NASA LRO: Gravity anomalies bordering the Moon's Procellarum region

The Lunar Orbiter Laser Altimeter (LOLA), aboard NASA's Lunar Reconnaissance Orbiter (LRO), collected data to produce this image showing the topography of Earth’s moon. 

Gravity anomalies bordering the Procellarum region appear superimposed in blue. 

The image depicts border structures using gravity gradients calculated with information obtained by NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission. 

Researchers interpret these gravity anomalies as ancient lava-flooded rift zones buried beneath the volcanic plains (or maria) on the nearside of the moon.

Credit: NASA

More Information
"Structure and evolution of the lunar Procellarum region as revealed by GRAIL gravity data"
Jeffrey C. Andrews-Hanna, Jonathan Besserer James W. Head III, Carly J. A. Howett, Walter S. Kiefer, Paul J. Lucey, Patrick J. McGovern, H. Jay Melosh, Gregory A. Neumann, Roger J. Phillips, Paul M. Schenk, David E. Smith, Sean C. Solomon & Maria T. Zuber - Nature 514, 68–71 (02 October 2014) doi:10.1038/nature13697 - Published online 01 October 2014

NASA GRAIL: Procellarum region on the Moon

The Moon, as observed in; GRAIL gravity gradients (top), topography (center, where red is high and blue is low), and in visible light (bottom). 

The Procellarum region is a broad region of low topography covered in dark mare basalt. 

The GRAIL gravity gradients reveal a giant rectangular pattern of structures surrounding the region. 

Credit: NASA /Colorado School of Mines /MIT /JPL /Goddard Space Flight Center

New data obtained by NASA's GRAIL mission reveals that the Procellarum region on the near side of the moon, a giant basin often referred to as the "man in the moon," likely arose not from a massive asteroid strike, but from a large plume of magma deep within the moon's interior.

The Procellarum region is a roughly circular, volcanic terrain some 1,800 miles in diameter, nearly as wide as the United States.

One hypothesis suggested that it was formed by a massive impact, in which case it would have been the largest impact basin on the moon.

Subsequent asteroid collisions overprinted the region with smaller, although still large, basins.

Now researchers from MIT, the Colorado School of Mines, and other institutions have created a high-resolution map of the Procellarum region, and found that its border is not circular, but polygonal, composed of sharp angles that could not have been created by a massive asteroid.

Instead, researchers believe that the angular outline was produced by giant tension cracks in the moon's crust as it cooled around an upwelling plume of hot material from the deep interior.

Maria Zuber, the E.A. Griswold Professor of Geophysics and also MIT's vice president for research, says that as cracks occurred, they formed a "plumbing system" in the moon's crust through which magma could meander to the surface.

Magma eventually filled the region's smaller basins, creating what we see today as dark spots on the near side of the moon, features that have inspired the popular notion of a "man in the moon."

"A lot of things in science are really complicated, but I've always loved to answer simple questions," says Zuber, who is principal investigator for the GRAIL (Gravity Recovery and Interior Laboratory) mission.

"How many people have looked up at the moon and wondered what produced the pattern we see, let me tell you, I've wanted to solve that one!"

Team solves the origin of the Moon's 'mascons' mystery

Free-air gravitational acceleration anomalies over the 420-km-diameter Freundlich-Sharonov impact basin on the far side of the Moon. The color scale ranges between -300 and 300 mgal.

The image is 1,000 km wide. 

Credit: H. J. Melosh, Purdue University and the NASA GRAIL team

A mystery of the moon that imperiled astronauts and spacecraft on lunar missions has been solved by a Purdue University-led team of scientists as part of NASA's GRAIL mission.

Large concentrations of mass lurk on the lunar surface hidden like coral reefs beneath the ocean waves - an unseen and devastating hazard.

These concentrations change the gravity field and can either pull a spacecraft in or push it off course, sealing its fate to a crash on the face of the moon.

Jay Melosh

"In 1968 these mass concentrations were an unwelcome discovery as scientists prepared for the Apollo landings, and they have remained a mystery ever since," said Jay Melosh, a member of the Gravity Recovery and Interior Laboratory, or GRAIL, science team who led the research.

"GRAIL has now mapped where they lay, and we have a much better understanding of how they developed. If we return to the moon, we can now navigate with great precision."

A better understanding of these features also adds clues to the moon's origin and evolution and will be useful in studying other planets where mass concentrations also are known to exist including Mars and Mercury, said Melosh, who is a distinguished professor of earth, atmospheric and planetary sciences and physics.

"We now know the ancient moon must have been much hotter than it is now and the crust thinner than we thought," he said.

"For the first time we can figure out what size asteroids hit the moon by looking at the basins left behind and the gravity signature of the areas. We now have tools to figure out more about the heavy asteroid bombardment and what the ancient Earth may have faced."

