ASTRONOMY NEWS 

Spacecraft Reveals Recent Geological Activity On The Moon

The Moon may have been ‘active’ in the recent past

 New images from NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft show the Moon’s crust is being stretched, forming minute valleys in a few small areas on the lunar surface. Scientists propose this geologic activity occurred less than 50 million years ago, which is considered recent compared to the Moon’s age of more than 4.5 billion years.

A team of researchers analyzing high-resolution images obtained by the Lunar Reconnaissance Orbiter Camera (LROC) show small, narrow trenches typically much longer than they are wide. This indicates the lunar crust is being pulled apart at these locations. These linear valleys, known as graben, form when the Moon’s crust stretches, breaks and drops down along two bounding faults. A handful of these graben systems have been found across the lunar surface.

“We think the Moon is in a general state of global contraction because of cooling of a still hot interior,” said Thomas Watters of the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum in Washington, and lead author of a paper on this research appearing in the March issue of the journal Nature Geoscience. “The graben tell us forces acting to shrink the Moon were overcome in places by forces acting to pull it apart. This means the contractional forces shrinking the Moon cannot be large, or the small graben might never form.”

The weak contraction suggests that the Moon, unlike the terrestrial planets, did not completely melt in the very early stages of its evolution. Rather, observations support an alternative view that only the Moon’s exterior initially melted forming an ocean of molten rock.

 In August 2010, the team used LROC images to identify physical signs of contraction on the lunar surface, in the form of lobe-shaped cliffs known as lobate scarps. The scarps are evidence the Moon shrank globally in the geologically recent past and might still be shrinking today. The team saw these scarps widely distributed across the Moon and concluded it was shrinking as the interior slowly cooled.

Based on the size of the scarps, it is estimated that the distance between the Moon’s center and its surface shrank by approximately 300 feet. The graben were an unexpected discovery and the images provide contradictory evidence that the regions of the lunar crust are also being pulled apart.

“This pulling apart tells us the Moon is still active,” said Richard Vondrak, LRO Project Scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “LRO gives us a detailed look at that process.”

As the LRO mission progresses and coverage increases, scientists will have a better picture of how common these young graben are and what other types of tectonic features are nearby. The graben systems the team finds may help scientists refine the state of stress in the lunar crust.

“It was a big surprise when I spotted graben in the far side highlands,” said co-author Mark Robinson of the School of Earth and Space Exploration at Arizona State University, principal investigator of LROC. “I immediately targeted the area for high-resolution stereo images so we could create a three-dimensional view of the graben. It’s exciting when you discover something totally unexpected and only about half the lunar surface has been imaged in high resolution. There is much more of the Moon to be explored.” Source: American Astronomical Society

Mars Rocks Indicate Recent Quakes, Volcanism On Red Planet

If life ever existed on Mars, then newly discovered mineral deposits on the flanks of a long-dead volcano would be a good place to dig for its remains.

Images of a Martian landscape offer evidence that the Red Planet’s surface not only can shake like the surface of Earth, but has done so relatively recently. If marsquakes do indeed take place, said the scientists who analyzed the high-resolution images, our nearest planetary neighbor may still have active volcanism, which could help create conditions for liquid water.

With High Resolution Imaging Science Experiment (HiRISE) imagery, the research team examined boulders along a fault system known as Cerberus Fossae, which cuts across a very young (few million years old) lava surface on Mars. By analyzing boulders that toppled from a Martian cliff, some of which left trails in the coarse-grained soils, and comparing the patterns of dislodged rocks to such patterns caused by quakes on Earth, the scientists determined the rocks fell because of seismic activity. The Martian patterns were not consistent with how boulders would scatter if they were deposited as ice melted, another means by which rocks are dispersed on Mars.

Gerald Roberts, an earthquake geologist with Birkbeck, an institution of the University of London, who led the study, said that the images of Mars included boulders that ranged from 2 to 20 meters (6.5 to 65 feet) in diameter, which had fallen in avalanches from cliffs. The size and number of boulders decreased over a radius of 100 kilometers
(62 miles) centered at a point along the Cerberus Fossae faults.

“This is consistent with the hypothesis that boulders had been mobilized by ground-shaking, and that the severity of the ground-shaking decreased away from the epicenters of marsquakes,” Roberts said.  The study, by Roberts and his colleagues, will be published Thursday in the Journal of Geophysical Research-Planets, a publication of the American Geophysical Union (AGU).

The team compared the pattern of boulder falls, and faulting of the Martian surface, with those seen after a 2009 earthquake near L’Aquila, in central Italy. In that event, boulder falls occurred up to approximately 50 km (31 miles) from the epicenter. Because the area of displaced boulders in the marsscape stretched across an area approximately 200 km (124 miles) long, the quakes were likely to have had a magnitude greater than 7, the researchers estimated.

By looking at the tracks that the falling boulders had left on the dust-covered Martian surface, the team determined that the marsquakes were relatively recent — and certainly within the last few percent of the planet’s history — because Martian winds had not yet erased the boulder tracks. Trails on Mars can quickly disappear — for instance, tracks left by NASA robotic rovers are erased within a few years by Martian winds, whereas other, sheltered tracks stick around longer. It is possible, the scientists concluded, that large-magnitude quake activity is still occurring on Mars.

The existence of marsquakes could be significant in the ongoing search for life on Mars, the researchers stated. If the faults along the Cerberus Fossae region are active, and the quakes are driven by movements of magma related to the nearby volcano, Elysium Mons, the energy provided in the form of heat from the volcanic activity under the surface of Mars could be able to melt ice. The resulting liquid water, they noted, could provide habitats friendly to life. Source: American Geophysical Union

( Last Week) Earth-Facing Sunspot Doubles in Size

 Animation of AR1416′s evolution over the past several days –  (SDO/HMI

The latest sunspot region to traverse the face of the Sun has nearly doubled in size as it aims Earthward, as seen in the animation above from NASA’s Solar Dynamics Observatory.  This is the second day in a row that the region has been seen expanding.

According to SpaceWeather.com, active region 1416 has the right sort of magnetic energy to potentially send M-class flares our way.

M-class flares are medium-sized solar flares. They can cause brief radio blackouts that affect Earth’s polar regions. Minor radiation storms sometimes follow an M-class flare event.

If AR1416 produces a flare over the next 24 hours we would likely see increased auroral activity in upper latitudes early next week.

Stay tuned to Universe Today and SpaceWeather.com for any news on solar flares, and be sure to visit the SDO site for the latest images and videos of our home star. Source: Universe Today.  Images courtesy NASA/SDO and the AIA and HMI science teams.

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