Earth and Moon from 114 Million Miles.Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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A new image to add to the family photo album! The MESSENGER spacecraft is working its way to enter orbit around Mercury in March of 2011, and while wending its way, took this image of the Earth and Moon, visible in the lower left. When the image was taken in May 2010, MESSENGER was 183 million kilometers (114 million miles) away from Earth. For context, the average separation between the Earth and the Sun is about 150 million kilometers (93 million miles). It’s a thought provoking image (every one of us is in that image!), just like other Earth-Moon photos — Fraser put together a gallery of Earth-Moon images from other worlds, and this one will have to be added. But this image was taken not just for the aesthetics.
This image was taken as part of MESSENGER’s campaign to search for vulcanoids, small rocky objects hypothesized to exist in orbits between Mercury and the Sun. Though no vulcanoids have yet been detected, the MESSENGER spacecraft is in a unique position to look for smaller and fainter vulcanoids than has ever before been possible. MESSENGER’s vulcanoid searches occur near perihelion passages, when the spacecraft’s orbit brings it closest to the Sun. August 17, 2010 was another such perihelion, so if MESSENGER was successful in finding any tiny asteroids lurking close to the Sun, we may hear about it soon.
mages from Moon Zoo showing trails from tumbling boulders in the Montes Alpes/Vallis Alpes region on the Moon. Credit: NASA/LRO/Moon Zoo.
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There’s probably a great story in this image, if only someone was there to witness it as it happened! This is an image from Moon Zoo, the citizen science project from the Zooniverse that asks people to look at images from the Lunar Reconnaissance Orbiter and search for craters, boulders and more. And often, the Zooites find some very interesting features on the Moon, like this one and the ones below that include tracks from rolling, bounding, tumbling and sometimes bouncing boulders. Then the task for the scientists is to figure out what actually happened to get these boulders moving — was it an impact, are the boulder on the bottom of a hill, or was it some other unknown catalyst? As Zooniverse founder Chris Lintott says, “The Moon has its own landscape that is really quite dramatic, so it’s a world well worth exploring.”
LRO image from Moon Zoo.
Why look for tumbling boulders? Moon Zoo scientist Dr. Katie Joy gave this explanation:
“One of the main reasons we are asking Moon Zoo users to search for scars left behind by tumbling boulders is to help support future lunar exploration initiatives. Boulders that have rolled down hillsides from crater walls, or massifs like the Apollo 17 landing site, provide samples of geologic units that may be high up a hillside and thus difficult to access otherwise by a rover or a manned crew vehicle. If mission planning can include traverses to boulders that have rolled down hills, and we can track these boulders back up to the part of hillside from where they have originated, it provides a neat sampling strategy to accessing more geological units than would have been possible otherwise… Thus we hope to use Moon Zoo user data to produce a map of known boulder tracks (and terminal boulders) across the Moon.”
If you want to join in on the fun of looking for mysteries on the Moon, check out Moon Zoo, or the Zooniverse for more citizen science projects where you can get involved in helping scientists do real science.
Hadley Rille, the landing site for Apollo 15. Credit: NASA
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With all the recent news of water on the Moon, a new paper published today in the journal Science may offer a surprise – or it may bring us back to previous assumptions about the Moon. A new analysis of eleven lunar samples from the Apollo missions by Zachary Sharp from the University of New Mexico and his colleagues indicates that when the Moon formed, its interior was essentially dry. While the recent findings of ubiquitous water and hydroxyl on the surface as well as water ice in the lunar poles are not challenged by this new finding, it does dispute — somewhat — two other recent papers that proposed a wetter lunar interior than previously thought. “The recent LCROSS findings were of water on the lunar surface due to cometary impacts, and the ice is from the comets themselves,” Sharp told Universe Today. “We are talking about water that was present in the molten early Moon 4.5 billion years ago.”
The accepted theory of how the Moon formed is that a Mars-sized body slammed into our early Earth, creating a big disk of debris that would ultimately form into the Moon.
Although planetary scientists are still refining models of the Moon’s formation, there is much to suggest a dry Moon. Any water would have been vaporized by the high temperatures generated by the impact and cataclysm that followed, and vapor would have escaped into space. The assumption is that the only way there could be water in the Moon’s interior if is the impactor was especially water-rich, and also if the Moon solidified quickly, which is considered unlikely.
But earlier this year, Francis McCubbin and his team from the Carnegie Institution for Science released their findings of a surprisingly high abundance of water molecules — as high as several thousand parts per million — bound to phosphate minerals within volcanic lunar rocks, which would have formed well beneath the lunar surface and date back several billion years.
Additionally, in 2008, Alberto Saal of Brown University and colleagues found a slightly lower abundance of water in the lunar mantle, but it was significantly higher than the previous estimate of 1 part per billion.
