The Moon's south pole, as see by the Lunar Reconnaissance Orbier. Credit: NASA/GSFC/Arizona State University.
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No, this is not a wheel of moldy Swiss Cheese. It’s an illumination map of the South Pole of the Moon. There are some areas on the poles of the Moon, particularly the interior of craters, that lie in permanent shadow while other areas remain sunlit for the majority of the year. This image was taken by the Lunar Reconnaissance Orbiter Camera, which has a primary objective of unambiguously identifying these regions. This composite image contains over 1,700 images taken of the same area by the LROC Wide Angle Camera (WAC) over a six month period, which works out to six lunar days.
Here’s how the LROC team described how they created the image:
“Each image was map projected and converted to a binary image (if the ground was illuminated that pixel was set to one, and if shadowed zero) to differentiate between sunlit and shadowed regions. All the binary images were then stacked, and then for each pixel it was determined what percentage of the time during six months that spot was illuminated. Presto – an illumination map! The LROC team is making daily (which is about 28 Earth days) and yearly illumination maps for both poles. Such maps will provide the foundation for planning future robotic and human missions to the poles.”
Sketches made by the Apollo 17 crew of rays created by lofted lunar dust. Credit: NASA
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There are times when Moon appears to have a tenuous atmosphere of moving dust particles that are leaping up from and falling back to the Moon’s surface. First seen during the Surveyor and Apollo eras, these observations were completely unexpected, and scientists today are still trying to understand this phenomenon.
The first indication that something strange was going on with the lunar surface was in the 1960’s when cameras on the Surveyor spacecraft pointing towards the western horizon noticed a brighter hovering cloud that persisted for several hours.
“There are many other bits and pieces of observations of this kind,” said Dr. Mihaly Horanyi from the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics. “For example, the astronauts in the Apollo command modules that stayed in orbit about the Moon were hoping to take images of the dark sky, but of course there is scattered light from the dust in interplanetary space. But the brightness also appeared to follow the lunar surface, indicating that somehow dust is coming off the surface of the Moon.”
While astronauts from Apollo 8, 10, and 15 all reported such dust clouds, Apollo 17 in 1972 repeatedly saw and sketched what they called “bands,” “streamers” or “twilight rays” for about 10 seconds before lunar sunrise or lunar sunset.
Adding to the mystery, also on Apollo 17 was a dust detector placed on the surface by the astronauts, the Lunar Ejecta and Meteorite experiment, which was supposed to measure the high speed impacts of micrometeorites hitting the moon.
An Apollo 17 astronaut digs in the lunar regolith to study the mechanical behavior of moon dust. Credit: NAS
“Instead the measurements showed an increase of particle fluxes that went up a hundred fold when day turned to night and night turned into day at that location on the Moon,” Horanyi said.
“Every single one of these measurements has an alternate explanation somehow. But it seems that the whole body of these observations is best explained by recognizing that dust — even on an airless body — can move around and come to life.”
Even thought the Moon has no atmosphere, Horanyi said other processes that are likely related to the plasma and radiation environment of the Moon, “the electro-dynamic processes of the near surface lunar environment that can have strong enough electric fields and the surface can have enough electrostatic charges that can break the dust free and somehow shuffle it or move it around the surface.”
In other words, electrostatic charging of the lunar surface causes the dust to levitate, precipitated – somehow – by changes in sunlight.
Horanyi said this type of thing has been seen on other airless bodies, like on Mercury, comets and asteroids.
“For example, the near-landing on the asteroid Eros,”Horanyi said, “people noticed that the bottom of the craters are filled with fine dust, and there is not enough atmosphere, and certainly the body is too small have asteroid shakes – the asteroid version of earthquakes — so the possible transport that would trap or make dust pile up in some regions and move it from others, is most likely a plasma effect.”
Horanyi and other scientists have done lab experiments to try and replicate the lunar environment to see if a dust transport takes place.
