GRAIL: Gravity Recovery And Interior Laboratory

[Beyond]

...above the moon's Ocean of Storms,... Am i missing something here? Ocean of storms on the moon??

Oceanus Procellarum (Latin for "Ocean of Storms") is a vast lunar mare on the western edge of the near side of Earth's Moon. It is the only one of the lunar maria to be called an "Oceanus" (ocean). This is due to its size; Oceanus Procellarum is the largest of the maria, stretching more than 2,500 km (1,600 mi) across its north-south axis and covering roughly 4,000,000 km² (1,500,000 sq mi). Nevertheless, it is still smaller than the surface area of the Mediterranean Sea on Earth.

Ah..Ok. I don't know Latin.

[bystander]

GRAIL Creates Most Accurate Moon Gravity Map
NASA | JPL-Caltech | GSFC | GRAIL | 2012 Dec 05

Click to play embedded YouTube video.

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.

"We used gradients of the gravity field in order to highlight smaller and narrower structures than could be seen in previous datasets," said Jeff Andrews-Hanna, a GRAIL guest scientist with the Colorado School of Mines in Golden. "This data revealed a population of long, linear gravity anomalies, with lengths of hundreds of kilometers, crisscrossing the surface. These linear gravity anomalies indicate the presence of dikes, or long, thin, vertical bodies of solidified magma in the subsurface. The dikes are among the oldest features on the moon, and understanding them will tell us about its early history."

Image Gallery

Related Videos:

• GRAIL's Map of Moon's Crust
  GRAIL's 'Bouguer' Gravity Moon Map

GRAIL reveals a battered lunar history
Massachusetts Institute of Technology | 2012 Dec 05

Behold! A 'Pounded Moon' Gravity Map
Mike Walls, Space.com | via Discovery News | 2012 Dec 05

Moon’s Inner Crust Almost Completely Pulverized
Universe Today | Nancy Atkinson | 2012 Dec 05

GRAIL First Results Provide Most Precise Lunar Gravity Map Yet
Universe Today | Nancy Atkinson | 2012 Dec 05

http://asterisk.apod.com/viewtopic.php? ... 12#p188945

[neufer]

<<Saturnalia was an ancient Roman festival in honour of the deity Saturn originally held on December 17. The holiday was celebrated with a sacrifice at the Temple of Saturn in the Roman Forum and a public banquet, followed by private gift-giving, continual partying, and a carnival atmosphere that overturned Roman social norms: gambling was permitted, and masters provided table service for their slaves. The poet Catullus called it "the best of days." [Saturnalia was also] a festival of light leading to the winter solstice, with the abundant presence of candles symbolizing the quest for knowledge & truth. The popularity of Saturnalia continued into the 3rd & 4th centuries AD, and as the Roman Empire came under Christian rule, some of its customs may have influenced the seasonal celebrations surrounding Christmas and the New Year.>>

[b][color=#0000FF]GRAIL impact trajectory, with added drama -Ian O'Neill (NOTE: In space, no one can hear a probe scream)[/color][/b]

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How GRAIL will meet its end
By Emily Lakdawalla, 2012/12/13

<<The twin GRAIL spacecraft are nearly out of fuel, and are being directed to a controlled impact near the north pole on the near side of the Moon on December 17. Ending the mission in this way has been planned all along; the news here is the time and location of the planned impact. Here's a preliminary map of the location, an unnamed mountain located at 75.62°N, 26.63°W. (The linked map says "east" but the inset map shows that the numbers are negative and a larger-scale map shows it west of center, so I'm pretty sure it's west, not east.) The end will come on December 17 at 22:28 or 22:29 UTC. Ebb will hit first, followed by Flow about 30 seconds later. >>

[neufer]

GRAIL twins Ebb and Flow to smash into moon today
Astrobob, December 17, 2012

<<At 5:28 p.m. (EST) today Dec. 17, the twin GRAIL (Gravity Recovery and Interior Laboratory) moon probes [Ebb and Flow] will be intentionally crashed into a mountaintop near the moon’s north pole. Now that the paired probes are nearly out of fuel, mission controllers have directed them to the far north of the moon to avoid unintentional crashes near something important like an Apollo landing site.

