[meteorite-list] Lutetia

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Sat, 12 Nov 2011 16:35:38 -0700
Message-ID: <3e9ddca739d94e8c2e8100cd37667acb.squirrel_at_webmail.lpl.arizona.edu>

Benjamin and Doug:

It has been a few years since I have done any spectroscopy of asteroids.
Also, I have not seen the Rosetta spectral results to be able to judge
what they are proposing. However, even as of a year ago, there was
uncertainty with respect to the spectral classification of Lutetia.
Originally, it fell into what was in the Tholen classification as EMP.
These asteroids have a slightly reddish spectral slope and no other
distinguishable features. The ambiguity in the class has to do with the
albedo and with that, I think Lutetia was classified as an M (moderate
albedo).

I just found the article that will be coming out in Icarus and the
spectral match does look very good. They do compare Lutetia with multiple
enstatite meteorites as well as other candidate meteorites and the match
is fairly good. I have not looked at the paper in detail, so I do not know
if there is spectral variation seen across the surface. You would expect
this for "a thin coating" on the surface.

I must admit that I was skeptical of the results based on the new
releases, but I am less so given the Icarus paper.

Larry

> Hey Benjamin
>
> Spectroscopy is one of many tools in the toolbox which unfortunately is
> not a good toolbox until you can scoop up a sample and look at it.
>
> This looks like you are responding to me since I mentioned paint in my
> reply of the difficulty of interpreting convoulted spectra made of
> billions of years of dust and collisions.
>
> But I'm not really sure because I called it speculation; so whoever you
> are talking about dismissing it, maybe they can speak up. An
> astronomer doing chemical spectras has a light path through earth's
> atmosphere, across space beyond Timbuctu to arrive at a sample that
> hasn't been cleaned for a few billion years and has been subjected to
> all varieties of meteoritical, asteroidal, cosmic particle, as well as
> the normal alteration processes.
>
> Then he has a collection of meteorites which is probably far from
> complete, but he is lucky if by chance one of them fairly matches after
> he does his best to cheat by starting with the meteorite fresh cut
> spectrum assuming it is his best match and working his way backwards
> doing what he can along the way to lower this peak or raise that one
> and then when all the dust is cleared :-), he just shows his spectrum
> of the asteroid and his spectrum of the meteorite after his series of
> manipulations and says Eureka, I've found it!
>
> The down side is minimal, the astronomer doesn't even get much of an
> academic spanking and speculation is healthy and fun. If he happens to
> be clever and lucky though, the upside is it really is a match and he
> goes down as the guy who discovered the composition of an asteroid or
> asteroid class.
>
> In the case of Lutetia, a closer view from Rosetta was significant
> becuase it eliminated many erroneous conclusions from other spectra of
> it that had been taken from Earth distance and it confirmed there are
> no organic materials, and water is scarce.
>
> Basically, after gravitational measurements, a different tool than
> spectroscopic ones is added, and it shows Lutetia is heave for its size
> does the idea it has a lot of metal start sounding good. But to say it
> is an E-meteorite class instead, for example of a Bencubbinite or
> perhaps one of the many types of millions of asteroids that we have not
> seen specimens from ... it's a real concrete jungle out there ...
>
> So, speculative is the correct word to use. And after reviewing the
> limitations of the spectroscopy, let's paint the town with it.
>
> Most interesting to me was the very large crater found. Now, luckily
> the Spectrum of Lutetia is rather unique. I the case of Vesta, the
> scale fell in favore of it being understood as the HED source after a
> chain of Vestoids was found spanning Vesta's orbit to a Kirkwood gap.
> In the case of Lutetia, let's see if the 10 million kilometers it needs
> to span have any baby Parisians along a path in an analolgous
> manner...Verrrrrrrrry interrrresting, but ... not stupid!
>
> Kindest wishes
> Doug
>
>
> -----Original Message-----
> From: Benjamin P. Sun <bpsun2009 at gmail.com>
> To: meteorite-list <meteorite-list at meteoritecentral.com>
> Sent: Sat, Nov 12, 2011 3:32 pm
> Subject: Re: [meteorite-list] Lutetia
>
>
> Regolith is mostly powdered rock and pebbles from the parent body that
> may or may not be compacted at the surface.
> So why should the reflectance spectra from Lutetia's regolith be
> totally dismissed? Are you dismissing Spectroscopy of asteroids
> altogether?
> If the "paint" derived from the parent body, then analysis of the
> "paint" could possibly tell us something about the parent body itself.
> Yes?
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Received on Sat 12 Nov 2011 06:35:38 PM PST