“For the first set of experiments, imagine just a piece of surface with dust particles on it, and we shine light on this surface,” he said, “so that half is illuminated, half is not, pretending that there is a terminator region, that the sun is set on one side and is still shining light on the other. When you shine light on the surface with properties that are appropriate, you can emit photo electrons, but you only emit electrons from the lit side, and some of those electrons land on the dark side, — you have a positive charge surplus on the lit and a negative charge pile-up on the night side. Across a couple of millimeters you can easily generate a potential difference of maybe a watt, or a handful of watts, which translates actually as a small-scale, but incredibly strong electric fields. This could be like a kilowatt over a meter. But of course, it only exists over a sharp boundary, and that sharp boundary may be the key to understanding how you get dust moving to begin with.”
Horanyi said in the transient region where boundaries match up – lit and dark boundaries, or boundaries between where the surface is exposed to a plasma and where it is not – those sharp transitions could actually overcome adhesion between dust and the rest of the surface and start moving.
“And that’s where the story gets really interesting,” he said.
Hopefully, a new mission called LADEE (Lunar Atmosphere and Dust Environment Explorer) can help explain this mystery. It is slated to launch in 2013 and fly in low lunar orbit, as close to the surface as 30-50 km. Since NASA may not be sending astronaut to the Moon anytime soon, LADEE’s mission may now be a little different than previously thought, but it still has some important science to conduct.
It will carry three instruments, an infrared imager, a neutral mass spectrometer and a dust detector, which Horanyi is helping to build.
“That hopefully will be capable of measuring tiny, tiny, small particles that people argue are lofted from the surface,” Horanyis said. “And we hope that in combination these instruments might put an end to this argument that we’ve had since the early 1970’s whether dust is really actively transported and shuffled around on the lunar surface or not.”
Both lunar and solar eclipses can only occur when the Earth, Sun and Moon are directly aligned… and that alignment is about to happen just four days before Christmas! While the winter treat of totality will lend itself to North America, many other parts of the world will be able to enjoy a partial eclipse as well. Just remember your time zones and I’ll post specific times and locations just a little closer to the date. Right now, let’s learn more!
What is a partial eclipse or totality? When the Earth’s shadow engulfs the Moon, it is a lunar eclipse which occurs in two phases. The outer shadow cone is called the penumbra and the dark, inner shadow is called the umbra. A round body, such as a planet, casts a shadow “cone” through space. When it’s at Earth, the cone is widest at 13,000 kilometers in diameter, yet by the time it reaches the Moon it has narrowed to only 9,200 kilometers. Considering the distance to the Moon is 384,401 kilometers, that’s hitting a very narrow corridor in astronomical terms!
As a rule of thumb, remember that the Moon moves about its own diameter each hour, so the very beginning of a penumbral eclipse will be difficult to notice. Slowly and steadily, the coloration will begin to change and even inexperienced eclipse watchers will notice that something is different. The Moon will never completely disappear as it passes through the Earth’s umbral shadow cone, either. Thanks to our atmosphere bending the sunlight around us, it scatters the light and refracts the signature red and copper coloration we associate with lunar eclipse. Why? Just the small particles in our air – dust and clouds – the shorter wavelengths of light from the Sun are more likely to be scattered (in this case, red) and that’s what we see. Exactly the same reason sunset and sunrise appears to be red! If you’d like to dedicate a portion of your mind to science, then try judging the eclipse coloration on the Danjon scale. It was was devised by Andre Danjon for rating the overall darkness of lunar eclipses:
L=0: Very dark eclipse. Moon almost invisible, especially at mid-totality.
L=1: Dark Eclipse, gray or brownish in coloration. Details distinguishable only with difficulty.
L=2: Deep red or rust-colored eclipse. Very dark central shadow, while outer edge of umbra is relatively bright
L=3: Brick-red eclipse. Umbral shadow usually has a bright or yellow rim.
L=4: Very bright copper-red or orange eclipse. Umbral shadow is bluish and has a very bright rim.
Now we know what to plan for! Time to get your winter gear ready. Photographing or video taping an eclipse is easy – but remember if you live where it is very cold that your batteries will expire fast – so keep an extra set in a warm place next to your body.
Be sure to check back for specific times and locations here at UT on December 20th… and tell your family and friends about the very special Christmas present that’s coming your way!
