Nav: Home

NASA's LRO discovers Earth's pull is 'massaging' our moon

September 15, 2015

Earth's gravity has influenced the orientation of thousands of faults that form in the lunar surface as the moon shrinks, according to new results from NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft.

In August, 2010, researchers using images from LRO's Narrow Angle Camera (NAC) reported the discovery of 14 cliffs known as "lobate scarps" on the moon's surface, in addition to about 70 previously known from the limited high-resolution Apollo Panoramic Camera photographs. Due largely to their random distribution across the surface, the science team concluded that the moon is shrinking.

These small faults are typically less than 6.2 miles (10 kilometers) long and only tens of yards or meters high. They are most likely formed by global contraction resulting from cooling of the moon's still hot interior. As the interior cools and portions of the liquid outer core solidify, the volume decreases; thus the moon shrinks and the solid crust buckles.

Now, after more than six years in orbit, the Lunar Reconnaissance Orbiter Camera (LROC) has imaged nearly three-fourths of the lunar surface at high resolution, allowing the discovery of over 3,000 more of these features. These globally distributed faults have emerged as the most common tectonic landform on the moon. An analysis of the orientations of these small scarps yielded a surprising result: the faults created as the moon shrinks are being influenced by an unexpected source--gravitational tidal forces from Earth.

Global contraction alone should generate an array of thrust faults with no particular pattern in the orientations of the faults, because the contracting forces have equal magnitude in all directions. "This is not what we found," says Smithsonian senior scientist Thomas Watters of the National Air and Space Museum in Washington. "There is a pattern in the orientations of the thousands of faults and it suggests something else is influencing their formation, something that's also acting on a global scale -- 'massaging' and realigning them." Watters is lead author of the paper describing this research published in the October issue of the journal Geology.

The other forces acting on the moon come not from its interior, but from Earth. These are tidal forces. When the tidal forces are superimposed on the global contraction, the combined stresses should cause predictable orientations of the fault scarps from region to region. "The agreement between the mapped fault orientations and the fault orientations predicted by the modeled tidal and contractional forces is pretty striking," says Watters.

"The discovery of so many previously undetected tectonic features as our LROC high-resolution image coverage continues to grow is truly remarkable," said Mark Robinson of Arizona State University, coauthor and LROC principal investigator. "Early on in the mission we suspected that tidal forces played a role in the formation of tectonic features, but we did not have enough coverage to make any conclusive statements. Now that we have NAC images with appropriate lighting for more than half of the moon, structural patterns are starting to come into focus."

The fault scarps are very young - so young that they are likely still actively forming today. The team's modeling shows that the peak stresses are reached when the moon is farthest from Earth in its orbit (at apogee). If the faults are still active, the occurrence of shallow moonquakes related to slip events on the faults may be most frequent when the moon is at apogee. This hypothesis can be tested with a long-lived lunar seismic network.

"With LRO we've been able to study the moon globally in detail not yet possible with any other body in the solar system beyond Earth, and the LRO data set enables us to tease out subtle but important processes that would otherwise remain hidden," said John Keller, LRO Project Scientist at NASA's Goddard Space Flight Center, Greenbelt, Maryland.

Launched on June 18, 2009, LRO has collected a treasure trove of data with its seven powerful instruments, making an invaluable contribution to our knowledge about the moon. LRO is managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland, under the Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville for the Science Mission Directorate at NASA Headquarters in Washington, DC.
-end-


NASA/Goddard Space Flight Center

Related Lunar Surface Articles:

Digging into the far side of the moon: Chang'E-4 probes 40 meters into lunar surface
A little over a year after landing, China's spacecraft Chang'E-4 is continuing to unveil secrets from the far side of the Moon.
One small grain of moon dust, one giant leap for lunar studies
Scientists have found a new way to analyze the chemistry of the moon's soil using a single grain of dust brought back by Apollo 17 astronauts in 1972.
New research sheds light on the ages of lunar ice deposits
The discovery of ice deposits in craters scattered across the Moon's south pole has helped to renew interest in exploring the lunar surface.
Study suggests ice on lunar south pole may have more than 1 source
New research sheds light on the ages of ice deposits reported in the area of the Moon's south pole -- information that could help identify the sources of the deposits and help in planning future human exploration.
Reconstructing the first successful lunar farside landing
A research team, headed by Prof. LI Chunlai from the National Astronomical Observatories of Chinese Academy of Sciences has published a full reconstruction of the Chang'E-4's landing.
NASA's LRO sheds light on lunar water movement
Scientists using an instrument aboard LRO observed water molecules moving around the dayside of the moon.
NASA's Solar Dynamics Observatory catches lunar freeze frame
On March 6, NASA's Solar Dynamics Observatory watched a lunar transit in space -- one in which the satellite's path made the Moon appear to stand still, then backtrack.
First look: Chang'e lunar landing site
On Jan. 30, NASA's Lunar Reconnaissance Orbiter caught views of the Chinese Chang'e 4 lander on the floor of the Moon's Von Kármán crater.
Scientists explain formation of lunar dust clouds
Physicists from the Higher School of Economics and Space Research Institute have identified a mechanism explaining the appearance of two dusty plasma clouds resulting from a meteoroid that impacted the surface of the Moon.
Lunar craters named in honor of Apollo 8
The Working Group for Planetary System Nomenclature of the International Astronomical Union has today officially approved the naming of two craters on the Moon to commemorate the 50th anniversary of the Apollo 8 mission.
More Lunar Surface News and Lunar Surface Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.