These two findings have been pushing lunar scientists to find possible alternative explanations for the Moon’s formation to account for all the water.
But now, Sharp and his team studied a wide range of lunar basalts and measured the composition of chlorine isotopes. Using gas source mass spectrometry they found a wide range of chlorine isotopes contained in the samples which are 25 times greater than what is found in rocks and minerals from Earth and from meteorites.
Chlorine is very hydrophilic, or attracted to water, and is an extremely sensitive indicator of hydrogen levels. Sharp and his team say that, if lunar rocks had initial hydrogen contents anywhere close to those of terrestrial rocks, then the fractionation of chlorine into so many different isotopes would never have happened on the Moon. Because of this Sharp and his colleagues say their results suggest a very dry interior of the Moon.
Sharp proposes that Saal and McCubbin’s calculations of high hydrogen contents in some lunar samples are not typical, and perhaps those samples are the product of certain igneous processes that resulted in their “extremely volatile enrichment.” They do not, however, represent the high and variable isotopic chlorine values reported in the majority of lunar rocks, Sharp said.
Still, there could be a compromise between the varied findings. “There are uncertainties that one has to take into account when doing this type of study, ” Sharp told Universe Today, “and if we take the low estimates of Saal and McCubbin’s papers, they are not so different from our findings.”
But the discrepancies, however small, show that perhaps we can’t make generalizations about the entire Moon from limited samples.
“We have not yet looked for water in a wide range of lunar samples,” said Jeff Taylor from the University of Hawaii, who was not involved in any of the aforementioned studies. “It is quite possible that the initial differentiation of the Moon and subsequent processes such as mantle overturn concentrated whatever water the Moon had into certain areas. Until we measure more samples, including samples from the farside (represented by many of the lunar meteorites and eventually by sample-return missions), we will not know for sure how much water is in the bulk Moon.”
In combination, all the recent studies of the lunar surface show there is likely a complex chemistry on the Moon that we have yet to understand.
“In other words,” said Taylor, “we need more work!”
High-resolution view from LRO of an unusual crater near Moon’s north pole, Rozhdestvensky (110 miles, or 177 kilometers in diameter). Credit: NASA
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Radar has been used since the 1960s to map the lunar surface, but until recently it has been difficult to get a good look at the Moon’s poles. In 2009, the Mini-SAR radar instrument on the Chandrayaan-1 spacecraft was able to map more than 95% of both poles at 150 meter radar resolution, and now the Mini-RF instrument on the Lunar Reconnaissance Orbiter — which has 10 times the resolution of the Mini-SAR — is about halfway through its first high-resolution mapping campaign of the poles. The two instruments are revealing there are likely massive amounts of water in the permanently shadowed craters at the poles, with over 600 million metric tons at the north pole alone. “If that was turned into rocket fuel, it would be enough to launch the equivalent of one Space Shuttle per day for over 2,000 years,” said Paul Spudis, principal investigator for the Mini-SAR, speaking at the annual Lunar Forum at the Ames Research Center in July.
Both Spudis and Ben Bussey, principal investigator for LRO’s Mini-RF shared images from their respective instruments at the Forum, highlighting polar craters that exhibit unusual radar properties consistent with the presence of ice.
They have found over 40 craters on the Moon’s north pole that exhibit these properties.
Both instruments provide details of the interior of shadowed craters, not able to be seen in visible light. In particular, a measurement called the circular polarization ratio (CPR) shows the characteristics of the radar echoes, which give clues to the nature of the surface materials in dark areas. The instruments send pulses of left-polarized radio waves to measure the surface roughness of the Moon. While smooth surfaces send back a reversed, right-polarized wave, rough areas return left-polarized waves. Ice, which is transparent to radio waves, also sends back left-polarized waves. The instruments measure the ratio of left to right circular polarized power sent back, which is the CPR.
Few places – even in our solar system — have a CPR greater than 1 but such places have thick deposits of ice, such as Martian polar caps, or the icy Galilean satellites. They are also seen in rough, rocky ejecta around fresh, young craters, but there, scientists also observe high CPR outside the crater rim such as in this image, below of the Main L crater on the Moon.
The fresh impact crater Main L (14 km diameter), which shows high CPR inside and outside its rim. The histograms at right show that the high CPR values within (red line) and outside the crater rim (green line) are nearly identical. Credit: NASA
Most of the Moon has low CPR, but dozens of anomalous north pole craters, such as a small 8 km crater within the larger Rozhdestvensky crater, had a high CPR on the inside, with a low CPR on the rims. That suggests some material within the craters, rather than surface roughness, caused the high CPR signal.
