Ancient crater could hold clues about moon’s mantle

Researchers from Brown University and the University of Hawaii have found some mineralogical surprises in the Moon’s largest impact crater. Data from the Moon Mineralogy Mapper that flew aboard India’s Chandrayaan-1 lunar orbiter shows a diverse mineralogy in the subsurface…

Researchers from Brown University and the University of Hawaii have found some mineralogical surprises in the Moon’s largest impact crater.

Data from the Moon Mineralogy Mapper that flew aboard India’s Chandrayaan-1 lunar orbiter shows a diverse mineralogy in the subsurface of the giant South Pole Aitken basin. The differing mineral signatures could be reflective of the minerals dredged up at the time of the giant impact 4 billion years ago, the researchers say. If that’s true, then the South Pole Aitken (SPA) basin could hold important information about the Moon’s interior and the evolution of its crust and mantle.
The study, led by Brown graduate student Dan Moriarty, is published in online early view in the Journal of Geophysical Research: Planets.
At 2,500 kilometers across, the SPA is the largest impact basin on the Moon and perhaps the largest in the solar system. Impacts of this size turn tons of solid rock into molten slush. It has been assumed generally that the melting process would obliterate any distinct signatures of pre-existing mineralogical diversity through extensive mixing, but this latest research suggests that might not be the case.
The study looked at smaller craters within the larger SPA basin made by impacts that happened millions of years after the giant impact that formed the basin. Those impacts uncovered material from deep within the basin, offering important clues about what lies beneath the surface. Specifically, the researchers looked at the central peaks of four craters within the basin. Central peaks form when material under the impact zone rebounds, forming an upraised rock formation in the middle of the crater. The tops of those peaks represent pristine material from below the impact zone.
Using Moon Mineralogy Mapper data, the researchers looked at the light reflected from each of the four central peaks. The spectra of reflected light give scientists clues about the makeup of the rocks. The spectra showed substantial differences in composition from peak to peak. Some crater peaks were richer in magnesium than others. One of the four craters, located toward the outer edge of the basin, contained several distinct mineral deposits within its own peak, possibly due to sampling a mixture of both upper and lower crust or mantle materials.


The varying mineralogy in these central peaks suggests that the SPA subsurface is much more diverse than previously thought.
“Previous studies have suggested that all the central peaks look very similar, and that was taken as evidence that everything’s the same across the basin,” Moriarty said. “We looked in a little more detail and found significant compositional differences between these central peaks. The Moon Mineralogy Mapper has very high spatial and spectral resolution. We haven’t really been able to look at the Moon in this kind of detail before.”
The next step is figuring out where that diversity comes from.
It’s possible that the distinct minerals formed as the molten rock from the SPA impact cooled. Recent research from Brown and elsewhere suggests that such mineral formation in impact melt is possible. However, it’s also possible that the mineral differences reflect differences in rock types that were there before the giant SPA impact. Moriarty is currently undertaking a much larger survey of SPA craters in the hope of identifying the source of the diversity. If indeed the diversity reflects pre-existing material, the SPA could hold important clues about the composition of the Moon’s lower crust and mantle.
“If you do the impact scaling from models, [the SPA impact] should have excavated into the mantle,” Moriarty said. “We think the upper mantle is rich in a mineral called olivine, but we don’t see much olivine in the basin. That’s one of the big mysteries about the South Pole Aitken basin. So one of the things we’re trying to figure out is how deep did the impact really excavate. If it melted and excavated any material from the mantle, why aren’t we seeing it?”
If the impact did excavate mantle material, and it doesn’t contain olivine, that would have substantial implications for models of how the Moon was formed, Moriarty said.
Much more research is needed to begin to answer those larger questions. But this initial study helps raise the possibility that some of the original mantle mineralogy, if excavated, may be preserved in the Moon’s largest impact basin.
Carle Pieters, professor of geological sciences at Brown, and Peter Isaacson from the University of Hawaii were also authors on the paper. The work was supported by NASA’s Lunar Advanced Science and Exploration Research (LASER) program and the NASA Lunar Science Institute (NLSI).

