Did I miss the answers to these questions? Sorry if it's already been
answered. ;)
On 12/30/2010 1:59 PM, Meteorites USA wrote:
This raises some very interesting question. If the interior (core) of
the smaller stones from smaller meteorite falls such as Murchison,
Tagish Lake, Allende, Ash Creek, Mifflin, or any meteorite fall for
that matter, are still frozen during entry and upon impact, then would
it be a stretch of logic to assume a larger iron mass, such as Canyon
Diablo, which was estimated to be 50 meters wide, would also still
have a frozen core upon impact?
After all it did hold probably most of it's cosmic velocity, meaning
it was incandescent for just a few seconds at most, right? Even when
you consider iron conducts heat much faster and more efficiently than
stone, could such a large mass heat all the way to the core in just a
couple few seconds?
Regards,
Eric
On 12/30/2010 1:41 PM, Matson, Robert D. wrote:
Hi Mike and List,
Have been meaning to post a reply about the article link Mike posted:
http://www.digitaljournal.com/article/301636
I assume they are talking about Almahata Sitta. I had not heard this
before.
Yes, Almahata Sitta is right. As we all know, ET amino acids have been
found in plenty of carbonaceous meteorites, perhaps most famously
within Murchison. So I was curious to find out what was so special
about finding them in carbon-rich 2008 TC3 (Almahata Sitta). A quote
from the article:
"Amino-acids have been found in carbon-rich meteorites before but this
is the first time the acid substances have been found in a meteorite
as hot as 2,000 Fahrenheit (1,100c). This naturally heated hot rock
should have obliterated any form of organic material, reports National
Geographic.
Daniel Glavin, an astro-biologist at NASA's Goddard Space Flight
Centre in Maryland said, "Previously, we thought the simplest way to
make amino acids in an asteroid was at cooler temperatures in the
presence of liquid water, this meteorite suggests there's another way
involving reactions in gases as a very hot asteroid cools down."
So the obvious question to ask is why anyone thinks that the interior
of 2008 TC3 was ever heated up to 1100 C? Sure, the *surface* of the
asteroid got very hot when it entered earth's atmosphere, but how is
that different from Murchison or any other meteorite-generating fall?
The interior of 2008 TC3 should never have been above freezing.
So something must be missing from the article to explain why they
believe Almahata Sitta's interior got so hot. About all I can come
up with is that they assumed 2008 TC3 was a rubble pile (almost
certainly true given the range of petrology), and that it fragmented
into tiny pieces very high in the atmosphere while still moving at
cosmic velocity. Instead of heat from ablation only affecting the
outer centimeter or so of the surface of a 4-meter monolithic rock,
all the individual fragments got the blast treatment. I still don't
buy it, though. Small fragments decelerate so rapidly that there
wouldn't be time to heat up the interior of even a 1" diameter rock.
So the question is, am I missing something? --Rob
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