“Geologically, we don’t expect rough, fresh surfaces to be present inside a crater rim but absent outside of it,” Spudis said. “This confirms the high CPR in these anomalous craters is not caused by surface roughness, and we interpret this to mean that water ice is present in these craters.” An “anomalous” crater on the floor of Rozhdestvensky, near the north pole of the Moon. The histogram of CPR values clearly shows that interior points (red line) have higher CPR values than those outside the crater rim (green line). Credit: NASA
Additionally, the ice would have to be several meters thick to give this signature. “To see this elevated CPR effect, the ice must have a thickness on the order of tens of wavelengths of the radar used,” he said. “Our radar wavelength is 12.6 cm, therefore we think that the ice must be at least two meters thick and relatively pure.”
Recent Mini-SAR images (top image) from LRO confirm the Chandrayaan-1 data, with even better resolution. The Mini-RF, Bussey said, is equivalent to a combination of the Arecibo Observatory and the Greenbank Radio telescope in looking at the Moon. “Our polar campaign will map from 70 degrees to the poles and so far we are very pleased with the coverage and quality of the data,” Bussey said.
Spudis said they are seeing less anamolous craters on the Moon’s south pole, but both he and Bussey are looking forward to comparing more data between the two radar instruments to learn more about the permanently shadowed craters on the Moon.
Additionally, other instruments on LRO will also provide insights into the makeup of these anomalous craters.
This schematic shows the daytime cycle of hydration, loss and rehydration on the lunar surface. Credit: University of Maryland/McREL.
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“Water cycle on the Moon” is a phrase that many people – including lunar scientists – were never expecting to hear. This surprising new finding of ubiquitous water on the surface of the Moon, revealed and confirmed by three different spacecraft last year, has been one of the main topics of recent discussion and study by lunar researchers. But figuring out the cycle of how water appears and disappears over the lunar day remains elusive. As of now, scientists suspect a few different processes that could be delivering water and hydroxyl (OH) to the lunar surface: meteorites or comets hitting the Moon, outgassing from the Moon’s interior, or the solar wind interacting with the lunar regolith. But so far, none of the details of any of these processes are adding up.
Dana Hurley from The Johns Hopkins University Applied Physics Laboratory is part of team of scientists attempting to model the lunar water cycle, and she discussed the work at the NASA Lunar Science Institute’s third annual Lunar Forum at Ames Research Center, July 20-22, 2010.
“When we do the model, we assume the way that the water is lost is through photodissociation, and so that sets the timescale,” Hurley told Universe Today. “And using that timescale the amount that is coming in through the solar wind or micrometeorites can’t add up to the amount observed if it is in steady state, so something is not jiving.”
Photodissociation involves the breaking up of a substance into simpler components by the radiant energy of sunlight.
It appears the amount of water varies over the course of the lunar day. Two observations a week apart by a spectrometer on the repurposed Deep Impact spacecraft (now called EPOXI) showed the region that was near the Moon’s terminator at dawn had a detectable amount of water and hydroxyl, and a week later when it was near noon, those substances were gone. But the new region at dawn then had H2O and OH.
One theory holds that the water and hydroxyl are, in part, formed from hydrogen ions in the solar wind. By local noon, when the moon is at its warmest, some water and hydroxyl are lost. By evening, the surface cools again, and the water and hydroxyl return.
But, Hurley said, the solar wind in steady state does not reproduce the observed surface density of water and hydroxyl.
Additionally, looking at the other possible sources — the known source rate of micrometeoroids and comets — doesn’t provide the amount of observed H20 and OH either.
“We’d really like to have a lot more observations to understand how it evolves over the course of the day,” Hurley said. Water in Polar Regions on the Moon Credit: ISRO/NASA/JPL-Caltech/Brown Univ./USGS
In her talk, Hurley said her team has been trying to look at all possible angles and ideas, including recent larger comet hits on the Moon, or potentially a seasonal event where water deposited at winter poles could be released when it warms up in summer. But so far none of these ideas have been tested or modeled, and as of now do not provide a solution to the daily cycle of water that was observed.
She also noted that since there are obviously some unique processes going on, the interaction between the surface and atmosphere needs more study.
“The surface and atmosphere are coupled,” Hurley said in an interview with Universe Today. “The atmosphere is produced from the surface; there is no atmosphere that lasts for a long time on the Moon and it is constantly being produced and lost. And so it is coming from the surface, either from something that is coming from the lunar regolith grains or something that is interacting with those grains, whether it is solar wind or something that is impacting. So, the surface is the source of the atmosphere and that atmosphere comes back and interacts with the surface again. And you really have to understand that whole system.”
So, what is her best guess as to the source of the water?
Hurley said there has to be some sort of recycling going on within the regolith, and perhaps a complex surface chemistry that allows the H20 and OH to exist for longer periods of time, which would better explain the surface density.
