[meteorite-list] NASA finds extra-terrestrial amino-acids in Sudan meteorites

[Mike Hankey]

Rob,

Marc sent me this response after I posted the article:

"Yeah, apparently de novo synthesis.  Hot, carbon-rich gases in the
ureilite formed a small amount of amino acids in the meteorite as it
cooled. My bet is that it happened on metal surfaces which acted as a
catalyst, and it's not all that surprising.  All you need is an
appreciable amount of nitrogen in the source gas and you should get a
little bit of everything as it cools."

I got the impression from the article / marc that the heat happened a
long time ago during the meteorites original formation or metamorphose
and not during its atmospheric entry.

Mike

On Thu, Dec 30, 2010 at 4:41 PM, Matson, Robert D.
<ROBERT.D.MATSON at saic.com> 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
>