if you find the Alpine Valley (Vallis Alps), the well-known spectacular fracture fault radiant northeast from Mare Imbrium, you can find Egede A. The crater is directly on the opposite end of a line running through the valley from the huge basin [NASA/ILIADS/ASU]. |
LROC Melt fractures in Jackson crater
 |
| Fractures can be seen in profuse abundance on the Jackson crater melt pond surface. Illumination from west, a field of view roughly 700 meters across swept up at an incidence angle of 71.13° LROC Narrow Angle Camera (NAC) observation M118560367L, LRO orbit 2606, January 19, 2010; resolution 0.84 meters from 52.97 kilometers altitude. View the full-size Featured Image HERE [NASA/GSFC /Arizona State University]. |
LROC News System
As molten rock cools, it shrinks and often cracks. In this case of impact melt ponded within the Jackson crater floor (22.18°N, 197.24°E), the cracking rate was so high that unfractured melt is almost more of an exception than a rule!
Radial and divergent patterns can be seen among the fracture sets that tell a story of the cooling history. The context image below shows a portion of their wider distribution.
 |
| As context for the January 18, 2012 LROC Featured Image (field of view near where the impact melt inundating the crater floor emerges from eastern wall slump; the white box) a long view north and up the steep northeastern wall, nearly to the rim, courtesy of the digital elevation model combined in Google Earth [NASA/USGS/ASU/JAXA/Google]. |
 |
| Overhead context for Featured Image, a field of view roughly 2.5 kilometers across from the wider LROC frame.View the full-size LROC context image HERE [NASA/GSFC/Arizona State University]. |
 |
| Further context, from 100 kilometers altitude, this square crop from a highly detailed HDTV still frame was captured by Japan's lunar orbiter SELENE-1 (Kaguya) in 2009 [JAXA/NHK/SELENE]. |
Ed Note: In a way opposite and contributing to the low optical visibility of the vast majority of similarly sized craters in the farside Highlands, Jackson is easier for the eye to see than most. Like Tycho on the nearside, there are a lot of craters of similar size and origin everywhere on the Moon. The difference is age. Like Tycho, the ray system of Jackson (and the materials its progenitor impact threw out) shows Jackson's "optical immaturity." To illustrate, below are two representations of the farside quadrant with the highest of the Highlands scoured by the Jackson impact, likely less than a half billion years ago.
 | ||
| Jackson stands out in this global montage of Clementine (1994) Ultra-Violet/Visible (UVVIS) wavelength photography designed to better map the Moon's albedo, more than a decade ago. Similar craters, basins and the Moon's highest elevations are nearly invisible [NASA/USGS/DOD]. |
 |
| A white arrow is needed to designate Jackson out from the pocked highlands and several otherwise invisible basins stand out with exceptional clarity in this view of nearly the same terrain as a representation of differences in elevation from the LROC Global Digital Terrain Model, developed using LROC Wide Angle Camera survey photography [NASA/GSFC/Arizona State University]. |
Wednesday, January 18, 2012
LROC: Debris flows in Gardner crater
 |
| Base of an avalanche flow at the contact between the east-southeast wall and floor of Gardner crater (17.73°N, 33.81°E), full 0.49 meter per pixel resolution section from LROC Featured Image released January 17, 2012. LROC Narrow Angle Camera (NAC) observation M121987140R, orbit 3111, February 28, 2010; altitude 43.37km, incidence angle 32.75° [NASA/GSFC/Arizona State University]. |
 |
| Full width of the LROC Featured Image, a field of view approximately 800 meters wide. View the full-size (2000 x 2000) LROC Featured Image HERE [NASA/GSFC/Arizona State University]. |
James Ashley
LROC News System
Among the most visually spectacular revelations of the Narrow Angle Camera are the variety of landforms showing the many ways that debris flows interact with their landscapes. Like a braided stream, these dry flows of pulverized rock twist and turn their way down the slopes of Gardner crater (17.7°N, 33.8°E) until they come to rest on the crater floor. Gardner is located within the boundary highlands separating Mare Tranquillitatis and Mare Serenitatis. Visible are signs of sheering within the flows as some portions met with enough frictional resistance to cease flowing, while other portions continued down the slope. Imagine this surging wall of fluidized rock plummeting down the crater wall and out onto the floor shortly after the impact excavated the main crater. It would have been a jaw-dropping sight to behold!
 |
| LROC Wide Angle Camera (WAC) 60 meter per pixel monochrome (604 nm) mosaic showing the immediate vicinity of Gardner and it's steep walls. The NAC observation focuses on the contact between floor and east-southeastern wall, an almost 2000 meters drop in elevation from the crater rim, and where the local sunrise on May 21, 2010 had just occurred [NASA/GSFC/Arizona State University]. |
The context image below shows Mare Tranquillitatis basalt deposits visible in the margins surrounding the narrow region of higher terrain where Gardner crater is located. Nearby Maraldi crater (northeast of Gardner) has been filled with similar deposits.
