Article Posted on : - Feb 21, 2012

The image shows the largest of the newly detected graben found in highlands of the lunar farside. Photo: NASA/Goddard/Arizona State University/Smithsonian Institution.

WASHINGTON (BNS): NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft has sent new images indicating that the moon's crust is being stretched, forming minute valleys in a few small areas on the lunar surface.

A team of researchers analysing high-resolution images obtained by the Lunar Reconnaissance Orbiter Camera (LROC) show small, narrow trenches typically much longer than they are wide. This indicates the lunar crust is being pulled apart at these locations.

These linear valleys, known as graben, form when the moon's crust stretches, breaks and drops down along two bounding faults. A handful of these graben systems have been found across the lunar surface, according to a news report by NASA.

Scientists propose this geologic activity occurred less than 50 million years ago, which is considered recent compared to the moon's age of more than 4.5 billion years.

"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, and lead author of a paper on this research, was quoted as saying in the news report.

The weak contraction suggests that the moon, unlike the terrestrial planets, did not completely melt in the very early stages of its evolution. Rather, observations support an alternative view that only the moon's exterior initially melted forming an ocean of molten rock.

The graben were an unexpected discovery and the images provide contradictory evidence that the regions of the lunar crust are also being pulled apart.

"This pulling apart tells us the moon is still active. LRO gives us a detailed look at that process," said Richard Vondrak, LRO Project Scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.