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

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sun, 12 Oct 2014 21:47:13 -0700 (PDT)
Message-ID: <201410130447.s9D4lDTS025761_at_zagami.jpl.nasa.gov>

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
Received on Mon 13 Oct 2014 12:47:13 AM PDT