[Ebb and Flow] discovered the moon’s crust is 21 to 27 miles thick or 6-12 miles thinner than previously thought. It also contains the same amount of aluminum as found in Earth’s crust. Both findings confirm the moon’s origin via the “giant impact hypothesis.” It’s believed the moon formed from materials launched into orbit when Earth was struck by a Mars-sized planet in the chaotic days of planet formation over 4 billion years ago. “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,” said GRAIL co-investigator Mark Wieczorek.

GRAIL discovered a thoroughly fractured and pulverized lunar crust riddled with subsurface “linear gravity anomalies” more than a 100 miles long. These huge cracks deep in the moon’s crust were created by impacts that later filled with lava and solidified into dense pathways of rock. Says Jeff Andrews-Hanna, a GRAIL guest scientist with the Colorado School of Mines: “These linear gravity anomalies indicate the presence of dikes, or long, thin, vertical bodies of solidified magma in the subsurface. The dikes are among the oldest features on the moon, and understanding them will tell us about its early history.”

[b][color=#FF0000][size=125]The impact strikes will happen on a mountain forming part of a crater wall near Anaxagoras crater.[/size] Credit: NASA[/color][/b]

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With the two probes now nearly out of fuel and orbiting only as high above the lunar surface as a jetliner, they’re on a collision course with an unnamed mountain near the crater Anaxagoras. The scene will be hidden in shadow at the time of impact. The first to go will be Ebb at 5:28:40 p.m. (5ST) with Flow following 20 seconds later. Slamming into rock at 3,750 mph, each probe will create a faint flash of light upon impact that might be visible through a telescope. Observers on the East Coast are favored since the flashes will occur when the moon’s in a dark sky. For Duluth, Minn. and around the Midwest the sun will just be setting at that time.>>

[b][color=#FF0000][size=125]Anaxagoras warns the[/size][/color][/b] [url=http://asterisk.apod.com/memberlist.php?mode=viewprofile&u=138689][b][size=125]lunatics[/size][/b][/url] [b][color=#FF0000][size=125]about the Grail crash spot.[/size][/color][/b]

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Anaxagoras (Ancient Greek: Ἀναξαγόρας, Anaxagoras, "lord of the assembly"; c. 500 – 428 BC) was a Pre-Socratic Greek philosopher. Born in Clazomenae in Asia Minor, Anaxagoras was the first philosopher to bring philosophy and the spirit of scientific inquiry from Ionia to Athens. According to Diogenes Laertius and Plutarch he fled to Lampsacus due to a backlash against his pupil Pericles.

Anaxagoras's observations of the celestial bodies and the fall of meteorites led him to form new theories of the universal order. He attempted to give a scientific account of eclipses, meteors, rainbows, and the sun, which he described as a mass of blazing metal, larger than the Peloponnese. He was the first to explain that the moon shines due to reflected light from the sun. He also said that the moon had mountains and believed that it was inhabited. The heavenly bodies, he asserted, were masses of stone torn from the earth and ignited by rapid rotation. He explained that though both sun and the stars were fiery stones, we do not feel the heat of the stars because of their enormous distance from earth. He thought that the earth is flat and floats supported by 'strong' air under it and disturbances in this air sometimes causes earthquakes. These speculations made him vulnerable in Athens to a charge of impiety. Diogenes Laertius reports the story that he was prosecuted by Cleon for impiety, but Plutarch says that Pericles sent his former tutor, Anaxagoras, to Lampsacus for his own safety after the Athenians began to blame him for the Peloponnesian war.

Anaxagoras is famous for introducing the cosmological concept of Nous (mind), as an ordering force. He regarded material substance as an infinite multitude of imperishable primary elements, referring all generation and disappearance to mixture and separation respectively.>>

[neufer]

GRAIL twins Ebb and Flow to smash into moon today
Astrobob, December 17, 2012

<<At 5:28 p.m. (EST) today Dec. 17, the twin GRAIL (Gravity Recovery and Interior Laboratory) moon probes [Ebb and Flow] will be intentionally crashed into a mountaintop near the moon’s north pole. Now that the paired probes are nearly out of fuel, mission controllers have directed them to the far north of the moon to avoid unintentional crashes near something important like an Apollo landing site.

