[meteorite-list] Show me the Shock

[ALAN RUBIN]

I am really surprised that a press release was issued on work that has not
even been submitted for peer-reviewed publication. There seems to be no age
data, no bulk chemical data, and no shock data. The authors seem to claim
it was launched off Earth just 10,000 years ago, but I don't know where
this comes from. Of course, there is no large terrestrial crater of that
age. If the crystallization age is 4.5 billion years, then it is not from
Earth. If the rock was launched from Earth, the required energy would melt
it. The rock is listed as an achondrite, so that part fits, but it would
have melted during launch 10,000 years ago (if that number is valid), not
billions of years ago. I remain skeptical and surprised at the precipitous
press release.

On Tue, Jul 25, 2023, 11:58 AM Robert Verish via Meteorite-list <
meteorite-list at meteoritecentral.com> wrote:

> https://www.space.com/boomerang-meteorite-left-earth-and-returned
>
> A dark reddish-brown stone, picked up from the Sahara desert in Morocco a
> few years ago, appears to be an Earth rock that was flung into space where
> it stayed for thousands of years before returning home ? surprisingly
> intact.
>
> If scientists are right about this, the rock will officially be named the
> first meteorite to boomerang from Earth. [Not for certain!]
>
> The discovery team's work was *presented*
> (
> https://conf.goldschmidt.info/goldschmidt/2023/meetingapp.cgi/Paper/20218
> )
> last week at an international geochemistry conference and has not yet been
> published in a peer-reviewed journal.
>
> "I think there is no doubt that this is a meteorite," said Frank Brenker, a
> geologist at the Goethe University Frankfurt in Germany, who was not
> involved with the new study. "It is just a matter of debate if it is
> really
> from Earth."  [But, still could be the other way around.]
>
> Early diagnostic tests show the unusual stone features the same chemical
> composition as volcanic rocks on Earth. Interestingly, however, a few of
> its elements seem to have been altered into lighter forms of themselves.
> These lighter versions are known to occur only upon interacting with
> energetic *cosmic rays* ( https://www.space.com/32644-cosmic-rays.html )
> in space, which provided one of two key pieces of evidence
> declaring the rock's trip beyond Earth, geologists say.
>
> Other pending measurements include unambiguous data about how much shock
> from the original impact the stone absorbed. This unique signature can be
> detected
> in the permanently altered microstructures of the mineral crystals forming
> the rock.
> Estimating the meteorite's shock levels is "something that can be checked
> or done
> in one hour or so max, using naked eyes," Ferrière said, "thus, not costly
> and a
> very important observation in this case."
>
> ( https://cdn.mos.cms.futurecdn.net/uh7CnCZNh4MNnFY78yR2ke.jpg )
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