Hydrated minerals map, MEx uncovers possible sites for life Options

[Guest_BruceMoomaw_*]

Actually, we've had a thread on this earlier ("Rock dating experiments" over in the "MSL 09" section). It won't have an instrument explicitly for that purpose -- but I now think it might be able to test the feasibility of K-Ar dating indirectly. You'll recall that there was going to be an attempt to do this on Beagle 2, by using its X-ray spectrometer to measure K in the local rocks while its main GCMS package roasted rock samples and analyzed the gases released, which would have included Ar-40. Well, I believe MSL's experiments will have the same capability -- it has two separate experiments capable of measuring K, and I believe its "SAM" GCMS package can, like Beagle's, measure Ar-40 from ground-up and roasted rock samples. It's probably worth my time to look into this.

There are at least two teams working on explicit Mars age-dating instruments that would use various techniques --
http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1492.pdf
http://www.lpi.usra.edu/meetings/robomars/pdf/6165.pdf
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1843.pdf
-- and Swindle's instrument would have been the main experiment on the "Urey" Mars Scout proposal:
http://trs-new.jpl.nasa.gov/dspace/bitstre...3/1/02-3063.pdf . Moreover, it seems to me that MSL's separate instruments do combine all the capabilities of the different components of the Urey age-dating experiment -- which would have tried to do not only K-Ar but cosmic-ray exposure age-dating.

It's also a fact that, a few years ago, COMPLEX listed this as one of the most important areas being neglected by the US Mars program as it was then designed. A few weeks ago, going through the Web documents on the question of how secondary craters may interfere with crater-count age estimates, I ran across one such abstract that recommended rough in-situ age-dating in 2 or 3 places on Mars' surface to settle the dispute.

[dvandorn]

Why, that's just fascinating, Bruce -- especially since, to my own question about this (likely in the thread to which you refer), I was rather loftily informed that the sample handling and preparation requirements for *every* existing rock dating technique require a delicacy of manipulation that unmanned probes would simple never achieve.

What changed?

-the other Doug

[Guest_BruceMoomaw_*]

Well, here's my one entry (March 18, 2005) on that subject in that thread. ((You didn't have any entries on that thread; if I made a comment on the subject anywhere else, I don't remember.)

"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."

I don't know whether that's "lofty", but it's certainly true that when I wrote it I wasn't putting in nearly enough thought on what the instruments on the first MSL -- not designed for age-dating though they are -- might nevertheless be able to do. As far as I can tell from looking at the design for the Swindle team's proposed "AGE" (Argon Geochemistry Experiment), every function it has will be duplicated by some part of the existing payload on MSL-1. (You'll notice also that I misdescribed Swindle's particular instrument; it would measure the argon just by grinding up the rock and roasting it in a GCMS oven, and the potassium using an internal LIBS spectrometer -- for which the three separate element-analyzing instruments on MSL-1 may be a fully adequate substitute. It's the other proposed Mars age-dating instrument -- designed by a U. of Hawaii team, and doing Rb-Sr age-dating -- that uses a laser to boil those two volatile elements out of rock samples.) They may not have the same level of measurement accuracy as the components of AGE, though. This is definitely worth our looking into. At a minimum, the first MSL may be able to give us a better idea of just how feasible in-situ age-dating on Mars actually is.

[dvandorn]

It was definitely in another thread, then. I recall asking about the feasibility of doing any actual rock dating in situ, and got told that all of the current dating techniques require extremely meticulous handling that just can't be done robotically. I recall expressing doubt about that conclusion, but was assured that we were a long away from such a feat...

I'm *very* glad to see that there are people who are thinking outside the box and coming up with inventive ways of dating rocks in situ. Let's hope these analyzers are available and sitting on Mars sometime relatively soon (like, say, within my lifetime... )

-the other Doug

[Guest_BruceMoomaw_*]

Once again, we're talking about really fuzzy dating -- with an accuracy level of only about 10-20% -- but, as the papers on the subject point out, even that could be extremely valuable in understanding just what the general course of geologial evolution of a planet has been.

[RNeuhaus]

In situ dating rock age measure would be a great improvement since up to know, the only way is to return the sample to Earth to be able to date the rock's age.

Rodolfo