NASA will provide live commentary of the scheduled lunar surface impacts
beginning at 5 p.m. EST. Check out NASA TV or USTREAM to watch and listen.
"EEEEEEEEEEEEEEEEEEEEEEEEEK. BOOM!"

The Lunar Reconnaissance Orbiter (LRO) has already taken photos of the site before the crash
and will photograph it soon after to record Ebb and Flow’s impact craters.>>

[Beyond]

Shucky-darn I forgot all about that.

[neufer]

Click to play embedded YouTube video.

New Video Shows the GRAIL MoonKAM’s Final Looks at the Moon
Universe Today | Nancy Atkinson | 2013 Jan 10

GRAIL’s Stunning Parting Shots
Slate Blogs | Bad Astronomy | 2013 Jan 10

[bystander]

Remains of GRAIL Spacecraft Found on Lunar Surface
Universe Today | Nancy Atkinson | 2013 Mar 19

[i]Before and after the GRAIL twins impacts on the Moon December 17, 2012. The LROC Narrow Angle Camera (NAC) directors were able to resolve the impact sites on February 28, 2013, revealing both to be about 5 meters in diameter. Upper panels show the area before the impact; lower panels after the impact. Arrows point to crater locations. LROC NAC observations M186085512R, M186078336L, M1116736474R and M1116736474L. [b](Credit: NASA/GSFC/Arizona State University)[/b][/i]

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On December 17, 2012, the GRAIL mission came to an end, and the two washing machine-sized spacecraft performed a flying finale with a planned formation-flying double impact into the southern face of 2.5-kilometer- (1.5-mile-) tall mountain on a crater rim near the Moon’s north pole. The Lunar Reconnaissance Orbiter has now imaged the impact sites, which show evidence of the crashes.

But surprisingly, these impacts were not what was expected, says the LRO and GRAIL teams. The ejecta around both craters is dark. Usually, ejecta from craters is lighter in color – with a higher reflectance – than the regolith on surface.

“I expected the ejecta to be bright,” said LROC PI Mark Robinson at a press conference from the Lunar and Planetary Science Conference today, “because everybody knows impact rays on the Moon are bright. We are speculating it could be from hydrocarbons from the spacecraft.”

Typically ejecta from craters is brighter, since subsurface regolith tends to have a higher reflectance. The lunar regolith on the surface tends to be darker because of its exposure to the vacuum of space, and its exposure to cosmic radiation, solar wind bombardment, and micrometeorite impacts. Slowly over time, these processes tend to darken the surface soil.

Robinsons said they hydrocarbons could have come from fuel left in the fuel lines (JPL estimated a quarter to half a kilogram of fuel may have remained in the spacecraft – so not very much) or from the , spacecraft itself, which is made out of carbon material.

Additionally, the impact craters’ shapes were not as expected. The impacts formed craters about 5 m (15 ft) in diameter, and there is little ejecta to the south – the direction from which the spacecraft were traveling. “The spacecraft came in at a 1 or 2 degree impact angle,” said Robinson, “so this not a normal impact, as all the ejecta went upstream in the direction of travel.”

“I was expecting to see skid marks, myself,” said GRAIL principal investigator Maria Zuber. She added that she was committed to using every bit of fuel to mapping the gravity field at as low an altitude as possible. “I was determined that we would not end the mission with unused fuel because that would have meant we could mapped it even lower.

The spacecraft did end up being able to map the Moon from 2 km above the surface, the lowest altitude from which any planetary surface has ever been mapped, creating an extremely high resolution map.

Robinson said he was skeptical that they could find the impact craters, since the team has yet to find the impact sites of the Apollo ascent stages, which should be much bigger than the GRAIL impacts.

“Finding the impact crater was like finding a needle in haystack,” Robinson said, “as the images are looking at an area that is about 8 km wide and 30 to 40 km tall, and we were looking for something that is a couple of pixels wide.”

Robinson said he spent hours looking for it with no luck, only to see it later when he was on a conference call and was just looking at it out of the corner of his eye.

“It was really fun to find the craters,” he said.

While LRO’s camera was not able to image the actual impact since it occurred on the night-side of the Moon, the LAMP instrument (Lyman Alpha Mapping Project) on LRO was able to detect the plume of the impacts.

