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 October 24, 2014

News: U.S., South Korea delay transfer of wartime control - The U.S. and South Korea have delayed transferring wartime operational control of allied forces by taking on a “conditions-based approach” and scrapping the previously set deadline of 2015.   Business: Exclusive: Lockheed, Pentagon reach $4 billion deal for more F-35 jets - Lockheed Martin and U.S. defense...
 
 

News Briefs October 24, 2014

French moving troops toward Libyan border A top French military official says the country is moving troops toward the Libyan border within weeks and, along with U.S. intelligence, is monitoring al Qaeda arms shipments to Africa’s Sahel region. A French base will go up within weeks in a desert outpost just a hundred kilometers (60...
 
 
Navy photograph

Navy to commission submarine North Dakota

Navy photograph The PCU North Dakota (SSN 784) during bravo sea trials. The crew performed exceptionally well on both alpha and bravo sea trials. The submarine North Dakota is the 11th ship of the Virginia class, the first U.S....
 

 

Boeing announces SF Airlines order for Boeing converted freighters

Boeing announced Oct. 23 that SF Airlines has placed an order for an undisclosed number of 767-300ER passenger-to-freighter conversions (Boeing Converted Freighters). SF Airlines, a subsidiary of Shenzhen, China-based delivery services company SF Express, will accept its first redelivered 767 in the second half of 2015. “SF Express aims to become China’s most respected and...
 
 
LM-C130

Another Super Herc Little Rock Rollin’

  Lockheed Martin delivered another C-130J Super Hercules to the 61st Airlift Squadron at Little Rock Air Force Base, Ark., Oct. 23. Little Rock AFB’s new C-130J was ferried from the Lockheed Martin Aeronautics facility ...
 
 

United Technologies beats third quarter profit expectations

United Technologies Corp. Oct. 23 reported third-quarter profit of $1.85 billion as sales increased across all its businesses and the aerospace giant reported favorable tax settlements. The Hartford, Conn.,-based company said it had profit of $2.04 per share and earnings, adjusted for non-recurring gains, came to $1.82 per share. The results topped Wall Street expectations,...
 




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>