“What I’ve looked at is what could be happening in the atmosphere and how things hop around from the surface up and then back down to the surface,” she said. “The lunar regolith is rather loose, and these small particles and gases can go down within the regolith and be within the top several centimeters and work their way down and back out. So there is an exchange going on in that top layer that is kind of acting as a reservoir. That is my best guess of what is going on.”
If there’s only one thing we’ve learned from all the highly successful recent Moon missions – the Lunar Reconnaissance Orbiter, LCROSS, Chandrayaan-1 and Kaguya — it’s that the Moon is perplexingly different from our perceptions of the past 40 years. The discovery of water and volatiles across the surface and in the permanently shadowed regions at the poles changes so many of the notions we’ve had about Earth’s constant companion. Basically, just within the past year we’ve realized the Moon is not a dry, barren, boring place, but a wetter, richer and more interesting destination than we ever imagined. And so, the proposal for NASA to effectively turn away from any human missions to the Moon, as well as Administrator Charlie Bolden’s ‘been there, done that’ comments is quite perplexing – especially for the lunar scientists who have been making these discoveries.
“It’s been quite a year for the Moon,” said Clive Neal, a lunar geologist from Notre Dame, speaking last week at the NASA Lunar Science Institute’s annual Lunar Forum at Ames Research Center. “And things got quite depressing around February 2010.”
That’s when President Obama proposed a new budget that effectively would end the Constellation program and a return to the Moon.
At the Forum, lunar scientists shared their most recent findings – as well as their attempts to model and comprehend all the data that is not yet understood. But they saved any discussion of NASA’s future until the final presentation of the meeting.
“Hopefully this talk will stop you from running out of here ready to hang yourself or slit your wrists,” quipped Neal, who led the final session.
The week began, however, with keynote speaker Andrew Chaikin – author of the Apollo ‘bible,’ “A Man on the Moon,” and several other space-related books — saying, “We have to erase that horrendous ‘been there done that’ notion.” Chaikin also shared a famous Peanuts cartoon showing Lucy pulling the football out from under from Charlie Brown. No caption was needed for everyone to understand to what Chaikin was referring.
“With all of these new discoveries, we should have ample reason to believe that humans will follow,” said Chaikin. But right now, he added, the man in the Moon looks a little like Rodney Dangerfield. “The Moon wants – and deserves – respect.”
“It appears NASA’s focus might be shifting to Near Earth Objects,” said Neal, “but the Moon is the nearest Near Earth Object. It’s quicker, safer and cheaper to get humans there, and the important thing to recognized that there’s a lot left to explore, and a lot to do on the Moon.”
Only 5% of the Moon’s surface has been explored by humans, and Neal showed scaled maps of the Apollo landing sites overlaid on maps of Africa, Europe and the US, revealing just how small a portion of the Moon has been explored directly by humans. The map below shows the Apollo 11 crew’s movement on the Moon can fit within the size of a soccer (football) field.
Apollo 11 VS. a soccer (football) field. Credit: NASA History website. Click for larger version.
Additionally, the latest data reveal that the Apollo sites were in no way representative of the entire Moon.
In light of the proposed plan to give up on the Moon, Neal said there probably is a lot of misperceptions by the American public, as well as in other countries that there’s nothing to do or learn at the Moon. But he believes nothing could be further from the truth.
“What we’ve heard over the last couple of days are fantastic talks and seen wonderful posters in regard to the vibrancy of lunar exploration and science, and seen that exploration enables science and that science enables exploration. The Moon is a Rosetta Stone for solar system exploration and science. The recognition of a possible lunar magma ocean has resulted in terrestrial and Martian magma oceans being proposed. This could be the way terrestrial planets evolve and the Moon is begging us to go back and explore to figure that out.”
There’s also the studies of preserved impacts on the lunar surface which represents a look back in time where we can figure out how to do date planetary surfaces, test cataclysm hypotheses, and study how airless bodies undergo space weathering, which has a direct application to NEO research. Studying cold trap deposits has direct applicability to learning more about the planet Mercury, and lunar regolith contains information about the history of our Sun.
There are proposals for doing radio astronomy from the lunar farside, which will probe the dark ages of the Universe and look back to when the first stars turned on. “So the Moon is a gateway to the Universe,” Neal said. “You can do so much more with the moon — its not just the moon, it’s the solar system and beyond.”
In addition there are many unresolved scientific questions about the Moon. What are the locations and origins of shallow Moon quakes, and large lunar seismic events? How does the lunar regolith affect transmission of seismic energy? What is the nature of the lunar volatiles in the permanently shadowed regions at the lunar poles? What is the mechanism for the adsorption of water, hydroxyl and other minerals recently found on the Moon’s surface? What is nature of lunar core?
When Constellation was proposed, returning to the Moon was said to be a testbed for going on to Mars. It would be a safe and more economical way to test out systems and technology needed for going to the Red Planet. So, what has changed?
