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Rock Dating Experiments, Feasibility?
Stephen
post Mar 17 2005, 07:41 AM
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I notice they haven't included among MSL's experiment package any that might be used to date rocks, presumably because such a thing would be too heavy and/or consume too much power.

What I was wondering was how much would such an experiment weigh? Is it ever likely such a tool will ever be sent to Mars on a robot? For that matter, is any ever likely to be sent with a manned mission? Or is that the sort of experiment that will probably still only be possible in a lab on Earth even a decade or two from now?

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Stephen
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Marcel
post Mar 17 2005, 10:27 AM
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Started that topic before, though no reaction. Anyway, i think it is very important to asses the geological context of rocks by dating them. There are a lot of ways to do that with a variety of instruments. One example is the combination of a tightly focussed ion beam that vaporates tiny amounts of the mineral via a micro probe (shouldn't be that heavy !). The airborne particles on their turn can be analysed on composition by a specialized (heavy component) mass spectrometer. Samples need to be crushed and homogenized before it can be done though. So, we're talking about a crusher, a mixer (which can be done in one unit), an ion source (and feeding) and the spectrometer. And, off course, a way to clean the whole thing afterwards.

To my opinion, MSL must have it !
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djellison
post Mar 17 2005, 10:59 AM
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Well - MSL's initial payload is already determined - unlikely to shift.

but - let's answer this question ourselves.

1) How do you date a rock

2) What data does that require

3) What instrumentation gets that data

4) How flyable is that instrumentation

I'm a space nut, not a geologist, but thats the way to go thru it.

If anyone answers '1' with "Buy it flowers and take it to the cinema" I'll throw a chunk of granite at them.

Doug
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chris
post Mar 17 2005, 12:45 PM
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I'm not a geologist, but a quick Google tells me that rocks are dated use radiometry (the measure of the ratios of the products of radioactive decay). This requires a mass spectrometer, some means of vaporisizing bits of the sample, and some means for ensuring that you don't get cross-contamination between specimens (assuming you are doing more than one).

Mass spectrometers have been flying on lots of spacecraft (there are currently two on Mars in the Viking landers), so I would guess that the sample handling and cross-contamination issues would be paramount.

One other link http://earth.leeds.ac.uk/dynamicearth/dating/ says that "In practice great care is necessary in applying isotopic methods to date rocks".

Chris
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djellison
post Mar 17 2005, 02:25 PM
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Might this hack it on MSL then?

"Sample Analysis at Mars with an integrated suite consisting of a gas chromatograph mass spectrometer, and a tunable laser spectrometer," Paul Mahaffy, NASA's Goddard Space Flight Center, Greenbelt, Md. This instrument would perform mineral and atmospheric analyses, detect a wide range of organic compounds and perform stable isotope analyses of organics and noble gases.

If you google for it - lots od PDF's about, including one which says

(6) relative abundances of refractory elements, to trace levels, in solid phase samples.
From http://216.239.59.104/search?q=cache:KMPNx...lient=firefox-a


Doug
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chris
post Mar 17 2005, 03:20 PM
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Well, it can do:

(1) abundances of trace atmospheric species such as noble gases and certain small molecules (CH4, H2S,etc.);
(2) high-precision isotope ratios in key atmospheric species, such as the noble gases, C in CO2, N in N2, and D/H in H2O; identities, isotope ratios, and possible chirality of (3) relatively volatile organics and (4) pyrolyzable inorganic species, characteristic of specific mineralogies, in solid phase samples; (5) identities of moderate to high mass refractory organics; and
(6) relative abundances of refractory elements, to trace levels, in solid phase samples.

Whether or not it has the resolution to see the very small relative differences in the mass between different isotopes of the elements need for mineralogical datingis another question (the percentage difference in mass between D and H is much, much, greater than the difference between Lead-206 and Lead-207).

Chris
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Marcel
post Mar 17 2005, 03:24 PM
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QUOTE (djellison @ Mar 17 2005, 10:59 AM)
Well - MSL's initial payload is already determined - unlikely to shift.

but - let's answer this question ourselves.