Eclipse Images Courtesy of Doug Murray (top), Tom Ruen (bottom) and NASA (center illustration). We thank you!
A huge impact may have formed the Moon, but other large impacts could have determined the makeup of Earth and other planetary bodies. Image Credit: Joe Tucciarone
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One of the fundamental problems in planetary science is trying to determine how planetary bodies in the inner solar system formed and evolved. A new computer model suggests that huge objects – some as big as large Kuiper Belt Objects like Pluto and Eris — likely pummeled the Earth, Moon and Mars during the late stages of planetary formation, bringing heavy metals to the planetary surfaces. This model – created by various researchers from across the NASA Lunar Science Institute — surprisingly addresses many different puzzles across the Solar System, such as how Earth could retain metal-loving, elements like gold and platinum found in its mantle, how the interior of the Moon could actually be wet, and the strange distribution in the sizes of asteroids.
“Most of the evidence of what happened during the late stages of planetary formation has been erased over time,” said Bill Bottke from the Southwest Research Institute, who led the research team. “The trail we’ve been tracking on these worlds is pretty cold and to be able to dig more information out of what we have and be able answer some long standing problems is pretty exciting.”
Bottke told Universe Today that the story this new model tells “is not as complicated as it looks at first glance,” he said. “It includes a lot of concepts together, and some of the concepts have actually been around for awhile.”
Bottke and his team have published their results in the journal Science.
The researchers started with the widely accepted theory of how our Moon was created by a giant impact between the early Earth and another Mars-sized planetary body. “This was the most traumatic event the Earth probably ever went through, and that was the time when presumably the Earth and Moon both formed their cores,” Bottke said.
The heavy iron fell to the center of the two bodies, and so-called highly siderophile, or metal-loving, elements such as rhenium, osmium platinum, palladium, and gold should have followed the iron and other metals to the core in the aftermath of the Moon-forming event, leaving the rocky crusts and mantles of these bodies void of these elements.
“These elements love to follow the metal,” Bottke said, “so if the metal is draining to the core, these elements would want to drain with them. So if this is right, what we would expect that rocks derived from our mantle should have almost no highly siderophile elements, maybe 10 to the minus 5th level or so. But surprisingly, that is not what we see. They are only less abundant by a factor of less than 200, compared to what we would expect, a factor of 100,000 or so.”
Bottke said this problem has been argued about since the 1970’s, with various suggestions on how to answer the problem.
“The most viable answer is that after the Moon forming impact took place, there were also other things that hit the Earth during the late stages of planet formation, objects that were smaller, and these smaller objects replenished these elements and gave us the abundance we see today. This is what we refer to as late accretion,” he said.
On the Moon, the same thing was happening. But there was a problem with this scenario. The ratio of these elements on the Earth compared with rocks on the Moon is about 1000 to 1.
“The gravitational cross section of the Earth is about 20 times that of the Moon,” Bottke said, “So for every object that hit the Moon, about twenty should have hit the Earth. And if late accretion delivered these elements, you should have about a 20 to 1 ratio. But that is not what we see—we see a 1000 to 1 ratio.”
Bottke – a planetary dynamacist — discussed this with colleague David Nesvorny, also from SWRI, as well as geophysical-geochemical modelers, such as Richard Walker from the University of Maryland, James Day from the University of Maryland, and Linda Elkins-Tanton from the Massachusetts Institute of Technology.
They came up with a computer model that seemed to provide an answer.
“By playing roulette with these objects, I found that very often the Earth was getting hit by huge impactors that the Moon would never see,” Bottke said. “This result suggests that the things hitting the Earth and Moon at the end of the planet formation period was dominated by very large objects.”
The model predicted that the largest of the late impactors on Earth, at 2,400 – 3,200 km (1,500-2,000 miles) in diameter, while those for the Moon, at approximately 240 – 320 km.
Bottke called that a “cute” result – but they needed more supporting evidence. So, they took a look at the last surviving population of the things that built the planets, the inner asteroid belt. “You find large asteroids like Ceres, Vesta and Pallas” Bottke said, so there are the large ones at 500 to 900 km, but then your next largest asteroids are only about 250 km. This matched up with the sizes that our model came up with,” in which no asteroids with “in-between” sizes are observed in this region.
