[meteorite-list] LRO Mission Finds Widespread Evidence of Young Lunar Volcanism

[Ron Baalke]

October 12, 2014
    
NASA Mission Finds Widespread Evidence of Young Lunar Volcanism

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. Details of the study are published online in Sunday's 
edition of Nature Geoscience.

"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.

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 Westfallische Wilhelms-Universitat Munster 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.

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.

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/ 

For more information about LRO, visit:

http://www.nasa.gov/lro 

-end-

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov 

Nancy Neal-Jones/Elizabeth Zubritsky
Goddard Space Flight Center, Greenbelt, Md.
301-286-0039/301-614-5438
nancy.n.jones at nasa.gov / elizabeth.a.zubritsky at nasa.gov