Space

December 5, 2012

NASA twin spacecraft create most accurate gravity map of Moon

Twin NASA probes orbiting the 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 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 GRAIL co-investigator Mark Wieczorek of 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 both 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.”

While results from the primary science mission are just beginning to be released, the collection of gravity science by the lunar twins continues. GRAIL’s extended mission science phase began Aug. 30 and will conclude Dec. 17. As the end of mission nears, the spacecraft will operate at lower orbital altitudes above the moon.

When launched in September 2011, the probes were named GRAIL A and B. They were renamed Ebb and Flow in January by elementary students in Bozeman, Mont., in a nationwide contest. Ebb and Flow were placed in a near-polar, near-circular orbit at an altitude of approximately 34 miles (55 kilometers) on Dec. 31, 2011, and Jan. 1, 2012.

NASA’s Jet Propulsion Laboratory in Pasadena, Calif., manages the mission for NASA’s Science Mission Directorate in Washington. GRAIL is part of the Discovery Program managed at NASA’s Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems of Denver built the spacecraft.

 

To view the lunar gravity map, visit http://bit.ly/grailtour.

 




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


 
 

 

Headlines January 23, 2015

News: Two Marines identified in deadly California helo crash - Two Marine Corps officers killed when their helicopter crashed during a training exercise in the Southern California desert were remembered Jan. 25 as talented pilots. Greek F-16 crashes in Spain during NATO exercise - Ten people died Jan. 26 after a Greek air force F-16 jet crashed...
 
 

News Briefs January 26, 2015

Navy wants to increase use of sonar-emitting buoys The U.S. Navy is seeking permits to expand sonar and other training exercises off the Pacific Coast, a proposal raising concerns from animal advocates who say that more sonar-emitting buoys would harm whales. The Navy now wants to deploy up to 720 sonobuoys about 12 miles off...
 
 
Air National Guard photograph by SSgt. Annie Edwards

ANG conducts air refueling training with NATO allies in Germany

Air National Guard photograph by SSgt. Annie Edwards A NATO E-3A AWACS aircraft approaches a Utah Air National Guard KC-135R Stratotanker for air refueling during a training flight over Germany on Jan. 13, 2015. Nearly 30 airme...
 

 
Air Force photograph by SrA. Armando A. Schwier-Morales

Ramstein Airmen train with French air force

Air Force photograph by SrA. Armando A. Schwier-Morales Two U.S. Air Force pilots and a French air force navigator discuss the route to the drop zone during a simulated low-level drop Jan. 21, 2015, at Orleans – Bricy Air...
 
 

Marines receive first F-35C Lightning II carrier variant

The first F-35C Lightning II, carrier variant, for the U.S. Marine Corps touched-down on the flight line at Eglin Air Force Base, Fla., Jan. 13, from the Lockheed Martin plant in Fort Worth, Texas, to begin training in support of carrier-based operations. U.S. Marine Lt. Col. J.T. Ryan, Marine Fighter Attack Squadron 501 detachment commander...
 
 

VA announces single regional framework under MyVA initiative

The Department of Veterans Affairs announced Jan. 26 that it is taking the first steps under the MyVA initiative to realign its many organizational maps into one map with five regions to better serve Veterans. The new regions under the MyVA alignment will allow VA to begin the process of integrating disparate organizational boundaries into...
 




One 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>