Maps of Mars' global topography. Credit: NASA
Next, they looked at Mars, which has some very large impact basins which are probably left over from the days of when the planet formed, including the Borealis Basin, which is so large it likely accounts for the differences in the northern and southern hemispheres on the Red Planet.
“We looked and projected the size of the impactors that would have created those impact basins and we saw the distribution of sizes was very much like what was predicted for the Earth and Moon, and also what is found in the inner asteroid belt.
So all those things together — the theoretical basis, the observational evidence from elements on the Earth and Moon, and impacts on Mars collectively says something about the distribution of sizes of objects towards the end of planetary formation.
And what are the implications?
“We could make predictions for what was hitting the Earth, Moon and Mars at that time, and they line up with what we see on the surfaces,” Bottke said. “On Mars we can play a game of what is the biggest projectiles that should have hit Mars, and it matches up well with the size that big basin that formed on Mars, and also produced the abundances of elements we see there.”
“For the Moon, the biggest impactors would be 250-300 km, which is about the size of the south pole Aiken basin,” Bottke continued. “For the Earth, these big impactors explain why some of these impacts managed to hit the Earth and not all the elements went to the core of the Earth.”
Bottke said that adding to the complications, some of the biggest impacts actually may have plowed through the Earth and actually came out the other side — in a very fragmented state — and rained back down on Earth. “If this is true, this provides a way to spread fragments all the way across the Earth,” he said, “but how the debris gets redistributed around the planetary body is a really interesting question. That part needs a lot more work and is simply at the edge right now of what we can do numerically.”
When it comes to water on the Moon’s interior – which was once thought to be dry, but recent sample measurements, however, suggest that the water content in the lunar mantle is between 200 and several thousand parts per billion — Bottke’s model could also address this issue.
“If true,” the team writes in their paper, “it is possible that the same projectile that delivered most of the Moon’s HSEs may have also have provided it with water….Late accretion provides an alternative explanation in case lunar mantle water cannot migrate from the post–giant impact Earth to a growing Moon through a hot and largely vaporized protolunar disk.”
As to why smaller projectiles hit the Moon as compared to Earth, Bottke said it is just a numbers game. “We start with a population which has a certain number of big things, middle sized things and small things,” he said. “And we randomly choose projectiles from that population and for every one big guy that hits the Moon, 20 hit the Earth. And we play that game, and if the number of projectiles is limited, if the Moon only gets hit once or twice from this population, that means the Earth gets hit 20-30 times, that is enough to give us – on most occasions – what we see.”
Bottke said this research gave him a chance to work with geochemists, “who have all sorts of interesting things to say which help constrain the processes that brought about planet formation. The problem is that sometimes they have great information but they don’t have a dynamical process that can work. So by working together I think we were able to come up with some interesting results.”
“The most exciting thing for me is that we should be able to use these abundances that we have on the Earth, Moon and Mars to really tell the story about planet formation,” Bottke said.
The White House is looking into ways to reduce the number of astronauts employed by the U.S. Image Credit: NASA
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CAPE CANAVERAL – When we think of NASA, the first thing that most Americans picture is the men and women of the astronaut corps. It turns out that the White House has been thinking about them as well – as maybe something that might need to be cut down. The Obama administration has requested a 10-month long study be held to determine the appropriate ‘size’ of NASA’s astronaut corps.
There are only two (and a potential third) shuttle flights remaining on the current manifest.
Right now, NASA has 64 astronauts, which some might consider a bit much if very few will be flying to space. However, if three NASA astronauts are part of each 6-member, 6-month Expedition on the International Space Station from 2011-2017 (the projected time period when NASA will be unable to launch their own astronauts) that still is 36 astronauts with a mission to space.
But the proposal to cut NASA’s astronaut corps comes on the heels of numerous successive cuts that the space agency has endured over the past year. Many view the loss of the corps as one more blow to both spaceflight experience as well as national prestige.
