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 August 18, 2014

News: U.S. mission in Iraq could expand, Pentagon official says - The mission for U.S. troops in Iraq to help Kurdish and Iraqi security forces in their fight against Islamic militants remains limited for now, but may expand after Iraqi leaders form a new government, a Pentagon spokesman said Aug. 19.   Business: Fuel deals top...
 
 

News Briefs August 20, 2014

Trials complete on fourth Coast Guard cutter Ingalls Shipbuilding in Pascagoula, Miss., has completed acceptance sea trials for the company’s fourth U.S. Coast Guard national security cutter, Hamilton. Jim French, Ingalls’ NSC program manager, tells The Mississippi Press) the Hamilton is scheduled to be delivered next month and commissioned on Dec. 6 in Charleston, South...
 
 
Army photograph by Sgt. Thomas Duval

Air Force, Army Aviation come together to complete vital mission in Egypt

Army photograph by Sgt. Thomas Duval Soldiers and airmen load a UH-60 Black Hawk into an Air Force C17 Globemaster III Aug. 19, 2104, at an old Israeli airstrip in the Sinai Peninsula of Egypt. The airstrip is now used by the M...
 

 
Air Force photograph by TSgt. Terri Praden

Joint effort validates ability to move Stryker vehicles via air

Air Force photograph by TSgt. Terri Praden An Army Stryker combat vehicle is guided into a C-17 Globemaster III during a 25th Infantry Division training exercise Aug. 13, 2014, at Joint Base Pearl Harbor-Hickam, Hawaii. The Str...
 
 
NASA image

Ozone-depleting compound persists, NASA research shows

NASA image Satellites observed the largest ozone hole over Antarctica in 2006. Purple and blue represent areas of low ozone concentrations in the atmosphere; yellow and red are areas of higher concentrations. NASA research show...
 
 

F-16V completes major capability milestone

The newest configuration of the F-16 Fighting Falcon, the F-16V, has reached a major capability milestone with the integration of a new Active Electronically Scanned Array radar. Completing this milestone on schedule demonstrates our ability to meet program commitments, said Roderick McLean, vice president and general manager of the F-16/F-22 Integrated Fighter Group at Lockheed...
 




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>