Kurt Rerhorford, PI of LAMP said the UV spectrograph was pointed towards the limb of the Moon to observe the gases coming out of the plumes. They did detect the two impact plumes which clearly showed an excess of emissions from hydrogen atoms. “We were excited to see this detection of atomic hydrogen coming from the impact sites,”Retherford said. “This is our first detection of native hydrogen atoms from the lunar environment.”

Retherford said further studies from this will help in determining the processes of how the implantation of solar wind protons on the lunar surface could create the water and hydroxyl that has been recently detected on the lunar surface by other spacecraft.

LRO Sees Grail's Explosive Farewell
NASA | JPL-Caltech | LRO | 2013 Mar 18

[neufer]

Remains of GRAIL Spacecraft Found on Lunar Surface
Universe Today | Nancy Atkinson | 2013 Mar 19

On December 17, 2012, the GRAIL mission came to an end, and the two washing machine-sized spacecraft performed a flying finale with a planned formation-flying double impact into the southern face of 2.5-kilometer- (1.5-mile-) tall mountain on a crater rim near the Moon’s north pole. The Lunar Reconnaissance Orbiter has now imaged the impact sites, which show evidence of the crashes. But surprisingly, these impacts were not what was expected, says the LRO and GRAIL teams. The ejecta around both craters is dark. Usually, ejecta from craters is lighter in color – with a higher reflectance – than the regolith on surface. “I expected the ejecta to be bright,” said LROC PI Mark Robinson at a press conference from the Lunar and Planetary Science Conference today, “because everybody knows impact rays on the Moon are bright. We are speculating it could be from hydrocarbons from the spacecraft.”

Were the two washing machine-sized spacecraft doing a dark load at the time

[bystander]

Were the two washing machine-sized spacecraft doing a dark load at the time

Probably a load of blue jeans (or some other dark matter) that became unbalanced.

[MargaritaMc]

Were the two washing machine-sized spacecraft doing a dark load at the time

Probably a load of blue jeans (or some other dark matter) that became unbalanced.

Nuns in convent I used to go to for R&R - over twenty years ago - had two large washing machines - known to all as Ebb and Flo...

[bystander]

Were the two washing machine-sized spacecraft doing a dark load at the time

Probably a load of blue jeans (or some other dark matter) that became unbalanced.

Nuns in convent I used to go to for R&R - over twenty years ago - had two large washing machines - known to all as Ebb and Flo...

So we now know where they came from and what the dark matter was that they contained.

[neufer]

--------------------------------------------

• King Henry IV, Part i Act 1, Scene 2

PRINCE HENRY: Thou sayest well, and it holds well too; for the
. fortune of us that are the moon's men doth EBB and
. FLOW like the sea, being governed, as the sea is,
. by the moon. As, for proof, now: a purse of gold
. most resolutely snatched on Monday night and most
. dissolutely spent on Tuesday morning; got with
. swearing 'Lay by' and spent with crying 'Bring in;'
. now in as low an ebb as the foot of the ladder
. and by and by in as high a flow as the ridge of the gallows.
--------------------------------------------

• Love's Labour's Lost Act 4, Scene 3

BIRON: Sweet lords, sweet lovers, O, let us embrace!
. As true we are as flesh and blood can be:
. The sea will EBB and FLOW, heaven show his face;
. Young blood doth not obey an old decree:
. We cannot cross the cause why we were born;
. Therefore of all hands must we be forsworn.
--------------------------------------------

• Romeo and Juliet Act 3, Scene 5

CAPULET: When the sun sets, the air doth drizzle dew;
. But for the sunset of my brother's son
. It rains downright.
. How now! a conduit, girl? what, still in tears?
. Evermore showering? In one little body
. Thou counterfeit'st a bark, a sea, a wind;
. For still thy eyes, which I may call the sea,
. Do EBB and FLOW with tears; the bark thy body is,
. Sailing in this salt flood; the winds, thy sighs;
. Who, raging with thy tears, and they with them,
. Without a sudden calm, will overset
. Thy tempest-tossed body. How now, wife!
. Have you deliver'd to her our decree?
--------------------------------------------

