Space

June 3, 2013

NASA’s GRAIL mission solves mystery of moon’s surface gravity

NASA’s Gravity Recovery and Interior Laboratory 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 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.”

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 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.”

Launched as GRAIL A and GRAIL B in September 2011, the probes, renamed Ebb and Flow, operated in a nearly circular orbit near the poles of the moon at an altitude of about 34 miles (55 kilometers) until their mission ended in December 2012. The distance between the twin probes changed slightly as they flew over areas of greater and lesser gravity caused by visible features, such as mountains and craters,

and by masses hidden beneath the lunar surface.

JPL managed GRAIL for NASA’s Science Mission Directorate in Washington. The mission was part of the Discovery Program managed at NASA’s Marshall Space Flight Center in Huntsville, Ala. NASA’s Goddard Space Flight Center, in Greenbelt, Md., manages the Lunar Reconnaissance Orbiter. Operations of the spacecraft’s laser altimeter, which provided supporting data used in this investigation, is led by the Massachusetts Institute of Technology in Cambridge.

Lockheed Martin Space Systems in Denver built GRAIL.

 




All of this week's top headlines to your email every Friday.


 
 

 

Headlines February 25, 2015

News: Army to send headquarters group to Kandahar in first sign of revision to Afghan withdrawal plan - In the first official sign that the Pentagon plans to keep a U.S. military presence in southern Afghanistan after this year, the Army is sending the 7th Infantry Division headquarters from Joint Base Lewis-McChord on a year-long deployment...
 
 

News Briefs February 25, 2015

Lithuania restores compulsory military service Lithuania will restore compulsory military service for young men as tensions in Ukraine continue to worry the small Baltic nation, the government said Feb. 24. After a meeting of military leaders and top government officials, President Dalia Grybauskaite said the measure was necessary because of growing aggression in Ukraine. Military...
 
 
Sensor Concepts Inc. photograph

Air Force Research Labís handheld imaging tool expands aircraft inspection capability

Sensor Concepts Inc. photograph An operator demonstrates the portability of the handheld imaging tool. The technology provides maintainers the ability to evaluate aircraft in the field to ensure mission-readiness. When pilots c...
 

 

Boeing, Royal Australian Air Force test extended range weapon

The Boeing Joint Direct Attack Munition Extended Range demonstrated significant range increase while maintaining its expected accuracy during flight testing conducted by Boeing and the Royal Australian Air Force. The testing centered on a new wing kit that, when used in conjunction with the weaponís guidance kit, increases the bomb’s range from approximately 15 miles...
 
 

DRS Technologies to provide comm systems for Royal New Zealand Navy frigates

DRS Technologies Inc., a Finmeccanica Company, announced Feb. 25 that its Canadian subsidiary will be providing tactical integrated communications systems to the New Zealand Ministry of Defense for the Royal New Zealand Navy’s ANZAC-class frigates. This subcontract was awarded to DRS Technologies Canada Ltd. in support of a communications modernization contract from Lockheed Martin Canada...
 
 

Northrop Grumman LITENING achieves two million operating hour milestone

In the life cycle of every military system, some milestones stand out as signature achievements. One million operating hours is one of them – and Northrop Grumman’s fielded AN/AAQ-28(V) LITENING pods have hit that number for the second time. “This is a significant milestone for the LITENING program and our team is proud to be...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>