The team confirmed the standing theory that the concentrations of mass were caused by massive asteroid impacts billions of years ago and determined how these impacts changed the density of material on the moon's surface and, in turn, its gravity field.

A paper detailing the results will be published online by the journal Science on Thursday (May 30).

In addition to Melosh, Purdue team members include Andrew Freed, associate professor of earth, atmospheric and planetary sciences, and graduate students Brandon Johnson and David Blair.

Additional team members include Maria Zuber, GRAIL principal investigator and professor at the Massachusetts Institute of Technology; J. Andrews-Hanna of the Colorado School of Mines; S. Solomon of Columbia University; and the GRAIL Science Team.

"The explanation of mascons has eluded scientists for decades," Zuber said. "Since their initial discovery they have also been observed on Mars and Mercury, and by understanding their formation on the moon we have greatly advanced knowledge of how major impacts modified planetary crusts."

The mass concentrations form a target pattern with a gravity surplus at the bulls-eye surrounded by a ring of gravity deficit and an outer ring of gravity surplus.

The team found that this pattern arises as a natural consequence of crater excavation, collapse and cooling following an impact.

The team determined that the increase in density and gravitational pull at the bulls-eye was caused by lunar material melted from the heat of the asteroid impact.

The melting causes the material to become more concentrated, stronger and denser, and pulls in additional material from the surrounding areas, Melosh said.

The large asteroid impacts also caused big holes into which the surrounding lunar material collapsed.

As the cool, strong lunar crust slid into the holes it bent downward, forming a rigid, curved edge that held down the material beneath it and prevented it from fully rebounding to its original surface height.

This causes a ring with less gravitational pull because the mass is held farther below the surface, the top of which is what most influences the gravitational signature, he said.

More information: "The Origin of Lunar Mascon Basins," by H.J. Melosh et al. Science, 2013.

NASA GRAIL Mission: LRO's LAMP Captures Lunar Impact

These models show the time evolution for hydrogen (left) and mercury (right) as plumes of gas rapidly expand into the vacuum of space following the planned impact of the GRAIL twins onto the lunar surface. 

Data from the Lyman-Alpha Mapping Project (LAMP) aboard NASA’s Lunar Reconnaissance Orbiter accurately constrain such models used to understand the impact event. 

Credit: JHUAPL/SwRI/NASA

When NASA's twin GRAIL spacecraft made their final descent for impact onto the Moon's surface last December, the Lunar Reconnaissance Orbiter's sophisticated payload was in position to observe the effects.

As plumes of gas rose from the impacts, the Lyman Alpha Mapping Project (LAMP) aboard LRO detected the presence of mercury and hydrogen and measured their time evolution as the gas rapidly expanded into the vacuum of space at near-escape velocities.

NASA intentionally crashed the GRAIL twins onto the Moon on Dec. 17, 2012, following successful prime and extended science missions.

Both spacecraft hit a mountain near the lunar north pole, which was shrouded in shadow at the time.

Developed by Southwest Research Institute (SwRI), LAMP uses a novel method to peer into the darkness of the Moon's permanently shadowed regions, making it ideal for observations of the Moon's night-side and its tenuous atmospheric constituents.

Dr. Kurt Retherford

"While our results are still very new, our thinking is that the hydrogen detected from the GRAIL site might be related to an enhancement at the poles caused by hydrogen species migrating toward the colder polar regions," says Dr. Kurt Retherford, LAMP principal investigator and a principal scientist at SwRI.

"Combining GRAIL results with LCROSS results could tell us more about hydrogen and water near the poles," says Dr. Thomas Greathouse, a LAMP team member and SwRI senior research scientist.

“We have begun to understand that the amount of water ice near the polar regions is higher than was previously thought, but we don't fully understand how it gets there."

LAMP usually observes the night-side lunar surface using light from nearby space (and stars), which bathes all bodies in space in a soft glow.

This Lyman-alpha glow is invisible to human eyes but visible to LAMP as it reflects off the Moon.

However, the new detection of Lyman-alpha emissions from native lunar atomic hydrogen gas released by the impact is a first for LAMP, and for any previous instrument.

NASA Grail Twin Probes Final Flight Path

The NASA GRAIL twin probes' final flight path into their crash site, imaged with data from NASA's Lunar Reconnaissance Orbiter (LRO). 

Credit: NASA/JPL-Caltech/GSFC/ASU

Two space probes that successfully mapped variations in the Moon's gravity field have been deliberately crashed into the lunar surface in a dramatic end to their mission.

They are just the latest in a string of probes to leave their shattered remains on the Moon. The impacts of the GRAIL probes, Ebb and Flow, into a 2.4 km high (1.5 miles) mountain near the lunar north pole, was deliberate and planned in great detail.