Explore further:

Spectral analysis reveals Moon might have had water when it was formed

Provided by

Brown University

view popular

5 /5 (7 votes)

Related Stories

Biggest, Deepest Crater Exposes Hidden, Ancient Moon

Mar 04, 2010

(PhysOrg.com) — Shortly after the Moon formed, an asteroid smacked into its southern hemisphere and gouged out a truly enormous crater, the South Pole-Aitken basin, almost 1,500 miles across and more than …

Spectral analysis reveals Moon might have had water when it was formed

Aug 27, 2013

(Phys.org) —A research team with members from Johns Hopkins University Applied Physics Laboratory and the US Geological Survey has concluded that hydroxyl molecules found in the central peak of a crater …

Mineral analysis of lunar crater deposit prompts a second look at the impact cratering process

Apr 02, 2013

Large impacts on the Moon can form wide craters and turn surface rock liquid. Geophysicists once assumed that liquid rock would be homogenous when it cooled. Now researchers have found evidence that pre-existing …

Moon may harbour alien minerals, study says

May 26, 2013

Minerals found in craters on the Moon may be remnants of asteroids that slammed into it and not, as long believed, the satellite’s innards exposed by such impacts, a study said Sunday.

Researchers find evidence that moon’s Procellarum basin formed by asteroid strike

Oct 31, 2012

(Phys.org)—Researchers at Japan’s National Institute of Advanced Industrial Science and Technology propose in a paper published in the journal Nature Geoscience, that a strike by a large asteroid approx …

Two new NASA LRO videos: See moon’s evolution, take a tour

Mar 14, 2012

In honor of 1,000 days in orbit, the NASA Lunar Reconnaissance Orbiter (LRO) team at NASA Goddard Space Flight Center in Greenbelt Md. has released two new videos.

Recommended for you

Space station cooling breakdown may delay Orbital launch

2 hours ago

NASA rushed Thursday to fix a breakdown in the cooling system at the International Space Station that may delay the launch next week of Orbital Sciences’ first cargo mission.

Hubble discovers water vapor venting from Jupiter’s moon Europa

2 hours ago

The NASA/ESA Hubble Space Telescope has discovered water vapour erupting from the frigid surface of Jupiter’s moon Europa, in one or more localised plumes near its south pole.

Video: The Webb Space Telescope’s sunshield

4 hours ago

The newest video in the “Behind the Webb” series takes viewers behind the scenes to reveal how the pieces that make up each layer of the James Webb Space Telescope’s thin sunshield are bonded together.

Satellite’s magnetic mapping mission

4 hours ago

A scientist from the University of Liverpool will play a leading role in the European Space Agency’s (ESA) satellite mission to study the Earth’s geomagnetic field.

Morpheus project lander roars in free flight test

4 hours ago

What an otherworldly experience, without having to leave Earth! The Morpheus Project wrapped up a successful free-flight test yesterday. That picture above is just to whet your appetite for the actual video, …

NASA suspects bad valve for space station trouble (Update)

4 hours ago

The astronauts aboard the International Space Station dimmed the lights, turned off unnecessary equipment and put off science work Thursday as NASA scrambled to figure out what’s wrong with a key cooling …

User comments : 0

More news stories

First noble gas molecules discovered in space

Noble gas molecules have been detected in space for the first time in the Crab Nebula, a supernova remnant, by astronomers at UCL.

Hubble discovers water vapor venting from Jupiter’s moon Europa

The NASA/ESA Hubble Space Telescope has discovered water vapour erupting from the frigid surface of Jupiter’s moon Europa, in one or more localised plumes near its south pole.

Chinese flyby of asteroid shows space rock is “rubble”

China’s first flyby of an asteroid shows that a gigantic space rock which once triggered a doomsday scare is essentially rubble, scientists reported on Thursday.

Molecular clouds in the whirlpool galaxy appear to be embedded in fog

(Phys.org) —A multi-year study of the Whirlpool galaxy (M51) has changed our understanding of giant molecular clouds, in which stars are born. The new study, which mapped 1,500 such clouds, shows that, …

Fast radio bursts might come from nearby stars

First discovered in 2007, “fast radio bursts” continue to defy explanation. These cosmic chirps last for only a thousandth of a second. The characteristics of the radio pulses suggested that they came from …

Geologists report that risks of big earthquakes may be underestimated

(Phys.org) —Several geologists from around the world are presenting a case for missing or underreported earthquakes at this year’s American Geophysical Union Fall meeting being held in San Francisco. They …

Low-power tunneling transistor for high-performance devices at low voltage

A new type of transistor that could make possible fast and low-power computing devices for energy-constrained applications such as smart sensor networks, implantable medical electronics and ultra-mobile computing …

Keeping the lights on: Mechanical engineer finds a way to predict cascading power outages

A method of assessing the stability of large-scale power grids in real time could bring the world closer to its goal of producing and utilizing a smart grid. The algorithmic approach, developed by UC Santa …

Gift Guide: Strong slate of iPad challengers

Once upon a time, people who craved a tablet computer bought an iPad.

Mild 2013 cuts Arctic a break, warming woes remain (Update)

The rapid melting in the Arctic eased up this year. But the government says global warming is still dramatically altering the top of the world, reducing the number of reindeer and shrinking snow and ice, …