Mars Sample Return |
Mars Sample Return |
Apr 7 2006, 07:32 AM
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#1
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Member Group: Members Posts: 370 Joined: 12-September 05 From: France Member No.: 495 |
Next phase reached in definition of Mars Sample Return mission
http://www.esa.int/esaCP/SEMJAGNFGLE_index_0.html |
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Mar 29 2008, 10:17 PM
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#2
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
It seems to be a foregone conclusion among many that MSR is the next major goal for Mars exploration.
I'm confused by this for two reasons (neither new to this forum but worth reminding everyone of): 1) I haven't seen any objective evaluation of the cost of sample return versus the cost of in situ measurements. For some large class of measurements, in situ would be far cheaper. Presumably this was the motivation for the "Astrobiology Field Lab". Is there a "sample return mafia" pushing for samples? 2) Fear of the "Andromeda Strain" scenario (justified or not) will impose all kinds of sterilization requirements on the returned samples, making MSR even more expensive. I think MSR would be extremely cool, but I fear it won't happen for a long time. I also note that Stern was pushing MSR back in mid-07, which seems at odds with the perception that he was advocating fiscal responsibility. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Apr 9 2008, 12:58 AM
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#3
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Newbie Group: Members Posts: 17 Joined: 6-October 06 Member No.: 1230 |
1) I haven't seen any objective evaluation of the cost of sample return versus the cost of in situ measurements. For some large class of measurements, in situ would be far cheaper. Presumably this was the motivation for the "Astrobiology Field Lab". Is there a "sample return mafia" pushing for samples? Let's assume that all instruments can be brought to Mars, and that we can do the laboratory measurements as well there as here. (Obviously not the case for many measurements, but folk like to argue about those comparisons even though it's not all that relevant to what in my mind is the strong argument for sample returns, which follows.) Let's say we can do ten such measurement types per rover on multiple locally collected samples. To first order, we can figure that one such set of locally collected samples brought back to Earth will be the cost of, say, five rovers. Then if we want to do 50 such measurements, it's a wash. If we want to do 100 such different measurements, then the sample return is a win. (The Earth measurements will be so much cheaper than the mission, I neglect that cost here, but if you include that cost, the answer will be about the same.) I'd like to know how many different types of analyses were done on the Lunar samples after return. Just in the first three years. I'd wager it's in the thousands. Now let's look at schedule. This is the real kicker for me, since I'm impatient. Whenever we send an instrument somewhere, it answers some questions, and raises many more new questions. For Mars, we could respond to that with a new in situ instrument at best three opportunities, or 6.5 years later. It happens again, another 6.5 years. And so on. The pace of discovery can be excruciatingly slow, even if you're lucky enough to have something like a Mars Program that keeps sending things there. (I've been through a few of these cycles, and it can really wear you down.) However, if you have samples here, you do a measurement. It raises questions. You do a new experiment months or weeks later in your own lab or in your colleague's different lab with different equipment. You publish a paper and within a year other labs are answering more questions you raised. While you're waiting for the next Mars in situ mission to be developed and flown, our knowledge of Mars has been completely revolutionized by the equivalent of dozens of in situ missions. The cycle time of discovery is one to two orders of magnitude faster. So in my mind the strongest arguments for Mars sample return are simply cost and schedule. Sample return is much more cost effective and much more schedule efficient for extensive laboratory investigations than sending in situ instruments to Mars. Even if I completely set aside the issues of packaging entire Earth laboratories in a shoe box, and even if I completely set aside the continuing improvement in the capabilities of Earth laboratories and their application to already collected samples. |
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Apr 9 2008, 03:12 AM
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#4
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
I'd like to know how many different types of analyses were done on the Lunar samples after return. Just in the first three years. I'd wager it's in the thousands. I'd bet that there were less than a dozen critical measurements made (age dating and isotopic abundance stuff, primarily), and a whole bunch of essentially trivial and unimportant ones. But I'm not a geologist. QUOTE I've been through a few of these cycles, and it can really wear you down. I've been doing pretty much nothing but Mars stuff for twenty years, and I, perhaps more optimistically, view it as job security. QUOTE So in my mind the strongest arguments for Mars sample return are simply cost and schedule. I think you make a very good argument, but I think to really do the tradeoff you have to have a better idea of the kinds of measurements you want to make at a given time and how best to make them. It's often hard to sell big expenditures without knowing what you hope to learn more specifically. It would be more clear-cut if sample return could be done for the cost of, say, 3-4 rover missions, instead of the current estimates, which are in the tens at least. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Apr 10 2008, 06:43 AM
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#5
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
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Apr 10 2008, 08:24 PM
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#6
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Member Group: Members Posts: 384 Joined: 4-January 07 Member No.: 1555 |
There's obviously a trade-off. The rover (mobile) or in-situ (e.g., orbital or on-the-ground) lab approach yields lots of imprecise, necessarily ambiguous data from a handful of instruments for a large number of sites or samples. People here, including me, love that the rovers provide superb imaging (i.e., geological context) for each site. The MSR approach yields wonderful, incredibly precise, incredibly detailed geochemical, isotopic, microscopic, mineralogic, crystallographic, etc. data (independently confirmed at multiple laboratories) on a relatively small number of samples, whose geological context may be less well constrained. Given severely limited budgets, we have to choose. If we choose the MSR approach, we have to be super-careful about geological context.
My conceptual problem - I'm not sure that 20 rovers, imaging and crudely analyzing various occurrences of cross-bedded salty fines and spherules, would unambiguously tell us much more than we know now after imaging and analyzing such rocks at 2 sites (and, in the case of the respective MER teams, coming up with completely different interpretations). If each rover studied different rocks, that would obviously be ideal. That ideal is, however, difficult to achieve when engineering constraints restrict landing sites largely to equatorial flat areas, whose surfaces tend to be dominated by deposition/erosion via late impacts and the wind. Geologists long to study more challenging features such as "young gullies" formed only on steep slopes and the layering exposed in steep canyon or crater walls. Can the present generation of rovers, however long-lived, ever satisfy that longing? -- HDP Don |
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