The White House hopes that commercial space companies such as SpaceX, which is slated to launch the second of its Falcon 9 rockets sometime this week, will emerge to fill the void created by NASA’s absence. However, to date, none of these firms have launched an astronaut into orbit. During the interim, and until NASA can build its own heavy lift vehicle, the US space agency is relying on — and paying — the Russians to bring US astronauts to the ISS via the Soyuz.
There has never been more than 150 astronauts at any given time (the most ever was 149 back in 2000). Although most Americans assume that NASA has a massive budget, for what the agency does and provides, it is incredibly small, about one-seventh of a penny out of every tax dollar helps to pay for the ISS, the shuttle program, the probes and rovers to the planets and the astronaut’s salaries. The agency’s budget is currently $18.7 billion a year. The 47 civilian astronauts earn between $65,000 and $100,000 annually, with the remaining military astronauts being paid through the Department of Defense (DoD) which NASA reimburses.
The National Academies is the organization that will conduct the review of the astronaut corps and they are leaving no stone unturned, even the T-38 ‘Talon’ jets that the astronauts fly in, are coming under scrutiny. These jets are not state-of-the-art fighters, but rather training aircraft that date back to the beginning of the space age. These planes, equipment and facilities used to train astronauts and the current number of astronauts will all be reviewed.
“I still don’t know how many folks are in the queue and were not selected for shuttle, ” said two-time shuttle astronaut Robert Springer. “If you are in the program and there is little or no chance to fly in the next 4-8 years that’s too bad, but it’s not the first time this has happened, and if you like the environment, working with some of the greatest people in the business, it can lead to challenging working on the next great enterprise.”
But some have a different idea of how NASA could cut costs.
“You know, if Obama really wanted to cut waste at NASA – he’d start with headquarters,” said a long-time NASA employee who requested to remain anonymous for fear of retribution. “That place is stocked with GS-15s – who really don’t do much of anything!” He said referring to the government pay grade of many of the high-level officials that work at NASA’s headquarters in Washington D.C.
Seeking to detect mysterious, ultra-high-energy neutrinos from distant regions of space, a team of astronomers used the Moon as part of an innovative telescope system for the search. Their work gave new insight on the possible origin of the elusive subatomic particles and points the way to opening a new view of the Universe in the future.
The team used special-purpose electronic equipment brought to the National Science Foundation’s Very Large Array (VLA) radio telescope, and took advantage of new, more-sensitive radio receivers installed as part of the Expanded VLA (EVLA) project. Prior to their observations, they tested their system by flying a small, specialized transmitter over the VLA in a helium balloon.
In 200 hours of observations, Ted Jaeger of the University of Iowa and the Naval Research Laboratory, and Robert Mutel and Kenneth Gayley of the University of Iowa did not detect any of the ultra-high-energy neutrinos they sought. This lack of detection placed a new limit on the amount of such particles arriving from space, and cast doubt on some theoretical models for how those neutrinos are produced.
Neutrinos are fast-moving subatomic particles with no electrical charge that readily pass unimpeded through ordinary matter. Though plentiful in the Universe, they are notoriously difficult to detect. Experiments to detect neutrinos from the Sun and supernova explosions have used large volumes of material such as water or chlorine to capture the rare interactions of the particles with ordinary matter.
The ultra-high-energy neutrinos the astronomers sought are postulated to be produced by the energetic, black-hole-powered cores of distant galaxies; massive stellar explosions; annihilation of dark matter; cosmic-ray particles interacting with photons of the Cosmic Microwave Background; tears in the fabric of space-time; and collisions of the ultra-high-energy neutrinos with lower-energy neutrinos left over from the Big Bang.
Radio telescopes can’t detect neutrinos, but the scientists pointed sets of VLA antennas around the edge of the Moon in hopes of seeing brief bursts of radio waves emitted when the neutrinos they sought passed through the Moon and interacted with lunar material. Such interactions, they calculated, should send the radio bursts toward Earth. This technique was first used in 1995 and has been used several times since then, with no detections recorded. The latest VLA observations have been the most sensitive yet done.
