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Moon is shrinking and supermoon rare eclipse this month.

And it is the Earth’s gravitational force that is the culprit, reveals NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft.

After more than six years in orbit, NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft has revealed an astonishing fact — the moon is shrinking.

And the Earth’s gravitational force is the culprit.

The Lunar Reconnaissance Orbiter Camera (LROC) imaged nearly three-fourths of the lunar surface at high resolution, allowing the discovery of over 3,000 cliffs or faults known as “lobate scarps”.

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.

Earth’s gravity has influenced the orientation of thousands of faults that form in the lunar surface as the Moon shrinks.

In August, 2010, researchers using images from LRO’s Narrow Angle Camera (NAC) reported the discovery of 14 of these cliffs 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 10 kilometres 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.

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,” said 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,” said Watters, lead author of the research paper published in 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 modelled tidal and contractional forces is pretty striking,” said Watters.

In this March 19, 2011 photo, supermoon lights up the sky in Bangalore.

The total eclipse will last an hour and 12 minutes and will be visible to North and South America, Europe, Africa, and parts of West Asia and the eastern Pacific.

For the first time in more than 30 years, people in most parts of the world will witness a supermoon in combination with a total lunar eclipse on September 27.

The total eclipse will last an hour and 12 minutes and will be visible to North and South America, Europe, Africa, and parts of West Asia and the eastern Pacific.

Earth’s shadow will begin to dim the supermoon slightly, beginning at 8.11 p.m. EDT (5.41 a.m. IST, September 28, 2015).

Viewers can see the supermoon unmasked after nightfall. The total lunar eclipse will mask the moon’s larger-than-life face for more than an hour.

“Because the orbit of the moon is not a perfect circle, the moon is sometimes closer to the Earth than at other times during its orbit,” said Noah Petro, deputy project scientist at NASA’s Goddard Space Flight Centre in Greenbelt, Maryland.

“When the Moon is farthest away, it’s known as apogee and when it’s closest it’s known as perigee. On September 27, we are going to have a perigee full moon — the closest full moon of the year,” he said in a statement.

At perigee, the moon is about 50,000 km closer to earth than at apogee.

That distance equates to more than once around the circumference of earth.

Its looming proximity makes the moon appear 14 per cent larger and 30 per cent brighter in the sky than an apogee full moon, which sparked the term supermoon.

“There’s no physical difference in the moon. It just appears slightly bigger in the sky. It’s not dramatic, but it does look larger,” Mr. Petro added.

Despite its rarity, Mr. Petro said the event is not cause for concern.

“The only thing that will happen on Earth during an eclipse is that people will wake up the next morning with neck pain because they spent the night looking up,” he said and chuckled.

thanks to: The Hindu

dedicated by: KAVIGNAR THANIGAI.

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