[meteorite-list] And there's likely a crater in a crater in thecrater in the crater

From: Jerry Flaherty <grf2_at_meteoritecentral.com>
Date: Sat, 6 Mar 2010 11:41:07 -0500
Message-ID: <56EB844F4A0543B68044452D89B296BC_at_JerryPCwind7>

Did Noah PETRO really have ANY choice in becoming Geo or Lunar crustal
specialist? Was his path preordained??
Jerry Flaherty

--------------------------------------------------
From: "Darren Garrison" <cynapse at charter.net>
Sent: Saturday, March 06, 2010 8:49 AM
To: <meteorite-list at meteoritecentral.com>
Subject: [meteorite-list] And there's likely a crater in a crater in
thecrater in the crater

> http://www.msnbc.msn.com/id/35728750/ns/technology_and_science-space/
>
> Crater-in-a-crater may offer peek at moon guts
> Part of the Apollo Basin may expose a portion of the moon's deep crust
>
> A big crater inside a huge crater on the moon could offer a view of the
> lunar
> innards, scientists now say.
>
> Here's the setup: Shortly after the moon formed, it got whacked, big time.
> The
> result, an enormous crater called the South Pole-Aitken basin. It's almost
> 1,500
> miles across and more than five miles deep.
>
> The impact punched into the layers of the lunar crust, scattering that
> material
> across the moon and into space. The tremendous heat of the impact also
> melted
> part of the floor of the crater, turning it into a sea of molten rock.
> Story continues below ?advertisement | your ad here
>
> "This is the biggest, deepest crater on the moon - an abyss that could
> engulf
> the United States from the East Coast through Texas," exlained Noah Petro
> of
> NASA's Goddard Space Flight Center.
>
> But wait, there was more.
>
> Asteroid bombardment over billions of years has left the lunar surface
> pockmarked with craters of all sizes, and covered with solidified lava,
> rubble,
> and dust. Glimpses of the original surface, or crust, are rare, and views
> into
> the deep crust are rarer still.
>
> Now, scientists say a crater on the edge of the South Pole-Aitken basin
> may
> provide just such a view. Called the Apollo Basin and formed by the later
> impact
> of a smaller asteroid, it is about 300 miles across.
>
> "It's like going into your basement and digging a deeper hole," Petro
> said.
>
> "We believe the central part of the Apollo Basin may expose a portion of
> the
> moon's lower crust," he said. "If correct, this may be one of just a few
> places
> on the moon where we have a view into the deep lunar crust, because it's
> not
> covered by volcanic material as many other such deep areas are. Just as
> geologists can reconstruct Earth's history by analyzing a cross-section of
> rock
> layers exposed by a canyon or a road cut, we can begin to understand the
> early
> lunar history by studying what's being revealed in Apollo."
>
> Petro presented his research Thursday at the Lunar and Planetary Science
> meeting
> in Houston. It was done using the moon Mineralogy Mapper (M3), a NASA
> instrument
> on board India's Chandrayaan-1 lunar-orbiting spacecraft. Analysis of the
> light,
> or spectra, in images revealed that portions of the interior of Apollo
> have a
> similar composition to the impact melt in the South Pole-Aitken (SPA)
> basin.
>
> As you go deeper into the moon, the crust contains minerals have greater
> amounts
> of iron, the researchers explained in a statement. When the moon formed,
> it was
> largely molten. Minerals containing heavier elements, like iron, sank down
> toward the core, and minerals with lighter elements, like silicon,
> potassium,
> and sodium, floated to the top, forming the original lunar crust.
>
> "The asteroid that created the SPA basin probably carved through the crust
> and
> perhaps into the upper mantle," Petro said. "The impact melt that
> solidified to
> form the central floor of SPA would have been a mixture of all those
> layers. We
> expect to see that it has slightly more iron than the bottom of Apollo,
> since it
> went deeper into the crust. This is what we found with M3. However, we
> also see
> that this area in Apollo has more iron than the surrounding lunar
> highlands,
> indicating Apollo has uncovered a layer of the lunar crust between what is
> typically seen on the surface and that in the deepest craters like SPA."
>
> The lower crust exposed by Apollo survived the impact that created SPA
> probably
> because it was on the edge of SPA, several hundred miles from where the
> impact
> occurred, according to Petro.
>
> Both SPA and Apollo are estimated to be among the oldest lunar craters,
> based on
> the large number of smaller craters superimposed on top of them. As time
> passes,
> old craters get covered up with new ones, so a crater count provides a
> relative
> age; a crater riddled with additional craters is older than one that
> appears
> relatively clean, with few craters overlying it. As craters form, they
> break up
> the crust and form a regolith, a layer of broken up rock and dust, like a
> soil
> on the Earth.
>
> Although the Apollo basin is ancient and covered with regolith (what we
> call
> dirt on Earth), it still gives a useful view of the lower crust because
> the
> smaller meteorite impacts that create most of the regolith don't scatter
> material very far.
>
> "Calculations of how the regolith forms indicate that at least 50 percent
> of the
> regolith is locally derived," said Petro. "So although what we're seeing
> with M3
> has been ground up, it still mostly represents the lower crust."
>
> Earth was bombarded back then, too. But the record of the events have been
> folded back into our active planet or weathered away. On the moon, which
> is
> comparatively dead geologically, the record of scars remains.
>
> "The Apollo and SPA basins give us a window into the earliest history of
> the
> moon, and the moon gives us a window into the violent youth of Earth,"
> Petro
> said.
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Received on Sat 06 Mar 2010 11:41:07 AM PST