“Our observations have set a new upper limit — the lowest yet — for the amount of the type of neutrinos we sought,” Mutel said. “This limit eliminates some models that proposed bursts of these neutrinos coming from the halo of the Milky Way Galaxy,” he added. To test other models, the scientists said, will require observations with more sensitivity.
“Some of the techniques we developed for these observations can be adapted to the next generation of radio telescopes and assist in more-sensitive searches later,” Mutel said. “When we develop the ability to detect these particles, we will open a new window for observing the Universe and advancing our understanding of basic astrophysics,” he said.
The scientists reported their work in the December edition of the journal Astroparticle Physics.
Many objects in the solar system have strong magnetic fields which deflect the charged particles of the solar wind, creating a bubble known as the magnetosphere. On Earth, this protects us from some of the more harmful solar rays and diverts them to create beautiful aurorae. Similar displays have been found to occur on the gas giants. However, many other objects in our solar system lack the ability to produce these effects, either because they don’t have a strong magnetic field (such as Venus), or an atmosphere with which the charged particles can interact (such as Mercury).
Although the moon lacks both of these, a new study has found that the moon may still produce localized “mini-magnetospheres”. The team responsible for this discovery is an international team composed of astronomers from Sweden, India, Switzerland, and Japan. It is based on observations from the Chandrayaan-1 spacecraft produced and launched by the Indian Space Research Organisation (ISRO).
Using this satellite, the team was mapping the density of backscattered hydrogen atoms that come from solar wind striking the surface and being reflected. Under normal conditions, 16-20% of incoming protons from the solar wind is reflected in this way.
For those excited above 150 electron volts, the team found a region near the Crisium antipode (the region directly opposite the Mare Crisium on the moon). This region was previously discovered to have magnetic anomalies in which the local magnetic field strength reached several hundred nanotesla. The new team found that the result of this was that incoming solar wind was deflected, creating a shielded region some 360 km in diameter surrounded by a “300-km-thick region of enhanced plasma flux that results from the solar wind flowing 23 around the mini-magnetosphere.” Although the flow bunches up, the team finds that the lack of a distinct boundary means that there is not likely to be a bow shock, which would be created as the buildup becomes sufficiently strong to directly interact with additional incoming particles.
Below energies of 100 eV, the phenomenon seems to disappear. The researchers suggest this points to a different formation mechanism. One possibility is that some solar flux breaks through the magnetic barrier and is reflected creating these energies. Another is that, instead of hydrogen nuclei (which composes the majority of the solar wind) this is the product of alpha particles (helium nuclei) or other heavier solar wind ions striking the surface.
Not discussed in the paper is just how valuable such features could be to future astronauts looking to create a base on the moon. While the field is relatively strong for local magnetic fields, it it still around two orders of magnitude weaker than that of Earth’s. Thus, it is unlikely that this effect would be sufficiently strong to protect a base, nor would it provide protection from the x-rays and other dangerous electromagnetic radiation that is provided by an atmosphere.
Instead, this finding poses more in the way of scientific curiosity and can help astronomers map local magnetic fields as well as investigate the solar wind if such mini-magnetospheres are located on other bodies. The authors suggest that similar features be searched for on Mercury and asteroids.
Emily Lakdawalla at the Planetary Society blog unearthed some really cool videos taken by the Chinese Chang’E 2 spacecraft at the Moon. The five engineering videos include Chang’E 2’s solar panel deployment, orbit insertion burn, the first and second orbital trim maneuvers, and low lunar orbit. They are all especially unique in that the video not only includes images from the Moon’s surface, but also the spacecraft itself can be seen, providing a perspective that is not often seen. The video above is of Chang’E 2’s second orbit trim maneuver. Check out Emily’s post to see all five, plus she provides great insights into the video clips, as well.
A self-conscious Moon might ask, “Does my far side look big?” To which lunar scientists would have to reply in the affirmative. They have long known there is a bulge on the Moon’s far side, a thick region of the lunar crust which underlies the farside highlands. But why that bulge is there has been a mystery, and the fact that the far side always faces away from Earth hasn’t helped. Now, a group of international scientists have found that perhaps the tidal processes of Jupiter’s icy moon, Europa, can provide a clue.
