Earth's Moon is Rare Oddball

Space.com on Yahoo ^ | 11/20/07 | Dave Mosher

[NormsRevenge]

The moon formed after a nasty planetary collision with young Earth, yet it looks odd next to its watery orbital neighbor. Turns out it really is odd: Only about one in every 10 to 20 solar systems may harbor a similar moon.

New observations made by NASA's Spitzer Space Telescope of stellar dust clouds suggest that moons like Earth's are—at most—in only 5 to 10 percent of planetary systems.

"When a moon forms from a violent collision, dust should be blasted everywhere," said Nadya Gorlova, an astronomer at the University of Florida in Gainesville who analyzed the telescope data in a new study. "If there were lots of moons forming, we would have seen dust around lots of stars. But we didn't."

Gorlova and her team detail their findings in today's issue of the Astrophysical Journal.

Violent birth

Shortly after the sun formed about 4.5 billion years ago, scientists think a vagrant planet as big as Mars smacked into infant Earth and ripped off a chunk of our home's smoldering mantle. The rocky, dusty leftovers fell into orbit around our wounded planet, eventually coalescing into the moon we see today.

The scenario is unique among other moons in the solar system, which formed side-by-side with their planet or were captured by its gravity. Gorlova and her colleagues looked for the dusty signs of similar smash-ups around 400 stars, all about 30 million years old—roughly the age of our sun when Earth's moon formed.

Only one of all the stars they studied, however, displayed the telltale dust. Considering the frequency of planetary solar systems, the amount of time the dust should stick around and the window for moon-forming collisions to occur, the scientists were able to peg the frequency of extrasolar bodies that formed like our moon.

The estimate, however, is possibly a generous one.

"We don't know that the collision we witnessed around the one star is definitely going to produce a moon," said study co-author George Rieke, an astronomer at the University of Arizona in Tucson, "so moon-forming events could be much less frequent than our calculation suggests."

Odd moon out?

Planetary scientists like Gorlova and Rieke think infant solar systems can form moons between 10 and 50 million years after a star forms. That only a single star with collision-generated dust could be found in their latest research, the astronomers said, indicates that the 30 million-year-old stars in the study have finished making their planets.

"Astronomers have observed young stars with dust swirling around them for more than 20 years now," said Gorlova, noting that the dust could be collision-derived or primitive planet-forming material. "The star we have found is older, at the same age our sun was when it had finished making planets and the Earth-moon system had just formed in a collision."

While most the our type of moon may be rare, astronomers think there are billions of rocky planets out there with plenty of moons orbiting around them. The upshot for lunar lovers? There could be millions—or billions—of Earth-like moons drifting through the cosmos.

[NormsRevenge]

In an image released by the European Space Agency, the moon is photographed by the Rosetta spacecraft as it passes earth on Nov. 13, 2007.The European Space Agency's Rosetta spacecraft is the first mission designed to orbit and land on a comet. The mission consists of an orbiter and a lander, called Philae. The spacecraft carries 11 science experiments to complete the most detailed study of a comet ever attempted. Scientists hope that Rosetta will unlock the mysteries of how the Solar System evolved. (AP Photo/European Space Agency)

[LiteKeeper]

There is reasonable evidence to indicate the Moon did not come into existence through a collision with the Earth!

[irishtenor]

I think it ia an amazing bunch of balony.

[Southack]

Not a collision...

We got our Moon via a capture.

[muawiyah]

There was no Moon. Then a Mars sized planet smacked Earth. The residue tossed into orbit coalesced into the Moon. The other planet merged with Earth.

Could 'splain some of the Super Plumes under the Super Volcanos.

[Southack]

A collision should have some Earth material on the Moon, and some Moon material on Earth.

We see neither in amounts consistent with a collision.

Thus, we got our Moon via a capture.

[Sterm26]

I’ve never heard of a planet being referred to as a “vagrant”. Isn’t the PC term “homeless”?

[Dumpster Baby]

“Orbit Challenged”

[P8riot]

Genesis 1:14-19

14And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:

 15And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so.

 16And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also.

 17And God set them in the firmament of the heaven to give light upon the earth,

 18And to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good.

 19And the evening and the morning were the fourth day.

[NucSubs]

Good post Norm.

I believe the capture vs collision jury is still out.

[muawiyah]

What? Earth has been most of it's top most layers of light materials ever since the collision. That's why we have exposed ocean basins filled with basalt and continents of lighter weight limestone floating on top of it.

The Moon, on the other hand, is composed mostly of the same lightweight material that makes up the continents.

That was the clue to the analysis that resulted in a conclusion that Earth's former surface debris from a collision went into the creation of the Moon.

[muawiyah]

CORRECTION: "Earth has been MISSING most of it's top ...."

[Southack]

Basalt is just leftover lava. Lava flows on the seabed constantly.

Moon rocks are commonly called KREEPS because they contain Potassium (K) elements and Rare Earth Elements (REE) and Phosporus (P) not found in almost all rocks and mantle/crust of the Earth. Ditto for regolith. It’s on the Moon, not on the Earth.

Same again for Lunar norite, plagioclase, and pyroxene. Not exactly something you’d typically find on Earth (above or below our surface).

[RightWhale]

The moon is made of materials that would have been part of the crust of earth. The Pacific Ocean is the site of the borrow pit.

[Southack]

Where do we find norite on Earth?

[RightWhale]

It was all sucked into the moon.

[Southack]

Why would it all have been in the point of impact on Earth in the first place?

[RightWhale]

Not only that but there was a third body. The third body missed earth but not by much. We don’t know the composition of the third body, but it contained all those disconcerting lunar materials.

[muawiyah]

That's just from the surface where there's a vast amount of debris that's been brought in by meteors and comets.

The true composition of the Moon is known through inferential evaluation of it's size and density.

There are many things the Moon cannot be ~ e.g. a chunk of iron.

[SunkenCiv]

nuts, I didn’t notice that the other one was newer, and didn’t see this one before, so I posted a bunch of stuff.

http://www.freerepublic.com/focus/chat/1929042/posts?page=13#13

Earth’s Moon is ‘cosmic rarity’
BBC News | 21 November 2007 | Paul Rincon
Posted on 11/21/2007 4:12:51 PM EST by Aristotelian
http://www.freerepublic.com/focus/chat/1929042/posts