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Theory of study

New study complicates theory that ancient impact pierced Moon's crust The moon's largest and oldest impact crater likely doesn't have minerals from below the lunar crust on its surface, complicating a theory that an ancient massive impact event pierced the Moon's crust during the crater's formation, a new study finds. A study published earlier this year analyzed the way lunar materials reflect light to determine that a basin-forming impact that formed an ancient massive crater, the South Pole-Aitken basin, caused minerals from deep inside the Moon's mantle to rupture the Moon's surface. If mantle materials breached the lunar crust, studying them could yield significant clues about the Moon's history. Now, new research in the AGU journal Geophysical Research Letters reexamined the same data, acquired by the Chinese spacecraft Chang'E 4's rover, which landed in the crater in January 2019. The new study finds the crater's crust mainly consists of a common lunar crustal mineral not detected in earlier analyses. The new results suggest the basin floor may not have exposed lunar mantle material as previously reported. "We are not seeing the mantle materials at the landing site as expected," said Hao Zhang, a planetary scientist at the China University of Geosciences, Wuhan, China, and a co-author of the new study. The new study complicates theories about how the oldest, largest crater on Moon formed, adding to the body of knowledge about the Moon's history. Dating the South Pole-Aitken basin The South Pole-Aitken basin is considered one of the largest craters in the Solar System and the oldest on the Moon. The basin is 2,500 kilometers (1,553 miles) in diameter and runs roughly 13 kilometers (8 miles) deep. The basin resides on the Moon's far side, the enigmatic area facing away from Earth. It was untouched until Chang'E 4's landing in the crater in January 2019. Although scientists haven't radiometrically dated the basin's age yet, some estimates place its formation at 4.2 billion years ago. Scientists theorized the South Pole-Aitken basin-forming event ruptured the lunar crust, because of how deep the basin is today. Crustal topographic maps estimate the crust only extends 30 kilometers (19 miles) beneath the crater, whereas the rest of the lunar crust is 40 kilometers (25 miles) thick on average. The Moon was once covered in molten magma oceans. Over time, these cooled and separated into crust and mantle layers distinguished by many characteristics, including their mineral composition. Clinopyroxene, orthopyroxene, and olivine are all minerals associated with the Moon's mantle. They occasionally appear on the surface of the Moon, but large concentrations of them in a region could signal that the mantle once punctured the crust. Testing the crustal composition Spectroscopy is the study of how matter interacts with light. Minerals absorb specific wavelengths of light and color, which gives them unique signatures. Astrophysicists perform different types of spectroscopy to determine the composition and concentration of different materials on planetary bodies and their regions, based on these unique signatures. Previous research published in May in the journal Nature found concentrations of clinopyroxene, orthopyroxene, and olivine in the crater—amounts high enough to seemingly confirm the theory that the mantle had once breached the crust. The Nature study analyzed spectroscopic soil data from Chang'E 4 and processed the data using a series of functions. This process allowed them to identify the mathematically best fitting mineral for each's spectra compositions. Zhang and his colleagues also analyzed spectroscopic data acquired by instruments on Chang'E 4's rover after the spacecraft landed in the crater. They used a technique that compared the rover's documented reflections of light and color from the lunar surface to a database of known minerals. The database accounted for minerals' particle size, the way the minerals interact with light, and how they respond to space weathering—changes to the soil surface caused by solar wind irradiation and bombardment from tiny particles that the Moon's surface experiences. This different process allowed the researchers to detect and measure the amount of plagioclase in the crater. Plagioclase is a mineral created from cooling lava. It's also one of the most common rocks on the Moon's surface. The results showed plagioclase made up 56-72% of the crater's composition, making it the majority mineral. The high concentration of plagioclase suggests the lunar crust was not pierced by an ancient impact. The new study also found the landing site on the crater had concentrations of 9-28% orthopyroxene, 4-19% clinopyroxene, and 2-12% olivine. Although The three minerals are in the basin, they are not present at high enough amounts to prove an impact event once broke the crust, according to the study's authors. The new study complicates the certainty of earlier findings and points towards a need for continued research on the far side's lunar surface, according to Zhang. More information: Xiaoyi Hu et al. Mineral Abundances Inferred From In Situ Reflectance Measurements of Chang'E‐4 Landing Site in South Pole‐Aitken Basin, Geophysical Research Letters (2019). DOI: 10.1029/2019GL084531 This story is republished courtesy of AGU Blogs (http://blogs.agu.org), a community of Earth and space science blogs, hosted by the American Geophysical Union. Read the original story here. Citation: New study complicates theory that ancient impact pierced Moon's crust (2019, September 24) retrieved 6 October 2019 from https://phys.org/news/2019-09-complicates-theory-ancient-impact-pierced.