Primarily the budget. There weren’t enough funds in Constellation’s coffers to go to the Moon and then Mars. It primarily became a Moon-only program, which many said, didn’t bring us to the “real” destination that everyone really wants: Mars.
And money is still the real issue for not returning to the Moon in the new proposals of going to NEO’s and then Mars. If money weren’t an object, we’d do it all.
But the Moon offers a great local to test out human missions to Mars. “The Moon offers one-sixth of Earth’s gravity,” Neal said,” and we do not know what happens to the human body over time in that gravity, and we can only extrapolate what happens there and on Mars’ one-third gravity. We could test out life support, the growth of crops, the radiation environment and more. The ‘feed forward’ there is quite important where you can simulate a Mars mission on Moon. To develop and test your radiation shielding in the real environment on the Moon is more of a test than flying on the space station.”
Both Neal and Chaikin said they could go on and on about the benefits of returning to the Moon, and they also book-ended the Lunar Forum by saying it is up to the lunar scientists and Moon enthusiasts to educate the public, other scientists and even NASA about the importance of the Moon.
“We have to do a better job of educating the public – even dealing with the conspiracy theorists,” Neal said. “We need to get into schools and educate about what NASA has done, and what they are doing now. We all take responsibility for that.”
“The Moon is not going to get the respect it deserves unless people are out there talking about it,” said Chaikin.
A. Light microscopy image of 72255,89. (B) Higher magnification image of transition from light to dark material in area shown in (A). (C) Raman spectra of three types of graphite analyzed in the sample. Credit: A. Steele, et al.
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Long-held secrets continue to be unlocked from the Moon. Researchers taking a new look at a rock brought back by the Apollo 17 mission have discovered graphite in the form of tiny whiskers within the lunar sample. Just like the recent finding of water on the Moon, it was previously thought that any carbon present in the Apollo rocks came from terrestrial contamination from the way the lunar samples were collected, processed or stored. Andrew Steele, who led a team from the Carnegie Institution’s Geophysical Laboratory said the graphite could have come from carbonaceous impactors that struck both the Moon and Earth during the Late Heavy Bombardment, approximately 4.1 to 3.8 billion years ago, and if so, could provide a new and important source of information about this period in the solar system’s early history.
“We were really surprised at the discovery of graphite and graphite whiskers,” Steele said. “We were not expecting to see anything like this.”
The tiny graphite whiskers or needles were found in multiple spots within a specific area of lunar sample 722255 from the Mare Serenitatis impact crater in the Taurus-Littrow region, indicating that the minerals are in fact from the Moon and not just contamination.
Steele told Universe Today that he and his team don’t think the graphite originated on the Moon, but haven’t ruled it out completely.
“Our initial thought is that it is from the impactor, as we find it in a very fine grained impact melt breccias,” he said in an email. “I am currently looking in more pristine lunar rocks, i.e. lavas that do not contain evidence of meteorite material, for carbon phases.”
He added that the graphite may have come from the impactor itself, or it may have formed from the condensation of carbon-rich gas released during the impact.
The team used Raman imaging spectroscopy (CRIS) on a thin section of a freshly fractured surface of the rock. This identifies minerals and carbon species and their spatial relationship to each other beneath the surface of a sample. Steele said even though this rock has been on Earth since 1972, new techniques and instruments allowed for the new discovery.
“The analytical spot size is smaller and so we can look at smaller phases,” he said. “The sensitivity is better in the newer instruments and we can use spatially resolved methods that are much more sensitive than in the Apollo era.”
Impact breccias are made up of a jumble of smaller fragments that formed when the moon was struck by an asteroid or other object.
Other previous spectroscopy of the Moon’s surface has also found trace amounts of carbon, but it was thought to have come from the solar wind. However, Steele said he and his team have also ruled that out as the source.
“Several lines of reasoning confirm that the observed graphite and graphite whiskers (GW) are indigenous to the sample,” said the team in their paper. “In particular, all known GW synthesis methods involve deposition from a carbon-containing gas at relatively high temperatures ranging from 1273 to ~3900 K. Thus, the GWs identified in 72255 cannot have been synthesized as a result of sample handling and preparation. Moreover, they could not have been implanted by solar wind, because this carbon is typically too small to identify structurally at the magnifications used. The crystalline graphite grains detected here are likely either intact remnants of graphite and GWs from the Serentatis impactor, or they could have formed from condensation of carbon-rich gas released during impact.”
Steele said their findings indicate that impacts may be another process by which GWs can form in our solar system. Additionally, it appears carbonaceous material from impacts at the time of the Late Heavy Bombardment (LHB), and at a time when life may have been emerging on Earth, does survive on the Moon.