NASA decided to destroy the craft in a controlled manoeuvre rather than take the risk, however tiny, that they might later hit one of the historic landing sites of Apollo and unmanned probes.

The two spacecraft, each the size of a washing machine, fired their thrusters one last time to burn up the last of their fuel. They dropped into a lower orbit and hit the peak's southern face, near a crater called Goldschmidt, at 6,050 kph (3,760 mph).

NASA Grail Mission: Twin Probes' Lunar Crash

Two NASA moon probes are slated to slam into the rim of a lunar crater today (Dec. 17), and the space agency will give viewers a behind-the-scenes look at the dramatic action.

The twin Grail spacecraft, known as Ebb and Flow, will crash intentionally near the moon's north pole at 5:28 p.m. EST (2228 GMT) today, bringing their gravity-mapping mission to a spectacular close.

The event will be broadcast on NASA TV and streamed live on the agency's website, beginning at 5 p.m. EST (2200 GMT).

The coverage should last about 35 minutes and will include interviews with Grail team members. The impact site will be in shadow at the time of the crash, so no video of Ebb and Flow's violent demise is expected, NASA officials said.

This graphic highlights locations on the moon NASA considers "lunar heritage sites" and the path NASA's Gravity Recovery and Interior Laboratory spacecraft will take on their final flight. Image released Dec. 13, 2012.

CREDIT: NASA/JPL-Caltech

You can follow along at NASA TV's website www.nasa.gov

NASA Grail: Twin Probes to Crash into Moon Next Week

Artist's concept of NASA's Grail mission. Grail's twin spacecraft are flying in tandem orbits around the moon to measure its gravity field in unprecedented detail. 

CREDIT: NASA/JPL

NASA's twin Grail spacecraft will crash into the lunar surface intentionally next week, bringing their gravity-mapping mission to a spectacular end.

The probes, known as Ebb and Flow, will be commanded to slam into the moon on Dec. 17, NASA officials said.

The agency will host a press conference to discuss the impact and the events leading up to it.

The $496 million Grail mission (Gravity Recovery and Interior Laboratory) launched in September 2011 to map the moon's gravity field in unprecedented detail.

Ebb and Flow arrived in orbit around the moon about one year ago — on New Year's Eve and New Year's Day, respectively.

The washing-machine-size spacecraft were originally tasked with 90-day science missions, which ran from March to May. but NASA extended Grail, allowing the two probes to gather a trove of additional data.

Ebb and Flow have been flying in formation around the moon, detecting the tiny changes in the distance between them caused by lunar mountains, craters and subsurface mass concentrations.

Scientists used these ultra-precise measurements to construct an incredibly accurate map of the lunar gravity field.

This map, unveiled last week at the fall meeting of the American Geophysical Union (AGU) in San Francisco, reveals that the moon's crust is almost completely pulverized.

The surprising find suggests that the moon and other rocky bodies in the inner solar system were pounded by long-ago impacts far more violently than previously believed, researchers said.

The new map was based on data gathered during Grail's original science mission; scientists expect to upgrade it based on measurements the spacecraft made during their extended mission, which brought them even closer to the lunar surface — an average altitude of 14 miles (23 km) as opposed to 34 miles (55 km).

Ebb and Flow are now running low on fuel as expected, NASA officials said, so the end is near for the probes. Mission managers will ensure that they go out in style on Dec. 17.

NASA JPL: GRAIL's Gravity Map of the Moon

This image shows the variations in the lunar gravity field as measured by NASA's Gravity Recovery and Interior Laboratory (GRAIL) during the primary mapping mission from March to May 2012. 

Very precise microwave measurements between two spacecraft, named Ebb and Flow, were used to map gravity with high precision and high spatial resolution. 

The field shown resolves blocks on the surface of about 12 miles (20 kilometers) and measurements are three to five times improved over previous data. Red corresponds to mass excesses and blue corresponds to mass deficiencies. 

The map shows more small-scale detail on the far side of the moon compared to the nearside because the far side has many more small craters.

› See video

Image credit: NASA/JPL-Caltech/MIT/GSFC

Video: GRAIL's Gravity Tour of the Moon - NASA JPL

Embedded video from NASA JPL

This movie shows the variations in the lunar gravity field as measured by NASA's Gravity Recovery and Interior Laboratory (GRAIL) during the primary mapping mission from March to May 2012.

Twin NASA probes orbiting Earth's moon have generated the highest resolution gravity field map of any celestial body.

The new map, created by the Gravity Recovery and Interior Laboratory (GRAIL) mission, is allowing scientists to learn about the moon's internal structure and composition in unprecedented detail.

Data from the two washing machine-sized spacecraft also will provide a better understanding of how Earth and other rocky planets in the solar system formed and evolved.

The gravity field map reveals an abundance of features never before seen in detail, such as tectonic structures, volcanic landforms, basin rings, crater central peaks and numerous simple, bowl-shaped craters.

