12 June 2012
Yesterday NASA hosted a call-in press conference for reporters to announce some good news and some bad news about Curiosity. The good news: the landing system is going to be even more precise than expected. The bad news: the drill sheds teflon that gets into the samples.
I don’t know very much about the drill issue, but as far as I understand it, it should not significantly hamper the science measurements from CheMin and SAM. The drill and the sample handling system on MSL are so complex that it borders on the absurd, and the engineers at JPL are hard at work to understand the problem and tell us exactly what we can do to mitigate it.
The landing site is something I know a thing or two about, so I’ll discuss it in more detail. As you can see in the image above, the new ellipse (the darker one) is much smaller, and that means it can be placed closer to the base of Aeolis Mons (aka Mt. Sharp, aka the mound). A “landing ellipse” is the area on the surface where engineers are 99% confident that we’ll end up. The center point is the most likely and the edges of the ellipse are least likely. Now that the spacecraft is on its way, the engineers know its trajectory better than they did before, and by feeding that into their simulations of the landing, they were able to shrink the ellipse.
As you can see, the new ellipse is centered right on the edge of the mysterious material that has been dubbed the “high thermal inertia unit”. This unit is probably the top science priority within the ellipse: nobody knows why it has such a high thermal inertia (a property that indicates that it is a hard, solid rock as opposed to loose sand) but chances are it is cemented thanks to interaction with water. My gut says that it is the lower portion of the alluvial fan from the rim, but others think that it might be lake or playa deposits that were buried by the fan.
It’s awesome that we are able to land closer to the mound because in the end, the layers exposed there are the real science goal of the mission. We want to step through the pages of martian history by working our way up the stratigraphy of the mound. But at the same time, odd as it sounds, I’m worried that we will land too close to the mound and we won’t get the chance to study the high thermal inertia unit. It would be disappointing not to find out what cemented it, since that would provide a clue to more recent water activity on Mars (the fan and the channels in the crater rim are thought to be young relative to the base of the mound). There are also a lot of people on the team who are hoping that the alluvial fan will contain intact blocks of material from the very ancient crater rim.
So the big question is, what happens if Curiosity lands on the crater floor between the high TI unit and the mound? Do we take a detour to check out the high TI unit, or do we miss out on the high TI unit to get to the mound earlier? That would be a difficult decision for the team to make right off the bat, and I suspect that tempers might flare and feelings might be hurt no matter what the decision.
In the end though, we didn’t go to Gale for the ellipse science, we went for the mound. Anything that gets our rover closer to its primary goal is a good thing. On MER, once the rovers passed their 90 day life span, the team proceeded with a so-called “sniper mentality”. That is: the rover could die at any moment, so what should we do to get the most out of the mission? I’m sure this sentiment will be in full force for MSL too, and the new ellipse placement will save us months of driving, which is a very good thing.