“The Solar System was chaotic with countless colliding objects 3.8 billion years ago,” Steele said in a press release. “Volatiles—compounds like water and elements like carbon were vaporized under that heat and shock. These materials were critical to the creation of life on Earth.”
While the impacts to Earth during that period have since been erased, craters on the Moon are still pristine, so the Moon potentially holds a record of the meteoritic carbon input to the Earth-Moon system, when life was just beginning to emerge on Earth.
The research is published in the July 2, 2010, issue of Science.
One year ago today, the Lunar Reconnaissance Orbiter (LRO) officially reached orbit about the Moon, and in the past 12 months has gathered more digital information than any previous planetary mission in history. NASA says that maps and datasets collected by LRO’s state-of-the-art instruments will form the foundation for all future lunar exploration plans, as well as be critical to scientists working to better understand the moon and its environment. To celebrate one year in orbit, here are ten great observations made by LRO.
LRO's Diviner instrument found the coldest place in the solar system. Credit: NASA/Goddard/University of California, Los Angeles
1. Coldest Place in the Solar System.
If you think Pluto, a KBO, or the farthest reaches of our solar system are cold, a location closer to Earth is actually colder. Diviner, LRO’s temperature instrument, found a place in the floor of the moon’s Hermite Crater that was detected to be -415 degrees Fahrenheit (-248 Celsius) making it the coldest temperature measured anywhere in the solar system. For comparison, scientists believe that Pluto’s surface only gets down to about -300 degrees Fahrenheit (-184 Celsius). Extremely cold regions similar to the one in Hermite Crater were found at the bottoms of several permanently shaded craters at the lunar south pole and were measured in the depths of winter night.
Enlargement of area surrounding Apollo 11 landing site. Credit: NASA/GSFC/Arizona State University
2. Where Humans Have Walked on the Moon
LRO’s views of the Apollo landing sites are nothing short of stunning, not to mention exciting. Above is LRO’s latest looks at the Apollo 11 landing site, which clearly shows where the descent stage (about 12 feet in diameter) was left behind as well as the astronauts’ tracks and the various equipment they deployed. This LRO data has important scientific value, as it provides context for the returned Apollo samples. Beyond their use for science, the images of all six manned landing sites observed by LRO provide a reminder of NASA’s proud legacy of exploration and a note of inspiration about what humans are capable of in the future.
A pit on the Moon. Credit: NASA/Goddard/Arizona State University
3. Caves on the Moon
What could be more exciting than finding a cave on the Moon, a potential future lunar habitat for human explorers? LRO has now collected the most detailed images yet of at least two lunar pits, quite literally giant holes in the moon. Scientists believe these holes are actually skylights that form when the ceiling of a subterranean lava tube collapses, possibly due to a meteorite impact punching its way through. One of these skylights, the Marius Hills pit, was observed multiple times by the Japanese SELENE/Kaguya research team. With a diameter of about 213 feet (65 meters) and an estimated depth of 260 to 290 feet (80 to 88 meters) it’s a pit big enough to fit the White House completely inside. The image featured here is the Mare Ingenii pit. This hole is almost twice the size of the one in the Marius Hills and most surprisingly is found in an area with relatively few volcanic features.
The Russian Lunokhod rover was imaged by LRO. Credit: NASA/Goddard/Arizona State University
4. Finding Missing Spacecraft
Lunokhod 1 was the name of a Russian robotic rover that landed on the moon in 1970 and navigated about 6 miles (10 km) of the lunar surface over 10 months before it lost contact in September 1971. Scientists were unsure of the rover’s whereabouts, though at least one team of researchers were searching for it, hoping to bounce a laser off of its retroreflector mirrors. This past March however, the LROC team announced they had spotted it, miles from the location the laser team had been searching. Using the info provided by LRO, a laser pulse was sent to Lunokhod 1 and contact was made with the rover for the first time in nearly four decades. Not only did Lunokhod 1’s retroreflector return a signal, but it returned one that was about five times better than those that have routinely been returned by Lunokhod 2’s mirrors over the years.
The Apollo 14 crew came close to seeing the rim of Cone Crater, but not quite. Credit: NASA/Goddard/Arizona State University
5. Apollo 14’s Near Miss of Seeing Cone Crater.
When the Apollo 14 crew of Alan Shepard and Edgar Mitchell walked across their landing site at Fra Maura, they hoped to be able to gather samples from the rim of Cone Crater. But they didn’t ever find the rim, and without a roadmap or guideposts along the way to help them find it, (and also they didn’t have the benefit of riding on the lunar rover so had to walk the entire time). They walked nearly a mile (1400 meters) and the steep incline of the crater rim made the climb difficult, raising the astronaut’s heart rates. Plus the tight schedule of the activity resulted in mission control ordering them to gather whatever samples they could and return to the landing module. They never reached the edge of the crater. Though geologists say it did not greatly affect the success of the scientific goal, the astronauts were personally disappointed in failing to make it to the top. Images from LRO now show precisely just how far the astronauts traveled and how close they came to reaching the crater, their tracks ending only about 100 feet (30 meters) from the rim!
