Evidence for Young Lunar Volcanism
 
Oct 13, 2014:  NASA's Lunar Reconnaissance Orbiter (LRO) has provided
researchers strong evidence the moon's volcanic activity slowed gradually
instead of stopping abruptly a billion years ago. Scores of distinctive
rock deposits observed by LRO are estimated to be less than 100 million
years old. This time period corresponds to Earth's Cretaceous period, the
heyday of dinosaurs. Some areas may be less than 50 million years old.
 
"This finding is the kind of science that is literally going to make
geologists rewrite the textbooks about the moon," said John Keller,
LRO project scientist at NASA's Goddard Space Flight Center in Greenbelt,
Maryland.
 
http://www.nasa.gov/sites/default/files/14-284_0.jpg
 
The feature called Maskelyne is one of many newly discovered young volcanic
deposits on the Moon. Called irregular mare patches, these areas are
thought to be remnants of small basaltic eruptions that occurred much later
than the commonly accepted end of lunar volcanism, 1 to 1.5 billion years
ago. Image Credit: NASA/GSFC/Arizona State University
 
The deposits are scattered across the moon's dark volcanic plains and are
characterized by a mixture of smooth, rounded, shallow mounds next to
patches of rough, blocky terrain. Because of this combination of textures,
the researchers refer to these unusual areas as "irregular mare
patches."
 
The features are too small to be seen from Earth, averaging less than a
third of a mile (500 meters) across in their largest dimension. One of the
largest, a well-studied area called Ina, was imaged from lunar orbit by
Apollo 15 astronauts.
 
Ina appeared to be a one-of-a-kind feature until researchers from Arizona
State University in Tempe and Westf„lische Wilhelms-Universit„t M�nster in
Germany spotted many similar regions in high-resolution images taken by the
two Narrow Angle Cameras that are part of the Lunar Reconnaissance Orbiter
Camera, or LROC. The team identified a total of 70 irregular mare patches
on the near side of the moon.
 
The large number of these features and their wide distribution strongly
suggest that late-stage volcanic activity was not an anomaly but an
important part of the moon's geologic history.
 
The numbers and sizes of the craters within these areas indicate the
deposits are relatively recent. Based on a technique that links such crater
measurements to the ages of Apollo and Luna samples, three of the irregular
mare patches are thought to be less than 100 million years old, and perhaps
less than 50 million years old in the case of Ina. The steep slopes leading
down from the smooth rock layers to the rough terrain are consistent with
the young age estimates.
 
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In contrast, the volcanic plains surrounding these distinctive regions are
attributed to volcanic activity that started about 3 1/2 billion years ago
and ended roughly 1 billion years ago. At that point, all volcanic activity
on the moon was thought to cease.
 
Several earlier studies suggested that Ina was quite young and might have
formed due to localized volcanic activity. However, in the absence of other
similar features, Ina was not considered an indication of widespread
volcanism.
 
The findings have major implications for how warm the moon's interior is
thought to be.
 
"The existence and age of the irregular mare patches tell us that the
lunar mantle had to remain hot enough to provide magma for the small-volume
eruptions that created these unusual young features," said Sarah
Braden, a recent Arizona State University graduate and the lead author of
the study.
 
The new information is hard to reconcile with what currently is thought
about the temperature of the interior of the moon.
 
"These young volcanic features are prime targets for future
exploration, both robotic and human," said Mark Robinson, LROC
principal investigator at Arizona State University.
 
Details of the study are published online in the Oct. 12th edition of
Nature Geoscience.
 
Credits:
Production editor: Dr. Tony Phillips | Credit: Science{at}NASA
 
More information:
 
LRO is managed by Goddard for NASA's Science Mission Directorate at NASA
Headquarters in Washington. LROC, a system of three cameras, was designed
and built by Malin Space Science Systems and is operated by Arizona State
University.
 
To access the complete collection of LROC images, visit http://lroc.sese.asu.edu/
 
 
Regards,
 
Roger

--- D'Bridge 3.99