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.
Red areas on the topographic image indicate high elevations, and blue or purple areas indicate low elevation. The South Pole Aitken basin could hold clues about the composition of the Moon's mantle.
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).
Kevin Stacey | EurekAlert!
As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation
29.03.2017 | University of Hawaii at Manoa
Researchers discover dust plays prominent role in nutrients of mountain forest ecoystems
29.03.2017 | University of Wyoming
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Materials Sciences
29.03.2017 | Physics and Astronomy
29.03.2017 | Earth Sciences