• King Lear Act 5, Scene 3

KING LEAR: No, no, no, no! Come, let's away to prison:
. We two alone will sing like birds i' the cage:
. When thou dost ask me blessing, I'll kneel down,
. And ask of thee forgiveness: so we'll live,
. And pray, and sing, and tell old tales, and laugh
. At gilded butterflies, and hear poor rogues
. Talk of court news; and we'll talk with them too,
. Who loses and who wins; who's in, who's out;
. And take upon's the mystery of things,
. As if we were God's spies: and we'll wear out,
. In a wall'd prison, packs and sects of great ones,
. That EBB and FLOW by the moon.
--------------------------------------------

• The Tempest Act 5, Scene 1

PROSPERO: Mark but the badges of these men, my lords,
. Then say if they be true. This mis-shapen knave,
. His mother was a witch, and one so strong
. That could control the moon, make FLOWS and EBBS,
. And deal in her command without her power.
. These three have robb'd me; and this demi-devil--
. For he's a bastard one--had plotted with them
. To take my life. Two of these fellows you
. Must know and own; this thing of darkness!
. Acknowledge mine.
--------------------------------------------

• Excerpts from the book Francis Bacon Our Shakespeare, 1902
  by Edwin Reed

<<In the second edition of Hamlet, 1604, we find the tides of the ocean attributed, in accordance with popular opinion, to the influence of the moon.

• "The moist star,
  Upon whose influence Neptune's empire stands,
  Was sick almost to doomsday with eclipse."--i. 1.

This was repeated in the third quarto, 1605; in the fourth, 1611; in the fifth or undated quarto; but in the first folio (1623), the lines were omitted. Why?

During the Christmas revels at Gray's Inn in 1594, Francis Bacon contributed to the entertainment, among other things, a poem in blank verse, known as the Gray's Inn Masque. It is full of those references to natural philosophy in which the author took so much delight, and especially on this occasion when Queen Elizabeth was the subject, to the various forms of attraction exerted by one body upon another in the world. Of the influence of the moon, he says:

• "Your rock claims kindred of the polar star,
  Because it draws the needle to the north;
  Yet even that star gives place to Cynthia's rays,
  Whose drawing virtues govern and direct
  The flots and re-flots of the Ocean."

(The masque is not in Bacon's name, but no one can read it and doubt its authorship. Bacon was the leading promoter of these revels.)

At this time, then, Bacon held to the common opinion that the moon controls the tides; but later in life, in or about 1616, he made an elaborate investigation into these phenomona, and in a treatise entitled De Fluxu et Refluxu Maris, definitely rejected the lunar theory.

" We dare not proceed so far as to assert that the motions of the sun or moon are the causes of the motions below, which correspond thereto; or that the sun and moon have a dominion or influence over these motions of the sea, though such kind of thoughts find an easy entrance into the minds of men by reason of the veneration they pay to the celesial bodies.

Whether the moon be in her increase or wane; whether she be above or under the earth; whether she be elevated higher or lower above the horizon; whether she be in the meridian or elsewhere; the ebb and flow of the sea have no correspondence with any of these phenomona."- Bacon's De Fluxu et Refluxu Maris.

In every edition of Hamlet published previously to 1616, the theory is stated and approved; in every edition published after 1616, it is omitted.

The titles are attributed to the influence of the moon in 'A Midsummer Night's Dream' and the 'Winter's Tale'; but both these plays were written long before the date of Bacon's change of opinion on the subject. The former we know was not revised by the author for publication in the folio; and we have no reason to believe that the latter, then printed for the first time, underwent any revision after 1616.

The same theory is stated, also, in 'King Lear' and the 'First Part of Henry IV'; but the tragedy was in existence in 1606, and the historical play considerably earlier. The 'Tempest' was written in 1613.

It should be added, however, that the spring or monthly tides were ascribed by Bacon to the influence of the moon.

The passage from ' Hamlet' has been restored to the text by modern editors.>>

[neufer]

Were the two washing machine-sized spacecraft doing a dark load at the time

Probably a load of blue jeans (or some other dark matter) that became unbalanced.

Nuns in convent I used to go to for R&R - over twenty years ago - had two large washing machines - known to all as Ebb and Flo...

So we now know where they came from and what the dark matter was that they contained.

Are you suggesting that the Moon is now inHabited

[bystander]

Are you suggesting that the Moon is now inHabited

If it is, I'm betting the habitats are no longer habitable.