“Europa is a completely different satellite from our moon, but it gave us the idea to look at the process of tidal flexing of the crust over a liquid ocean,” said Ian Garrick-Bethell, the lead author of a new paper that offers an explanation for the lop-sided Moon.
Since the Apollo 15 laser altimeter experiment, scientists have known that a region of the lunar far side highlands is the highest place on the Moon. Additionally, the far side has only highlands and no maria.
Like Europa’s icy crust that sits over an ocean of liquid water, the Moon’s crust once floated on a sub-surface ocean of liquid rock. So, could the same gravitational forces from Jupiter that influence Europa also apply to the Earth’s influence on the early Moon?
Garrick-Bethell, from UC Santa Cruz, and his team found that the shape of the Moon’s bulge can be calculated by looking at the variations in tidal heating as the ancient lunar crust was being torn away from the underlying ocean of liquid magma.
Map of crustal thickness. Credit: Garrick-Bethell, et al.
With Europa in mind, the scientists looked at global topography and gravity data sets of the Moon, trying to determine the possibility of how about 4.4 billion years ago, the gravitational pull of the Earth could have caused tidal flexing and heating of the lunar crust. At the polar regions, where the flexing and heating was greatest, the crust became thinner, while the thickest crust would have formed in the regions in line with the Earth.
To back up their theory, they found that a simple mathematical function — a 2-degree spherical harmonics function — can explain the phenomenon. “What’s interesting is that the form of the mathematical function implies that tides had something to do with the formation of that terrain,” said Garrick-Bethell.
The far side of the Moon, photographed by the crew of Apollo 11 as they circled the Moon in 1969. The large impact basin is Crater 308. Credit: NASA
However, this doesn’t explain why the bulge is now found only on the farside of the Moon. “You would expect to see a bulge on both sides, because tides have a symmetrical effect,” Garrick-Bethell said. “It may be that volcanic activity or other geological processes over the past 4.4 billion years have changed the expression of the bulge on the nearside.”
Garrick-Bethell said his team hopes to continue to do more modeling and calculations to fully describe the far side’s features.
“It’s still not completely clear yet, but we’re starting to chip away at the problem,”he said.
The paper will be published in the November 12, 2010 issue of Science.
(Paper not yet available — we’ll post the link when it goes online).
A lunar crater in stunning detail from the Chang'E 2 orbiter. Credit: CNSA / China Lunar Exploration Program
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China’s space agency released the first images taken by the newest lunar orbiter, Chang’E 2. “The relaying back of the pictures shows that the Chang’e-2 mission is a success,” said Zhang Jiahao, director of the lunar exploration center of the China National Space Administration.
During its expected 6-month mission the orbiter will come within 15km above the surface, with the main mission of looking for potential landing for Chang’E-3, China’s next lunar mission that will send a rover to the Moon’s surface, scheduled for 2013. While all the other images are of Sinus Iridum (Bay of Rainbows), a rough translation of the writing on this top image has something to do with “antarctic,” so its possible this could be a crater near one of the lunar poles.
This 3-D map view of the moon’s Bay of Rainbows was taken by China’s Chang’e 2 lunar probe in October 2010. The mission is China’s second robotic mission to explore the moon. Credit: China Lunar Exploration Program
The data for this 3D image was taken by a the spacecraft’s stereo camera from 18.7 km on Oct. 28, four days after launch. The image has a resolution of 1.3 meters per pixel, more than ten times the resolution of pictures from Chang’E 2’s predecessor, Chang’E 1.
For comparison, NASA’s Lunar Reconnaissance Orbiter has a resolution of about 1 meter.
Sinus Iridum is considered to be one of the candidates for the 2013 lander.
Chang’E 2 will also test “soft landing” technology for the lander, which might mean that either the spacecraft is carrying an impactor or that the spacecraft itself will be crashed into the lunar surface like Chang’E 1.
This photo, taken by China’s Chang’e 2 lunar probe in October 2010, shows a crater in the moon’s Bay of Rainbows. . Credit: China Lunar Exploration ProgramAnother Chang'E 2 image. Credit: Credit: China Lunar Exploration Program