Data also show the moon's gravity field is unlike that of any terrestrial planet in our solar system.

These are the first scientific results from the prime phase of the mission, and they are published in three papers in the journal Science.

"What this map tells us is that more than any other celestial body we know of, the moon wears its gravity field on its sleeve," said GRAIL Principal Investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge.

"When we see a notable change in the gravity field, we can sync up this change with surface topography features such as craters, rilles or mountains."

According to Zuber, the moon's gravity field preserves the record of impact bombardment that characterized all terrestrial planetary bodies and reveals evidence for fracturing of the interior extending to the deep crust and possibly the mantle. This impact record is preserved, and now precisely measured, on the moon.

The probes revealed the bulk density of the moon's highland crust is substantially lower than generally assumed. This low-bulk crustal density agrees well with data obtained during the final Apollo lunar missions in the early 1970s, indicating that local samples returned by astronauts are indicative of global processes.

"With our new crustal bulk density determination, we find that the average thickness of the moon's crust is between 21 and 27 miles (34 and 43 kilometers), which is about 6 to 12 miles (10 to 20 kilometers) thinner than previously thought," said Mark Wieczorek, GRAIL co-investigator at the Institut de Physique du Globe de Paris.

"With this crustal thickness, the bulk composition of the moon is similar to that of Earth. This supports models where the moon is derived from Earth materials that were ejected during a giant impact event early in solar system history."

The map was created by the spacecraft transmitting radio signals to define precisely the distance between them as they orbit the moon in formation. As they fly over areas of greater and lesser gravity caused by visible features, such as mountains and craters, and masses hidden beneath the lunar surface, the distance between the two spacecraft will change slightly.

Read the full article here: NASA JPL

NASA GRAIL: Lunar twins Ebb and Flow have extended mission to map gravity

NASA’s twin GRAIL spacecraft, named Ebb and Flow, have successfully completed their primary mission of mapping lunar gravity. 

They have now entered an extended mission in order to obtain gravity maps of even higher resolution than before.

The two spacecraft entered this phase of the mission at 16:28 UT on 30 August when they moved to a lower orbit.

The orbital altitude of the extended mission will see the craft at an average of only 23 kilometres (14 miles) above the Moon’s surface, compared to the average orbital height of 55 kilometres (34 miles) during the primary mission.

At this lower altitude Ebb and Flow will be within 8 kilometres (5 miles) of some of the Moon's higher surface features.

The data collected during the primary mission of GRAIL - which stands for Gravity Recovery And Interior Laboratory - is being analysed and "holds the promise of producing a gravity field map of extraordinary quality and resolution" according to Maria Zuber, principal investigator for GRAIL.

"Mapping at a substantially lower altitude during the extended mission, and getting an even more intimate glimpse of our nearest celestial neighbour, provides the unique opportunity to globally map the shallow crust of a planetary body beyond Earth."

The extended mission will run from 30 August until 3 December, and it will map the gravitational fields of small lunar features, such as craters and mountains.

This unprecedented resolution will help scientists to comprehend the formation and evolution of the Moon.

"Ebb and Flow, and our mission operations team, are both doing great, which is certainly notable considering all the milestones and challenges they have experienced," said David Lehman, GRAIL project manager.

"The twins have endured the lunar eclipse of June 4, 2012, and 26 rocket burns since arriving in lunar orbit at the beginning of the year.

Down here in our control room, with all the planning and mission operations we have been doing, it feels as though we've been riding right along with them. Of course, they have the better view."

It was not guaranteed that the GRAIL twins would survive the lunar eclipse in June.

The spacecraft are mainly powered by solar panels, and there were fears that the batteries on board would not be able to power the craft for the duration of the eclipse.

Fortunately, the NASA spacecraft proved their resilience, enabling the extended phase of the mission to go ahead.

Leland Melvin, NASA Associate Administrator for Education, left, Maria Zuber, GRAIL Prinicipal Investigator at the Massachusetts Institute of Technology, and James Green, Director of the Planetary Science Division in the Science Mission Directorate at NASA Headquarters, right, applaud students from Emily Dickinson Elementary School in Bozeman, Mont. during a news conference, Tuesday, Jan. 17, 2012, at NASA Headquarters in Washington. 

Nine hundred classrooms and more than 11,000 students from 45 states, as well as Puerto Rico and the District of Columbia, participated in a contest that began in October 2011 to name the twin lunar probes.

Photo Credit: NASA/Paul E. Alers

 The GRAIL twins map the lunar gravity by measuring the varying distance between two craft using radio signals. The distance between Ebb and Flow will change depending on the amount of mass

below them, allowing the craft a glimpse into the lunar interior.

The GRAIL spacecraft were launched on 10 September 2011, arrived at the Moon over the New Year and began their primary science mission on 7 March 2012.