[MargaritaMc]

Are you suggesting that the Moon is now inHabited

If it is, I'm betting the habitats are no longer habitable.

It is a long, long way to go to get a change of habit...

[bystander]

LRO’s LAMP ultraviolet spectrograph observes mercury and hydrogen in GRAIL impact plumes
Southwest Research Institute | 2013 Mar 26

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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.

"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.

In October 2009, LAMP observed the impact of NASA's Lunar Crater Remote Observation and Sensing Satellite (LCROSS), making the first confirmation of the presence of atomic mercury, molecular hydrogen and carbon monoxide, along with smaller amounts of calcium and magnesium. Based on the analysis of lunar samples from the Apollo missions, G.W. Reed, a chemist at the Argonne National Laboratory, predicted an enhancement of mercury near the poles and its permanently shaded regions as far back as 1999. However, the prediction went unnoticed until it was cited by the LAMP team in the scientific literature. The new mercury measurements are being used to study the migration process behind this enhancement.

"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.

[bystander]

GRAIL Solves Mystery of Moon's Surface Gravity
NASA | JPL-Caltech | GRAIL | MIT | Purdue | LRO | 2013 May 30

NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission has uncovered the origin of massive invisible regions that make the moon's gravity uneven, a phenomenon that affects the operations of lunar-orbiting spacecraft.

Because of GRAIL's findings, spacecraft on missions to other celestial bodies can navigate with greater precision in the future.

GRAIL's twin spacecraft studied the internal structure and composition of the moon in unprecedented detail for nine months. They pinpointed the locations of large, dense regions called mass concentrations, or mascons, which are characterized by strong gravitational pull. Mascons lurk beneath the lunar surface and cannot be seen by normal optical cameras.

GRAIL scientists found the mascons by combining the gravity data from GRAIL with sophisticated computer models of large asteroid impacts and known detail about the terrain and geologic evolution of the impact craters. The findings are published in the May 30 edition of the journal Science.

"GRAIL data confirm that lunar mascons were generated when large asteroids or comets impacted the ancient moon, when its interior was much hotter than it is now," said Jay Melosh, a GRAIL co-investigator at Purdue University in West Lafayette, Ind., and lead author of the paper. "We believe the data from GRAIL show how the moon's light crust and dense mantle combined with the shock of a large impact to create the distinctive pattern of density anomalies that we recognize as mascons."

Information about the terrain, or topography, of the moon's surface came from measurements made by NASA's Lunar Reconnaissance Orbiter (LRO). "The combination of GRAIL's high-resolution gravity measurements with LRO's precise topography is extremely powerful and provided a foundation for the mathematical modeling," said Greg Neumann, an LRO science team member at NASA's Goddard Space Flight Center in Greenbelt, Md.

The origin of lunar mascons has been a mystery in planetary science since their discovery in 1968 by a team at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. Researchers generally agree mascons resulted from ancient impacts billions of years ago. It was not clear until now how much of the unseen excess mass resulted from lava filling the crater or iron-rich mantle upwelling to the crust.

On a map of the moon's gravity field, a mascon appears in a target pattern. The bulls-eye has a gravity surplus. It is surrounded by a ring with a gravity deficit. A ring with a gravity surplus surrounds the bulls-eye and the inner ring. This pattern arises as a natural consequence of crater excavation, collapse and cooling following an impact. The increase in density and gravitational pull at a mascon's bulls-eye is caused by lunar material melted from the heat of a long-ago asteroid impact.

"Knowing about mascons means we finally are beginning to understand the geologic consequences of large impacts," Melosh said. "Our planet suffered similar impacts in its distant past, and understanding mascons may teach us more about the ancient Earth, perhaps about how plate tectonics got started and what created the first ore deposits."

This new understanding of lunar mascons also is expected to influence planetary geology well beyond that of Earth and our nearest celestial neighbor.

"Mascons also have been identified in association with impact basins on Mars and Mercury," said GRAIL principal investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. "Understanding them on the moon tells us how the largest impacts modified early planetary crusts."

The Origin of Lunar Mascon Basins - H. J. Melosh et al

• Science Express (online 2013 May 30) DOI: 10.1126/science.1235768

Moon’s Variable Gravity Came From Ancient Impacts
Universe Today | Elizabeth Howell | 2013 May 31