Lua está a encolher

moon shrinking

“Fotografias tiradas pela sonda Lunar Reconnaissance Orbiter (LRO), enviada pela Agência Espacial Americana – NASA, ao satélite, para investigar a órbita da Lua, revelaram que a circunferência da superfície lunar contraiu pelo menos cem metros, nos últimos mil milhões de anos.
As imagens revelaram 14 novas escarpas lobulares — pequenas formações que, até agora, acreditava-se terem sido originadas por falhas tectónicas. São as mais jovens formações do satélite e, de acordo com Watters, provavelmente estão presentes em toda a Lua. A análise sugere que as escarpas se formaram durante um período de contracção, quando a Lua congelou e encolheu. (…)”
Leiam no Ciência Hoje.
main craters

Inovação Tecnológica:
“A Lua está encolhendo.
A sonda lunar LRO (Lunar Reconnaissance Orbiter), da NASA, descobriu relevos e formações geológicas na Lua, nunca observados antes, que indicam que a Lua inteira está encolhendo ao longo de eras geológicas.
Não é um encolhimento que possa causar preocupações aos apaixonados – na verdade o encolhimento é tão pequeno que será difícil mensurá-lo com precisão – mas é um fenômeno inédito e que poderá ajudar no refinamento das teorias de formação da Lua.
“Um dos aspectos mais marcantes das escarpas lunares é sua jovem idade aparente,” disse Thomas Watters, do Museu Nacional de Aeronáutica e Espaço, dos Estados Unidos. “Falhas de compressão globalmente distribuídas e relativamente jovens mostram uma contração recente da Lua inteira, provavelmente devido ao resfriamento do interior lunar. A magnitude da contração é estimada em cerca de 100 metros no passado [geológico] recente. (…)”

main scarp

The New York Times:
“Over a Billion Years, Scientists Find, the Moon Went Through a Shrinking Phase.
In making the announcement, scientists were quick to add that the Moon has not shrunk by much, that the shrinking may have occurred over a billion years, and that the Moon will not shrink out of view in the future.
“The kind of radius change and shrinking we’re describing here is so small that you would never notice it,”
The same cooling and shrinking occurs within all planetary bodies; NASA’s Messenger spacecraft recently observed similar — and much larger — fractures on the planet Mercury.
Over the eons, the shrinkage for the Moon was only about 200 yards, the length of two football fields, out of a diameter of 2,160 miles.
The scientists believe that the ridges are young — for planetary geologists, a billion years old is young compared with the 4.5-billion-year age of the solar system — because the ridges cut across small, young craters, but no large craters appear on top of any of the ridges. Large impacts are much rarer and likely to be much more ancient. The ridges also look freshly carved in the moonscape.
Some ridges could be much younger than a billion years, Dr. Watters said, and the shrinking and cracking could be still occurring today. (…)”

Bad Astronomy:
“(…) Yesterday came the news that our natural satellite might have shrunk 100 meters in diameter in relatively recent geologic time.
The Lunar Reconnaissance Orbiter found a plethora of scarps across the lunar surface, far more than we knew about before.
These cliff-like features can appear on Earth from tectonic shifts, but there’s no continental drift on the moon.
Thus, the most likely explanation is: The moon shrunk
If it did, the surface would buckle under the pressure and create these scarps. Astronomers say that the gradual cooling of the moon’s interior probably caused the shrinkage.
Don’t worry about the tides disappearing, though. “Recent” means a different thing to geologists than to everyone else, and in this case it has taken a billion years for the moon to shrink in diameter just 0.003 percent. (…)”

“The Moon is shrinking!
Well, a little: new results from the Lunar Reconnaissance Orbiter indicate that over recent geological time, the Moon has shrunk by approximately 100 meters in diameter!
Shrinkage makes the most sense. The interior of the Moon is still warm from the leftover heat from its formation billions of years ago. Hundreds of kilometers of rock makes a pretty good insulator, so the Moon has cooled very slowly. As the interior cools, it shrinks, and the surface collapses down as well. Pressure builds, then snap! While a lot of these scarps are very long and dozens of meters in height, LRO’s sharp vision (it can see objects less than a meter in size!) can spot scarps that are only a kilometer or two in length and a few meters high.
does this process still continue today?
Maybe. The scarps seen are relatively young, something like 800 million to a billion years old. Dating them is difficult.
So, does this mean the process is still going on? It’s not really possible to say as yet. A billion years is a long time, and it’s difficult to know if any small scarps are younger than that. As LRO scans more and more of the lunar surface, more of these types of landscape features will be seen.
And finally, what does this mean for the ultimate size of the Moon? Well, you have to put this into perspective: the Moon’s diameter is about 3475 kilometers. This shrinkage is only about 0.003% of that. In other words, you’d never, ever be able to see that by comparing the Moon’s diameter now as it was, say, a billion years ago. So we’re not in any danger of the Moon collapsing down into a tiny little ball! (…)”

The Guardian:
“The moon is shrinking, say scientists!
Nasa orbiter finds telltale wrinkles on surface showing the moon has lost 200 metres from diameter.
Astronomers have declared that the moon is shrinking after spotting wrinkles all over the lunar surface. The tell-tale contraction marks were discovered by US scientists who examined thousands of photographs of the moon’s surface taken by a Nasa orbiter.
Some of the wrinkles are several miles long and rise tens of metres above the dusty terrain. Researchers believe they arise from the moon decreasing in size by around 200 metres across its diameter. The moon’s mean diameter is generally calculated to be 2,159 miles.
“Not only could they be indicating recent contraction of the moon, they may be indicating that the moon is still contracting,” said Watters. “Until now, we really had no evidence of cooling and the contraction of the moon that would go along with it. This isn’t anything to worry about. The moon may be shrinking, but not by much. It’s not going anywhere.” (…)”

“The moon is shrinking ever so slightly, but there is no cause for alarm, according to a new study that has discovered a clutch of previously unseen faults on the lunar surface from photos taken by a NASA probe.
In all, 14 previously undetected small thrust faults — the physical markers of contraction on the lunar surface — were found to be globally distributed around the moon in thousands of photos returned by NASA’s Lunar Reconnaissance Orbiter.
These fault structures — called lobate scarps — are among the youngest landforms on the moon. Their distribution across the lunar surface (as opposed to regional distribution) suggests that cooling in the moon’s interior is the likely cause of the contraction, or shrinkage”
“Lunar Reconnaissance Orbiter reveals incredible shrinking Moon.
Based on the size of the newly discovered cliffs, scientists estimate the distance between the Moon’s center and its surface has shrunk by about 300 feet.”

The Money Times:
“Moon has shrunk over a billion years, still shrinking.
Moon, the nearest heavenly body to earth, is shrinking, aver scientists. However, the quantum of shrinkage is so little that it is not apparent.
All that has shrunk of the moon is the length of two football fields and that too over a billion years.
Therefore, the probability that the moon will contract and disappear anytime soon is zilch.
Cooling led to shrinkage. The latest findings indicate that the interior of the moon has cooled, and as a result of this cooling, it has condensed and shrunk. The same cooling and shrinking occurs within all planetary bodies, aver scientists.”

Artigo Científico:
“Evidence of Recent Thrust Faulting on the Moon Revealed by the Lunar Reconnaissance Orbiter Camera
Thomas R. Watters, Mark S. Robinson, Ross A. Beyer, Maria E. Banks, James F. Bell III, Matthew E. Pritchard, Harald Hiesinger, Carolyn H. van der Bogert, Peter C. Thomas, Elizabeth P. Turtle, Nathan R. Williams
Aug. 20, 2010
Vol.: 329 – 936-940”

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