The rim of Cabeus Crater. Credit: NASA/Goddard/Arizona State University
6. Mountains on the Moon.
On the Earth, we are taught that mountains form over millions of years, the result of gradual shifting and colliding plates. On the moon however, the situation is quite different. Even the largest lunar mountains were formed in minutes or less as asteroids and comets slammed into the surface at tremendous velocities, displacing and uplifting enough crust to create peaks that easily rival those found on Earth. On a few occasions in the past year, NASA has tilted the angle of LRO to do calibrations and other tests. In such cases the camera has the opportunity to gather oblique images of the lunar surface like the one featured here of Cabeus Crater providing a dramatic view of the moon’s mountainous terrain. Cabeus Crater is located near the lunar south pole and contains the site of the LCROSS mission’s impact. Early measurements by several instruments on LRO were used to guide the decision to send LCROSS to Cabeus. During the LCROSS impact LRO was carefully positioned to observe both the gas cloud generated in the impact, as well as the heating at the impact site.
Lunar rilles. Image Credit: NASA/JHUAPL/LSI
7. Lunar Rilles: Mysterious Channels on the Moon
Rilles are long, narrow depressions on the lunar surface that look like river channels. Some are straight, some curve, and others, like the ones highlighted here, are called “sinuous” rilles and have strong meanders that twist and turn across the moon. Rilles are especially visible in radar imagery, like that gathered by LRO’s Mini-RF instrument. The formation of lunar rilles is not well understood. It is believed there may be many different formation mechanisms including ancient magma flows and the collapse of subterranean lava tubes. Imagery from LRO will help researchers to better understand these mysterious “river-like” lunar features.
Areas of constant sunlight on the Moon's south pole. Image Credit: NASA/Goddard
8. Areas of Near Constant Sunlight at the South Pole
One of the most vital resources LRO is searching for on the moon is solar illumination. Light from the sun provides both warmth and a source of energy, two critical constraints to exploration efforts. The moon’s axis is only slightly tilted so there are areas in high elevations at its poles that remain almost constantly exposed to the sun. Using LRO’s precise measurements of topography scientists have been able to map illumination in detail, finding some areas with up to 96% solar visibility. Such sites would have continuous sun for approximately 243 days a year and never have a period of total darkness for more than 24 hours.
With Moon Zoo, you can count craters and boulders on the Moon to help lunar scientists. Credit: NASA/Goddard/Arizona State University
9. Moon Zoo lets you Help Lunar Scientists.
The latest Citizen Science project from the Zooniverse, Moon Zoo uses about 70,000 high resolution images gathered by LRO, and in these images are details as small as 50 centimeters (20 inches) across. ‘Zooites’ are asked to categorize craters, boulders and more, including lava channels and later, comparing recent LRO images to ones taken years ago by other orbiting spacecraft.
The first tasks are counting craters and boulders. By comparing and analyzing these feature counts across different regions as well as other places like the Earth and Mars, Zooites can help scientists gain a better understanding of our solar system’s natural history.
The Moon's far side -- the part we never see from Earth. Credit: NASA/Goddard
10. Getting a Good Look at the Far Side.
Tidal forces between the moon and the Earth have slowed the Moon’s rotation so that one side of the moon always faces toward our planet. Though sometimes improperly referred to as the “dark side of the moon,” it should correctly be referred to as the “far side of the moon” since it receives just as much sunlight as the side that faces us. The dark side of the moon should refer to whatever hemisphere isn’t lit at a given time. Though several spacecraft have imaged the far side of the moon since then, LRO is providing new details about the entire half of the moon that is obscured from Earth. The lunar far side is rougher and has many more craters than the near side, so quite a few of the most fascinating lunar features are located there, including one of the largest known impact craters in the solar system, the South Pole-Aitken Basin. The image highlighted here shows the moon’s topography from LRO’s LOLA instruments with the highest elevations up above 20,000 feet in red and the lowest areas down below -20,000 feet in blue.
