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tedstryk
Has anyone heard any update on the possibility of two MSLs?
DEChengst
Yep. That's under study at the moment and it should be decided to do it or not in a few months time
tedstryk
I was hoping that Bruce, since he has been at the roadmap meeting, might have gotten some word as to which way things seem to be leaning.
BruceMoomaw
I can tell you that the Roadmap Committee was very enthusiastic about the idea -- in fact, judging from this first meeting, it will be one of the strongest recommendations they'll make, for two reasons. First, MSL is an expensive vehicle, and utilizing it more than once -- if it's at all scientifically worthwhile to do so -- would be cost-effective.

Second, it IS scientifically worthwhile to fly it more than once -- because it is yet another advance reconaissance vehicle for more sophisticated later landers. Its primary purposes is, first, to understand Martian mineralogy -- and thus the planet's geological and climate history -- in absolutely unprecedented detail (the MERs succeeded beautifully at their goal of determining whether there have been significant amounts of liquid water on at least some of ancient Mars' surface at some times, but their mineralogical instrumentation is extremely limited). Second, it is intended to look for places on Mars with significant traces of complex organic compounds which might perhaps be biological remains. In that latter respect in particular, it will try to determine a promising landing site for either the later Mars Sample Return or the "Astrobiological Field Lab", a later MSL-like rover which would examine the nature of any organics found by MSL in vastly greater detail to determine whether they really are likely to be biological rather than non-biological in origin. If MSL finds organics, either mission is likely to make its first landing at the same site as MSL. But if it does NOT find them, we will be largely in the dark as to where to send either MSR or AFL. So the logical course of action is to fly one or two more MSLs -- either before the more sophisticated missions, or interleaved with them -- to find the best possible landing sites for those extremely expensive and infrequent later missions (especially sample-return missions, whose estimated cost is now back up to fully $3-4 billion for just 2 pounds of samples, and whose sample-collecting mobility will be limited to a few thousand feet around the lander).
tedstryk
Thanks. I really hope they go with two. It seems risky enough a mission that two rovers would be wise. Also, consider the MER mission. Imagine if Spirit flew alone, and landed a bit farther from the hills. The mission would have lost a lot of its major discoveries. I realise MSL will have precision landing, but you can be very wrong about a site from orbit. I would also wonder if Phoenix might, in a twist of fate, end up being the site for AFL. Seems that if there are organics on Mars, digging would be the best way to find them. On a side note, I wonder how long the MSL (s?) will last. I mean, look at Viking 1, and it was only turned off by a controller accidentally. This will be a really exciting mission.
BruceMoomaw
Two more notes:

(1) It is indeed possible that we will end up going down rather than sideways to look for Martian organics. If none of two or three MSLs turned them up in promising sites, the next step would probably be another possible future Mars lander: "Deep Drill", which is basically just a stationary version of Astrobiology Field Lab that would drill down 10 to 20 meters.

(2) Consideration is again being given to an idea that was popular before but then dropped for a while: combining an MSL with a sample-return mission. The tentative plans for a somewhat cheaper stationary "Groundbreaker" as the very first sample-return mission -- which would just scoop up samples from its immediate vicinity using a digging arm, providing great geological information but little chance of organics -- have now been dropped, thanks to the spectacular results from the MERs' mobility. But the plan that's now been revived still involves just a small rover (maybe even smaller than MER) collecting samples from a fraction of a kilometer around the lander and then returning them to it -- which still leaves a great risk that no organics or microfossils would turn up in its samples.

By contrast, one can conceive of an MSL driving dozens of km across the surface, doing detailed in-situ analyses of samples and saving a small subset of the most interesting ones -- and a sample-return lander later landing close to it, so that the MSL could hand over a really impressive (if still small) set of samples to it. Now, the earliest that a sample-return mission can possibly be launched (and this is starting to look optimistic) is 2013, which means there's a serious risk that the 2009 MSL would no longer be working by then. But later MSLs might be launched only 2 years before their associated MSR landers, making this scheme workable for them.
tedstryk
So from this I get that the MSL design, if successful, might become the "standard" Mars surface exploration vehicle for a few years. I still say the one thing that might throw a kink in this is if Phoenix finds something ultra-compelling under the surface. That would almost certainly change post-2009 plans in favor of drilling missions. That or if Spirit spots a camel treking across Gusev from Husband Hill.
BruceMoomaw
The Committee would very much like to make the core avionics of MSL the standard vehicle for as many future Mars landers as they can manage -- including the Sample Return landers. NASA's official plan is already to reuse the MSL lander module for all future Mars landers of similar size, including MSR -- which makes it doubly important to establish whether Skycrane is a viable concept.
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