1) How do you date a rock

2) What data does that require

3) What instrumentation gets that data

4) How flyable is that instrumentation

I'm a space nut, not a geologist, but thats the way to go thru it.

If anyone answers '1' with "Buy it flowers and take it to the cinema" I'll throw a chunk of granite at them.

Doug

Let's put it another way:

Questions:
1 What components/properties must a dating intrument have ?
2 What instruments are going to fly MSL anyway ?

Answers:
1 Sample collector & crusher / vaporizer (ion-beam or laser) / mass spectrometer
2 all of the above.

The only (not unimportant) aspect is indeed: initial payload is determined allready and modifications to the new (dating) purpose will be considerable.

But why not reconsider this though ? Especially because the mission is likely to be postponed until 2011 ! "Plenty" of time, one should say......I am sure the "Squyres and Golombeks" would LOVE to get this data.

Anyone with the right connections that will make the device fly...
gets a mars bar the size of MSL laugh.gif
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tedstryk
post Mar 17 2005, 03:36 PM
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I would caution that it is important that a rock dating device be precise. We can infer a very rough outline of Martian dates from meteorites and compositional studies to try to figure out where such meteorites came from. A date plus or minus a billion years isn't going to help much. But if an instrument can be designed that is small enough to fly that can produce useful age data of high enough quality to establish a "ground truth," that would be excellent.


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Marcel
post Mar 17 2005, 04:02 PM
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I agree.

An error of max. 5-10% would be "fine" though.

What i do know about the most sophisticated methods (labs on earth) of dating, is an accuracy of 0,1 %, considering samples between 100 and 1000 Myears !

What i don't know is: will engineers be able to get a Jaguar into a shoe box ?
Maybe we ask the Japanese ?
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djellison
post Mar 17 2005, 04:07 PM
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QUOTE (Marcel @ Mar 17 2005, 03:24 PM)
I am sure the "Squyres and Golombeks" would LOVE to get this data.

Oh - I'm sure they would. But the data the instruments they're flying instead they probably love even more smile.gif

Doug
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cIclops
post Mar 17 2005, 09:26 PM
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A simple solution would be to include a small device that could turn the rock over and image the date printed underneath.

smile.gif


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DEChengst
post Mar 17 2005, 09:34 PM
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QUOTE (cIclops @ Mar 17 2005, 09:26 PM)
A simple solution would be to include a small device that could turn the rock over and image the date printed underneath.

smile.gif

To do that we first would need to find some kind of Rosetta stone to learn Martian.


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cIclops
post Mar 17 2005, 09:54 PM
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QUOTE (DEChengst @ Mar 17 2005, 09:34 PM)
To do that we first would need to find some kind of  Rosetta stone to learn Martian.

A Mars bar code reader perhaps?


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Guest_BruceMoomaw_*
post Mar 18 2005, 03:28 AM
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More seriously, there IS a lot of interest in trying to develop a system that could at least crudely age-date Mars rocks in-situ -- and, in fact, such an instrument (designed by Timothy Swindle) was the main instrument on the proposed "Urey" Mars Scout mission. The plans are to utilize either K-Ar dating or Rb-Sr dating, by grinding up a rock sample and then firing a laser beam at it to volatilize the argon and those trace metals (with their relatively low vaporization points) out of the rock for mass spectrometric analysis. (Indeed, Beagle 2 -- with its X-ray spectrometer to measure potassium and its main system of rock grinders, ovens and mass spectrometer to measure argon-40 -- would have made a crude attempt at such dating.)

Even an accuracy to within 200 or 300 million years would be extremely useful in answering a lot of the most important Mars questions -- and it would also be very useful on Venus and Mercury landers. (Indeed, the possible development of such an instrument was listed by the National Research Council back in 2001 as one of the most important missing items in the Mars exploration program as it was then designed.) But such a gadget will be heavy -- it was, as I say, the central instrument on the Urey lander -- and so, even if a fully successful design can be developed, flying it won't be that easy. I think it possible that such a device might be put on the second MSL, for instance -- but not until the first MSL and the other missions of the same period have given us a better overall idea of just what instruments SHOULD be put on such later Mars rovers.
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