This pit in Mare Ingenii, the "sea of cleverness," is about 130 meters (427 feet) in diameter! Image width is 550 meters (1,805 feet), illumination is from the upper right, LROC Frame: NAC M128202846LE. Credit: NASA/Goddard/Arizona State University
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Is this a window into the interior of the Moon, and an entrance to a potential future lunar habitat? The Lunar Reconnaissance Orbiter Camera has taken a closer look at what is thought to be a skylight into a lava tube in the Mare Ingenii (The Sea of Cleverness) region, one of the few lunar mare features on the far side of the Moon. This skylight is huge — about 130 meters (427 feet) in diameter — and is probably the result of a partially collapsed lava tube. But lunar geologists really weren’t expecting to see this kind unusual feature in this region. Previously, a skylight, or open pit was found in the Marius Hills region in the Ocean of Storms on the near side which is filled with volcanic domes and rilles where a lava tube might form. However, those kinds of volcanic features are not found in Mare Ingenii. LRO will definitely be taking additional looks at this pit.
The Japanese SELENE/Kaguya spacecraft first discovered this irregularly-shaped hole, visible in the top image at LROC’s 0.55 m/pixel resolution. The boulders and debris resting on the floor of the pit are partially illuminated (left side of the pit) and probably originated at the surface, falling through the pit opening during collapse.
Arrow indicates location of pit. "S" indicates one of the numerous lunar swirls located in this region. Image is a portion of LROC WAC mosaic, 200 meters per pixel resolution; image width is 160 km (100 miles). Credit: NASA/Goddard/Arizona State University
This could be an important find for several reasons. Lava tubes are important in understanding how lava was transported on the early moon, but they could also provide a home to future human explorers. This one on the far side would be a great place to set up a base for future telescopes proposed for observations out into the Universe from the Moon’s far side. The Moon’s surface is a harsh place, the human body doesn’t do well when exposed to the constant radiation present on the Moon’s atmosphere-less environment. Long term human presence would work if astronauts could spend most of their time shielded underground. While excavating a hole large enough to fit an entire moon colony in it would be a huge engineering challenge, these lava tubes could provide ready-made locations for a well-shielded base.
Here’s a look at a huge lava tube in Hawaii. It looks almost man-made, but is a natural feature created by volcanism:
Thurston lava tube is located on Kilauea in Hawaii. Credit: P. Mouginis-Mark, LPI
How lava tubes form: when lava flows out onto the surface, it cools on top and may form a solid roof. The roof insulates the still-liquid lava below it, allowing it to continue to flow, sometimes for several kilometers. At the end of the eruption, the lava can drain completely out of the tube, leaving a hollow remnant of the flow that forms an underground cavern. This tube, called Thurston Tube, is about 3 meters in height.
Moon rocks from the Apollo 11 mission. Credit: NASA
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A new look at Moon rocks from the Apollo missions, along with a lunar meteorite show a much higher water content in the Moon’s interior than previously thought. Using secondary ion mass spectrometry (SIMS) which can detect elements in the parts per million range, scientists at the Carnegie Institution’s Geophysical Laboratory found the minimum water content ranged from 64 parts per billion to 5 parts per million—at least two orders of magnitude greater than previous results. The science team says their research suggests that the water was preserved from the hot magma that was present when the Moon began to form some 4.5 billion years ago. “The concentrations are very low and, accordingly, they have been until recently nearly impossible to detect,” said team member Bradley Jolliff of Washington University in St. Louis. “We can now finally begin to consider the implications—and the origin—of water in the interior of the Moon.”
The prevailing belief is that the Moon came from a giant-impact event, when a Mars-sized object hit the Earth and the ejected material coalesced into the Moon. In this new study of lunar samples, scientists determined that water was likely present very early in the formation history as the hot magma started to cool and crystallize. This result means that water is native to the Moon.
The SIMS technique measures hydroxyl by bombarding the grains of a type of phosphorous, water-bearing mineral called apatite with high-energy particles and counting the ions that are ejected. Based on the SIMS measurements, the scientists authors place the lower limit for the total lunar water at 100 times greater than previous estimates, and speculate that water may be “ubiquitous” in the moon’s interior.
The study could alter current theories about lunar magmatism (how igneous rock formed from magma), and how the moon formed and evolved.
Water is showing up in all sorts of unexpected places on the Moon. In September of 2009, a trio of spacecraft detected a ubiquitous layer of a combination of water (H2O) and hydroxyl (OH) that resides in upper millimeter of the lunar surface. It doesn’t actually amount to much; only about two tablespoons of water is believed to be present in every 1,000 pounds (450 kg). Then in October of 2009, the LCROSS impactor and spacecraft detected “buckets” of water in the permanently shadowed region of Cabeus crater near the moon’s south pole.
In 2008 water was found inside volcanic glass beads in Apollo Moon rocks, which represent solidified magma from the early moon’s interior. That finding led to this new study, using the SIMS. The scientists combined the measurements taken with the spectrometer with models that characterize how the lunar magma crystallized as the Moon cooled. They then inferred the amount of water in the apatite’s source magma, which allowed them to extrapolate the result to estimate the total amount of water that is present on the moon.
“For over 40 years we thought the Moon was dry,” said lead author of the new study, Francis McCubbin.
