[meteorite-list] MESSENGER Revealing More Details About PlanetMercury

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 29 Sep 2011 17:31:25 -0500
Message-ID: <B3602267C7374477A901FC673CB6CF87_at_ATARIENGINE2>

An article that expands the implications of
this data is at:
http://www.space.com/13127-planet-mercury-revealed-nasa-messenger-spacecraft.html

It might be of use to someone trying to figure
what a Mercurian meteorite would be like:
"The composition of Mercury's surface is
substantially different from that of other
terrestrial planets, according to Messenger's
scans of the X-rays emanating from the
planet. For instance, Mercury's surface
possesses at least 10 times more sulfur,
or brimstone, than Earth or the moon...
The measured ratio of potassium, a volatile
element, to the non-volatile elements
thorium and uranium revealed levels
of volatile materials comparable to the
other terrestrial planets... Measurements
of gamma rays emanating from the planet's
surface also support theories that Mercury
originated from material comparable to that
of stony chondritic meteorites... Altogether,
this surface chemistry suggests the planet
formed from material now seen in certain
stony chondritic meteorites and cometary
dust particles... Nittler said. 'Our work is
showing that at some level, Mercury formed
from a different mix of these building
blocks than did the other terrestrial planets.' "

They don't say WHICH chondrites are the
"certain" stony chondritic meteorites, however.
Any guesses?

Let's Google Larry Nittler. Hmmm:
http://www.sciencemag.org/content/333/6051/1847.abstract
The abstract says: "the planet's surface differs
in composition from those of other terrestrial
planets. Relatively high Mg/Si and low Al/Si
and Ca/Si ratios rule out a lunarlike feldspar-
rich crust. The sulfur abundance is at least
10 times higher than that of the silicate portion
of Earth or the Moon, and this observation,
together with a low surface Fe abundance,
supports the view that Mercury formed from
highly reduced precursor materials, perhaps
akin to enstatite chondrite meteorites or
anhydrous cometary dust particles. Low Fe
and Ti abundances do not support the
proposal that opaque oxides of these elements
contribute substantially to Mercury's low and
variable surface reflectance."

Here's a more detailed account (from June, 2011,
with graphs) that speaks to what meteorites the
Mercurian surface might resemble:
http://planetary.org/blog/article/00003067/
" Other models proposed that it [Mercury] formed
from a specific kind of meteorite called CV chondrite
that are very very rich in metal. For the most part
these are not in detailed agreement with our
observations, but variants cannot be ruled out."
A polite way of saying "forget CV's."

Other models on which doubt is cast? A larger
version of Earth boiled down? No way. Mercury
stripped of crust by a giant impact? Well, that's
looking dubious, too.

Just waiting for more data...


Sterling K. Webb
-----------------------------------------------------------------
----- Original Message -----
From: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
Sent: Thursday, September 29, 2011 2:29 PM
Subject: [meteorite-list] MESSENGER Revealing More Details About
PlanetMercury


>
>
> Sept. 29, 2011
>
> Dwayne Brown
> Headquarters, Washington
> 202-358-1726
> dwayne.c.brown at nasa.gov
>
> Paulette Campbell
> Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
> 240-228-6792
> paulette.campbell at jhuapl.edu
>
>
> RELEASE: 11-330
>
> NASA SPACECRAFT REVEALING MORE DETAILS ABOUT PLANET MERCURY
>
> WASHINGTON -- NASA's MESSENGER spacecraft, the first to achieve orbit
> around Mercury, is providing scientists new information about the
> planet. The data show widespread flood volcanism similar to Earth,
> clearer views of Mercury's surface, the first measurements of its
> elemental composition, and details about charged particles near the
> planet.
>
> MESSENGER, or the MErcury Surface, Space ENvironment, GEochemistry,
> and Ranging spacecraft, conducted 15 laps through the inner solar
> system for more than six years before achieving the historic orbit
> insertion March 18. The new results are reported in seven papers
> published in Science magazine.
>
> "MESSENGER's instruments are capturing data that can be obtained only
> from orbit," says principal investigator Sean Solomon, of the
> Carnegie Institution of Washington. "Mercury has many more surprises
> in store for us as our mission progresses."
>
> Scientists for decades had puzzled over whether Mercury had volcanic
> deposits on its surface. New data show a huge expanse of volcanic
> plains surrounding the planet's north polar region. These continuous
> smooth plains cover more than six percent of the planet's total
> surface. The deposits appear typical of flood lavas, or huge volumes
> of solidified molten rock similar to those found in the northwest
> United States.
>
> "If you imagine standing at the base of the Washington Monument, the
> top of the lavas would be something like 12 Washington Monuments
> above you," said James Head of Brown University, the lead author of
> one of the papers.
>
> Scientists also have discovered vents or openings measuring up to 16
> miles (25 kilometers) across that appear to be the source of some of
> the large volume of very hot lava that has rushed across Mercury's
> surface carving valleys and creating teardrop-shaped ridges in the
> underlying terrain.
>
> New images reveal landforms on Mercury suggesting a previously
> unrecognized geological process. Images of bright areas appear to be
> small, shallow, irregularly shaped depressions. The science team
> adopted the term "hollows" for these features to distinguish them
> from other types of pits seen on Mercury. Hollows have been found
> over a wide range of latitudes and longitudes, suggesting that they
> are fairly common across Mercury.
>
> "Analysis of the images and estimates of the rate at which the hollows
> may be growing led to the conclusion that they could be actively
> forming today," says David Blewett of the Johns Hopkins University
> Applied Physics Laboratory (APL) in Laurel, Md., lead author of one
> of the reports.
>
> Scientists also now have observations of the chemical composition of
> Mercury's surface. The information is being used to test models of
> Mercury's formation and further study the relationship between the
> planet's tenuous atmosphere and surface makeup. Chemical measurements
> reveal a higher abundance of potassium than previously predicted.
>
> "These measurements indicate Mercury has a chemical composition more
> similar to those of Venus, Earth, and Mars than expected," says APL's
> Patrick Peplowski, lead author of one of the papers.
>
> MESSENGER also has collected the first global observations of plasma
> ions-- mostly sodium -- in Mercury's magnetosphere, the volume of
> space near the planet dominated by Mercury's magnetic field. These
> results reveal that Mercury's weak magnetosphere provides the planet
> very little protection from the gusty solar wind, resulting is a very
> hostile surface environment with extremes in space weather.
>
> "We were able to observe the formation process of these ions, and it's
> comparable to the manner by which auroras are generated in the
> Earth's atmosphere near polar regions," said Thomas Zurbuchen of the
> University of Michigan and lead author of one of the reports.
>
> MESSENGER was designed and built by APL. The lab manages and operates
> the mission for NASA's Science Mission Directorate (SMD) in
> Washington. The mission is part of NASA's Discovery Program, managed
> for SMD by the agency's Marshall Space Flight Center in Huntsville,
> Ala.
>
> For more information about the mission visit:
>
> http://www.nasa.gov/messenger
>
> -end-
>
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Received on Thu 29 Sep 2011 06:31:25 PM PDT