 |
| LROC WAC mosaic context image from the LROC QuickMap (125 meter resolution) shows the full 18 km-diameter Gardner crater and Maraldi to the northeast. [NASA/GSFC/Arizona State University]. |
Related Posts:
Lunar Landslides
Tendrils in Reiner Crater
Layering in Messier A
Saturday, January 14, 2012
Shadowed fluffy lunar frost detected in starlight
 |
| LRO (in this case the LOLA imaging team) is slowly but certainly stripping away the shadows from the permanently shadowed regions of the Moon. The differences between the water-supporting natures of the rocks deep in the shadowed southern craters Haworth and Shoemaker has been better explained by data collected by LRO's LAMP instrument. From Earth, seen here from a Kaguya HDTV still shot from nearly the same angle in 2008, the shadowed region between the nearside rim of South Pole Aitken basin and 10 km-wide Shackleton (which supports the Moon's south pole on it's rim) can only be measured through "the notch" between Malapert massif on the left and the lofty "Leibnitz beta" massif on the right [NASA/JAXA/LMMP/ILIADS] |
San Antonio New maps produced by the Lyman Alpha Mapping Project (LAMP) aboard NASA's Lunar Reconnaissance Orbiter (LRO) reveal features at the Moon's north and south poles in regions that lie in perpetual darkness. Developed by the Southwest Research Institute (SwRI), the LAMP instrument is sensitive on dim "starlight," specifically the band of electro-magnetic frequencies emitted when hydrogen (which usually travels in pairs) is reduced to a single atom, usually when encountering other forms of radiation.
This Ly-α (Lyman-alpha) spectral line is peculiar to neutral hydrogen, the most basic and abundant element in the universe, is produced by light with a wavelength of 121.4 nm, a frequency below the narrow band of optical frequencies visible to the naked eye. By gathering data revealed by this all-pervasive indirect starlight LAMP can peer into so-called "permanently shadowed regions" (PSRs).
In repeated passes over the lunar poles using this method researchers have able to determine the presence of very fine structure, such as the likely porosity of lunar surface rock or the most likely textures of water frost in super-cold volatile traps, in permanent shadow from the Sun, and only in those places on the Moon not overwhelmed by direct or immediately indirect sunlight.
The LAMP maps show that many PSRs are darker at far-ultraviolet wavelengths and redder than nearby surface areas that receive sunlight. The darker regions are consistent with large surface porosities — indicating "fluffy" soils — while the reddening is consistent with the presence of water frost on the surface.
"Our results suggest there could be as much as 1 to 2 percent water frost in some permanently shadowed soils," says author Dr. Randy Gladstone, an Institute scientist in the SwRI Space Science and Engineering Division. "This is unexpected because naturally occurring interplanetary Lyman-alpha was thought to destroy any water frost before it could accumulate."
The LAMP team estimates that the loss of water frost is about 16 times slower than previously believed. In addition, the accumulation of water frost is also likely to be highly dependent on local conditions, such as temperature, thermal cycling and even geologically recent "impact gardening" in which micrometeoroid impacts redistribute the location and depth of volatile compounds.
 |
| Lyman-alpha albedo maps for greater south polar region from the first year of LAMP night-side observations. Initial studies were focused on those areas above 80°N. The white square is the area highlighted in a recent paper comparing what's been discovered about the big differences between the interiors of permanently shadowed neighbors Haworth and Shoemaker craters. "Calibrated photon events" accumulated month by month and divided by model-based illumination baselines show "generally, we find good agreement between UV-dark regions and the coldest shaded craters revealed by the LRO Diviner instrument." Identifying the cause of this albedo darkening required spectral analysis but the likeliest explanation included either the presence of "UV-absorbing volatiles at the surface" and/or "a change in surface properties (e.g., roughness or porosities) at these interesting locations." [Retherford et al., Lunar and Planetary Sciences Conference, (2011)]. |
Finding water frost at these new locations adds to a rapidly improving understanding of the Moon's water and related species, as discovered by three other space missions through near-infrared emissions observations and found buried within the Cabeus crater by the LCROSS impactor roughly two years ago. During LRO's nominal exploration mission, LAMP added to the LCROSS results by measuring hydrogen, mercury and other volatile gases ejected along with the water from the permanently shaded soils of the Moon's Cabeus crater.
"An even more unexpected finding is that LAMP's technique for measuring the lunar Lyman-alpha albedo indicates higher surface porosities within PSRs, and supports the long-postulated presence of tenuous 'fairy-castle' like arrangements of surface grains in the PSR soils," says co-author Dr. Kurt Retherford, a senior research scientist also in SwRI's Space Science and Engineering Division.
Comparisons with future LAMP maps created using data gathered from the Moon's day side will prove helpful for revealing more about the presence of water frost, as well as the surface porosities of the darker surface features observed. The LAMP team is also eager to apply the Lyman-alpha technique elsewhere on the Moon and on other solar system objects such as Mercury.
 |
| No longer terra incognitia, the permanently shadowed interiors and area surrounding the southern polar craters Haworth and Shoemaker have had their elevation unveiled in precise detail, seen here in laser altimetry collected over two years and several thousand polar orbits [NASA/GSFC/LOLA]. |
LRO's findings are expected to be valuable to the future consideration of a permanent Moon base. The permanently shadowed regions of the Moon are revealing themselves to be some of the most exotic places in the solar system, well worthy of future exploration, says Retherford. Any discovery of water frost and other resources in the area also could reduce the need to transport resources from Earth to a base at the pole.
The paper, "Far-Ultraviolet Reflectance Properties of the Moon's Permanently Shadowed Regions," by G.R. Gladstone, K.D. Retherford, A.F. Egan, D.E. Kaufmann, P.F. Miles, et al., was published in the Jan. 7 issue of the Journal of Geophysical Research. LAMP's principal investigator is Dr. Alan Stern, associate vice president of the SwRI Space Science and Engineering Division.
Subscribe to:
Posts (Atom)