February 21, 2012
LRO Reveals Moon Is Still Being Pulled Apart
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NASA's Lunar Reconnaissance Orbiter (LRO) has revealed that the surface of the moon is actually being stretched.Researchers said the moon's surface is forming minute valleys in some small areas on the lunar surface.
They believe this activity occurred less than 50 million years ago, making it recent activity when considering the moon is over 4.5 billion years old.
The team studied high-resolution images taken by the Lunar Reconnaissance Orbiter Camera (LROC) during their research.
The images unveiled that the moon's crust is being pulled apart at these linear valleys, known as graben.
These valleys form when the moon's crust stretches, breaks and drops down along two bounding faults.
"We think the moon is in a general state of global contraction because of cooling of a still hot interior," Thomas Watters of the Center for Earth and Planetary Studies at the Smithsonian's National Air and Space Museum in Washington, said in a press release.
"The graben tell us forces acting to shrink the moon were overcome in places by forces acting to pull it apart. This means the contractional forces shrinking the moon cannot be large, or the small graben might never form."
The team used images in 2010 to identify physical signs of contraction on the lunar surface, in the form of cliffs known as lobate scarps.
The scarps give weight to theory that the moon shrank globally in the geologically recent past and might still be shrinking today.
They saw these scarps widely distributed across the moon and determined that it was shrinking as the interior cooled down.
The team estimates that the distance between the moon's center and its surface shrank by approximately 300 feet.
They were surprised to learn that the graben were still being pulled apart today, meaning the moon is still active.
"LRO gives us a detailed look at that process," Richard Vondrak, LRO Project Scientist at NASA's Goddard Space Flight Center, said in a press release.
The team may be able to use LRO and the graben systems to help scientists better understand the state of stress in the lunar crust.
"It was a big surprise when I spotted graben in the far side highlands," co-author Mark Robinson of the School of Earth and Space Exploration at Arizona State University said in a press release.
"I immediately targeted the area for high-resolution stereo images so we could create a three-dimensional view of the graben. It's exciting when you discover something totally unexpected and only about half the lunar surface has been imaged in high resolution."
The research will be published in the March issue of the journal Nature Geoscience.
Image 2: This shows the largest of the newly detected graben found in highlands of the lunar farside. The broadest graben is about 500 meters (1,640 feet) wide and topography derived from Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) stereo images indicates they are almost 20 meters (almost 66 feet) deep. (Credit: NASA/Goddard/Arizona State University/Smithsonian Institution)
Image 3: Graben are troughs formed when the lunar crust was stretched and pulled apart. This stretching causes the near-surface materials to break along two parallel normal faults, the terrain in between the twin faults drops down forming a valley. (Credit: Arizona State University/Smithsonian Institution)
On the Net:
- Lunar Reconnaissance Orbiter (LRO)
- Center for Earth and Planetary Studies
- Goddard Space Flight Center
- School of Earth and Space Exploration
- Nature Geoscience