Earth's Missing Moon -- NASA: "May Explain a Long-Standing Enigma"
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April 12, 2013

Earth's Missing Moon -- NASA: "May Explain a Long-Standing Enigma"

 

 

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NASA's GRAIL mission started its lunar probe late in 2011 to uncover some of the mysteries buried beneath the surface of the Moon --even, perhaps, a long-lost companion. According to recent scientific speculation, the Earth once had two moons gracing our night skies. 

"It's an intriguing idea," said David Smith, GRAIL's deputy principal investigator at MIT. "And it would be a way to explain one of the great perplexities of the Earth-Moon system – the Moon's strangely asymmetrical nature. Its near and far sides are substantially different."  The Moon's near side, facing us, is dominated by vast smooth 'seas' of ancient hardened lava. In contrast, the far side is marked by mountainous highlands. Researchers have long struggled to account for the differences, and the "two moon" theory introduced by Martin Jutzi and Erik Asphaug of the University of California at Santa Cruz is the latest attempt.

Scientists agree that when a Mars-sized object crashed into our planet about 4 billion years ago, the resulting debris cloud coalesced to form the Moon. Jutzi and Asphaug posit that the debris cloud actually formed two moons. A second, smaller chunk of debris landed in just the right orbit to lead or follow the bigger Moon around Earth.

"Normally, such moons accrete into a single body shortly after formation," explains Smith. "But the new theory proposes that the second moon ended up at one of the Lagrange points in the Earth-Moon system."

Lagrange points are a bit like gravitational fly traps. They can hold an object for a long time--but not necessarily forever. The second moon eventually worked its way out and collided with its bigger sister. The collision occurred at such a low velocity that the impact did not form a crater. Instead, the smaller moon 'went splat,' forming the contemporary far side highlands.In short, the lunar highlands are the lost moon's remains.

Flying in formation around the Moon, NASA's twin GRAIL spacecraft makes precise measurements of the lunar gravitational field. 

"By probing the Moon's gravity field, GRAIL  'sees' inside the Moon, illuminating the differences between the near and far sides."

GRAIL's twin spacecraft around the Moon for several months while a microwave ranging system precisely measures the distance between the two spacecraft. By watching that distance expand and contract as the pair fly over the lunar surface, researchers map the Moon's underlying gravity field.

These measurements tell us a lot about the distribution of material inside the Moon, and give us pretty definitive information about the differences in the two sides of the Moon's crust and mantle. If the density of crustal material on the lunar far side differs from that on the near side in a particular way, the finding will lend support to the 'two moon' theory."

But this information is just one "piece of the jigsaw puzzle." To prove a sister moon ever existed, other pieces are needed. NASA's Lunar Reconnaissance Orbiter has already provided key information on the Moon's surface topography. Scientists can also refer to lunar surface chemistry data and look at old seismic information from Apollo for clues.

But what's really needed, said Smith, is a sample return mission to the far side to determine the ages of rocks there.

"The smaller moon, if there was one, was about 1/3 the size of our current Moon. So upon collision it would have cooled down faster, and the rocks on the far side, where its remains are thought to have spread, would be older than the ones on the near side."


The Daily Galaxy via http://science.nasa.gov

Image credit: sciencewsblog.blogspot.com

 

Comments

J-C nobody cares... it's the information that really matters. Go run your own site since you demand "professional" standard or buy a subscription somewhere because this site is free. Expect errors, like Charles said almost nobody is perfect.

Quote: "Scientists agree that when a Mars-sized object crashed into our planet about 4 billion years ago, the resulting debris cloud coalesced to form the Moon".

AD: This is just a plain hypothesis, not a fact. It is even more just a disputed hypothesis amongst others.

Formation of planets cannot take place via "gravity and accretion". It takes strong magnetic fields that create enormous heat via the swirling effects that can be observed in galactic centres.

- The solar system is formed simultaneous in the galactic centre via the hydro-magnetic circuit in our galaxy where gasses and particles swirls into the galactic funnel ("black hole") and sorted out and melted together via the galactic core so called Z-Pinch. After this sorting out and melting gas and particles together in larger spheres, stars and planets are gently slung out via the galactic bars and further out in the galactic arms.

The only area where scientists can talk about cosmic collisions, regards the asteroid belts, but also these have had their collisions fairly early when the solar system was created in and near the galactic centre.

- It seems very contrary to claim that the whole solar system was created via simple accretion and gravity since the old debris in the asteroid belt still are hanging around with just a collision about every 10 million years.

BTW . . .
Quote: "GRAIL's twin spacecraft around the Moon for several months while a microwave ranging system precisely measures the distance between the two spacecraft. By watching that distance expands and contracts as the pair fly over the lunar surface, researchers map the Moon's underlying gravity field".

AD: The different distances between the twin spacecrafts can origin from all kind of fluctuated solar and other celestial pressures (or not) in the nearby celestial area.

So, I bet this "precisely measurement" later on will come up with different kinds of uncertainties and the usual anomalies.

Is that little moon 1/3 Luna's mass, or 1/3 it's diameter (1/27 the volume)?

@ Ivar - to be fair you can't know that hypothesis is true any more than this article can claim the accretion model; it is refreshing though to have an ulterior perspective on these issues. So, thank you kindly good sir!

http://news.uchicago.edu/article/2012/03/28/titanium-paternity-test-fingers-earth-moon-s-sole-parent

I like the sole parent idea, but as the article says the impactor could be identical to Earth. How could that happen?


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