Mars Sample Return Options

[Rakhir]

Next phase reached in definition of Mars Sample Return mission

http://www.esa.int/esaCP/SEMJAGNFGLE_index_0.html

[mcaplinger]

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.

[Mark Adler]

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.

[mcaplinger]

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.

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.

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.

[Mark Adler]

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.

I'm not sure you're taking into account the cost of the latest rover mission. Either that, or you have much larger estimates for MSR than I have seen.

In any case, I am not proposing that we drop all in situ missions and do MSR exclusively. The downside of MSR's is that you invest a great deal of resources in a very small number of sites on Mars. We need to continue the in situ missions in order to cover more sites on Mars, and help us better decide which of those sites are worthy of the MSR investments.

Folk here are wondering why we should even be talking about MSR, since there's obviously no way we'll ever be able to afford it, or if we can afford it, it would hijack the entire program at great risk with the potential of no return (so to speak).

I am not assuming no risk. I am assuming that there will be more than one MSR. If parts of the first attempt fail, then we learn and try again. That is the nature of this business. It is not for the faint of heart.

I am thinking on the 100-year time scale, considering what is the most effective way to explore Mars. In my mind, several sample returns from Mars, say on the order of ten, would be much, much more efficient than a pure orbital and in situ program. There are likely questions we wouldn't be able to answer definitively at all with only a century of in situ work. The life question comes to mind.

As for affordability, MSR can be spread out over multiple opportunities, and could and must coexist with other mission types for the reasons mentioned above. MSR objectives can be split into sampling, ascent, and return missions (requiring both a surface and an orbital rendezvous). That kind of split also has the benefit of spreading the risk, and allowing for more flexible program planning for the introduction of other missions as well as in situ and orbital objectives added to those MSR components.

Some argue that we do not yet know enough to decide where to send MSR. If we thought that there would only be one MSR, ever, for all eternity, then I'd agree. However many science groups have discussed this issue, and we certainly know several places today to send the first MSR, for which those samples would increase our knowledge of Mars manyfold. The results would further instruct the planning for future orbiter, in situ, and sample return missions.

I won't try to do the $ calculations here (since that's fraught with peril, and no one agrees on the numbers anyway). However I think that to first order, a scientifically-rich combined orbital, in-situ, sample return Mars program with about one sample returned per decade could be maintained for on the order of (fy08) $800M a year. Not all of that has to come from the US, and probably wouldn't.

The question of whether such a program would remain sufficiently important in the minds of world policy makers to justify that investment, I have no idea. But that's their job, not mine.

[Stephen]

If we thought that there would only be one MSR, ever, for all eternity, then I'd agree.

With all due respect, that may be exactly what will happen.

How many (unmanned) Lunar Sample Return missions has America ever launched? Once the Apollo program was lofted into political orbit courtesy of JFK there was no need to send any. The manned missions were expected to handle the sample returning part.

That particular precedent suggests that the window of opportunity for NASA MSRs will only last until manned missions to Mars find their way onto NASA's launching schedules (as opposed to the mere vague promise we have at the moment of having some manned missions to the Red Planet at some unspecified point down the track).

Moreover the window will probably close some years before the first manned mission is actually sent because those will be the years NASA will be wanting to give priority to sending unmanned missions which will support the manned ones. Sample returns will probably find themselves at the end of the queue unless they can be justified in a manned context. (Eg sending rovers on several years ahead to collect samples for the astronauts to retrieve. But that isn't quite the same thing as a fully unmanned MSR.)

For example, if NASA sends its first manned missions in the mid to late 2030s then even at a rate of one MSR per decade it's unlikely there will be more than 1 MSR because at some point in the mid to late 2020s, or early 2030s at the latest, the "window" will close as NASA begins ramping itself up for the manned missions. If the first goes by 2018 then by hurrying the second you might squeeze in two, especially if parts of the first (eg the rover) could be reused and/or if parts of the MSR (eg vehicle frames, Martian launch vehicles) could be standardised so that the proverbial wheel did not have to be reinvented for each mission, and also reducing the lead time. But sending the MSRs to the same part of Mars simply to cut costs and get a second in may not go down well.

And of course that is all assuming the first part of the the first MSR leaves in 2018. The longer the first gets delayed the less likely there will be many more. Or even any more.

Then there's the growing competition for a slice of the NASA funding pie from other high-priced unmanned missions in the decades to come, especially into the outer solar system. NASA is slowly accumulating a growing number of increasingly expensive committments--or at least expectations for--flagship missions to places like Titan and Europa. It seems fair to say that at least two contenders are already an inevitability: a Europan orbiter and a Titan/Enceladus mission; and one can foresee at least two more in the years beyond 2030: a mission to probe below the ice of Europa into its putative ocean (most seem to be expecting an Europan orbiter will confirm such an ocean) and a Neptune orbiter;and maybe a Titan rover/balloon also if the next Saturnian mission isn't such a one. Already NASA is having to pare back Mars funding to pay for its next outer planets flagship mission (which in turn may force the MSR to steal funds from other Mars missions like the AFL).

Unless NASA's overall funding improves that sort of thing is only likely to grow worse. What will probably happen is that some missions will get pushed back to pay for others. The problem MSR missions face is that if they get pushed back far enough sooner or later they will collide with any American manned program to Mars which does eventuate.

My own guesstimate is that if the first MSR does start in 2018, then the next is not likely until around the mid to late 2030s, with maybe a third some time in the early to mid 2050s. That is, 15-20 years between MSRs. Under that scenario, however, to have a second would require the manned missions be pushed back to the 2050s while a third MSR would only occur if manned missions were pushed all the way back to the 2060s or later, which frankly would be a tragedy. (In fact if it did happen one can almost predict the likely landing date of the first mission now: July 20, 2069!)
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Stephen

[AndyG]

...July 20, 2069!)

Much as I love robots, that is too depressing.

Will they take 106-year olds?

Andy