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Visuospatial Abilities May Negatively Impact Theory of Mind in Parkinson, Study Says Cognitive status may be affected by the relationship of Parkinson disease (PD) and affective theory of mind through the involvement of visuospatial abilities (VSA), a recent study reported. A person’s theory of mind (ToM)—the ability to recognize others’ mental states—often deteriorates when they have Parkinson’s disease. Cognitive status may be affected by the relationship of Parkinson disease (PD) and affective ToM through the involvement of visuospatial abilities (VSA), according to a recent study. The study, published in Neuropsychiatric Disease and Treatment, involved 65 patients who were diagnosed with idiopathic PD and 51 controls who were matched for age, gender, and educational level. All participants completed a visual affective ToM task and their cognitive performance was assessed using the Montreal Cognitive Assessment. Psychiatric symptoms were also measured using the Brief Psychiatric Rating Scale (BPRS-E). “ToM is considered to be a complex neuropsychological ability, mediated by an elaborate neuroanatomical network, which includes the medial prefrontal cortex, the temporal lobe (superior temporal sulcus region and the temporal pole), the temporoparietal junction, and the amygdala,” explained the authors. “ToM abilities have been investigated in various neurodegenerative diseases, several studies showing impaired ToM performance in PD. Certain authors reveal deficits only regarding the cognitive aspect of ToM, while others also suggest supplementary reduced performance in the affective component of ToM.” The analysis revealed that affective ToM abilities were preserved in early PD patients yet declined as the disease progressed. Additionally, the researchers reported deficits in cognitive functioning predicted deficiencies in affective ToM. The relationship between PD and affective ToM were mediated by attention, executive functions, and VSA; however, only VSA impairment had a specific negative impact on affective ToM, according to the results. Therefore, the researchers noted that 41% of the total effects of attention and executive functions on affective ToM was mediated by visuospatial skills. “Attention deficits negatively impact on executive functions, which adversely influence visuospatial abilities, which in turn lead to affective ToM deficiencies. Although attention and executive functions do not act as individual mediators, they are part of an extended causal chain that ultimately involves visuospatial abilities,” concluded the authors. “Visuospatial skills may have a direct involvement in affective ToM impairments displayed by PD patients, as assessed with a visual task.” Reference Romosan A, Dehelean L, Romosan R, et al. Affective theory of mind in Parkinson’s disease: The effect of cognitive performance [published online August 30, 2019]. Neuropsychiatric Disease and Treatment. doi.org/10.2147/NDT.S219288. Related Articles Study casts doubt on important climate theory Sept. 23 (UPI) -- Until the release of greenhouse gases during the 20th century sent Earth's temperatures climbing, the planet was enjoying a 15-million-year-long period of cooling. What triggered that cooling has remained a matter of debate, but new research suggests one of the most popular theories is incomplete. Though temperatures have been rising over the last several decades as result of human-caused global warming, Earth's climate is cooler than it was 15 million years ago. The most agreed upon explanation for Earth's long-term cooling is enhanced rock weathering. Some 15 million years ago, the Indian and Asian continents collided, causing the formation of the Himalayas. The uplifting of Himalayas brought new rocks to the surface, enhancing rock weathering. Chemical processes involved in rock weathering sucked CO2 from the atmosphere -- so the thinking goes -- kicking off a 15-million-year-long period of cooling. New research, published Monday in the journal Nature Geoscience, suggests the enhanced rock weathering hypothesis is flawed. "The findings of our study, if substantiated, raise more questions than they answered," Yair Rosenthal, a distinguished professor of marine and coastal sciences at Rutgers University-New Brunswick, said in a news release. "If the cooling is not due to enhanced Himalayan rock weathering, then what processes have been overlooked?" For the study, researchers analyzed deep-sea sediments rich with calcium carbonate. Over millions of years, CO2 pulled from the atmosphere by rock weathering was carried by rivers to the ocean in the form of dissolved inorganic carbon. Algae used the carbon to synthesize their calcium carbonate shells. When the algae died, the shells sank to the ocean floor and became buried, trapping the ancient carbon. If weathering increased in the wake of the birth of the Himalayas, scientists surmised, deep-sea sediment cores should reveal a steady increase in calcium carbonate over the last several million years. But when scientists analyzed the results of dozens of deep-sea sediment core surveys, they found carbon and carbonate levels declined over the last 15 million years. Scientists determined algae called coccolithophores actually adapted to the dearth of CO2 by producing less calcium carbonate. According to the study, decreases in "weathering alkalinity inputs" resulted in diminished "carbonate accumulation." The study's authors are now studying the evolution of calcium and other elements in the oceans to better understand how and why Earth steadily cooled over the last 15 million years.



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