One of the important aspects of terrestrial analogs is a potential of using scientifically relevant field sites as the test sites for newly developed instruments for future space missions. Kris will help us start up discussion on advantages and problems of using a great terrestrial analog as a field-testing site.
The discussion starting points are:
1. Which specific Mars conditions are particularly important for testing of instruments and sample acquisition and handling devices, and why?
2. What conditions are easier to simulate in terrestrial analogs (as opposed to laboratories or vacuum chambers), and why?
3. Which analog sites have good logistic support that would be suitable for field-testing?
I'll start off with a response to Kris's first question. For most instruments, if you're talking about testing it's mostly about getting the temperature and atmospheric density right. When we were testing the payloads for MER, the most valuable tests were the ones performed in thermal vac chambers, not in the field.
For sample acquisition and handling, it's a little different. There you also have to include issues like the physical/mechanical properties of the materials involved. So you're talking about dealing with rocks, dirt, outcrops, etc. Temperatures are still crucial, and there's no substitute for testing in Mars environtmental chambers. But I think that a better case can be made for doing some tests of flight-like sample acquisition/handling hardware in a field setting than can be made for most instruments, because it's hard to do dirt and rocks and outcrops in a thermal vac chamber.
Steve, the need for outdoor analog sites is defensible with the same logic that lunar analog sites have proven useful. While you can not replicate atmosphere and gravity in such sites, environmental chambers have trouble replicating the vagaries that plague low TRL systems. If this analysis is reasonable, then it suggests that picking an analog is driven not so much by the science questions as by the mechanical systems to be tested at low TRL levels. I offer this as a possible frame of reference simply because the cost of mobilizing to many potential analog sites is quite high. While interesting and a source of great pictures, the engineering benefits may not be worth the cost.
If a remote analog site is felt to be essential, the superior benefit to the program should be clearly demonstrable. This is a burden advocates for a site or any site must bear. Which gets back to Kris’s excellent questions.
Yeah, I don't disagree with anything you've said. In fact, for instrumentation I would argue that the lower the TRL, the more it makes sense to go out into the field with it. If your hardware is truly flight-like, you probably neither need nor want to take it into a field setting. But for low-TRL stuff, where you're just trying to get a feel for what works and what doesn't, getting hardware out into a field setting can be a very educational experience!
I think a “good field site” also depends on what you are indenting to do. For example, if you have an instrument that looks for certain compounds then it would be very useful to use a terrestrial analog that is most similar to the one on Mars, containing that particular compound. And that could be a different site for different things to be detected.
As someone who was recently added to the MSL team, and is a total rookie in terms of mission participation, I've been fascinated (overwhelmed!?) by the high-paced nature of mission ops discussions. In particular, I've been impressed with the ability of people to balance speed and rigor when going from data downlink to interpretation, and then to future mission planning.
I've been similarly impressed with the forethought given to how multiple measurements can give a more complete picture of a sample/site.
Again, I'm a complete rookie in this area. (Usually I sit at the safety of my desk and run model simulations for weeks or months before forming an opinion on something.) But I wonder if there are challenges here that can be simulated on Earth, w.r.t. specific instruments or suites of instruments. If so, are there sites more appropriate to this sort of thing, based on their mineralogical/chemical/morphological characteristics? Or are these challenges the same across sites?
It's indeed very useful to conduct field simulations where you go out to an analog site and conduct a simulation of flight operations. This was done extensively prior to both MER and MSL, and its primary value was in science team training. You can run simulations in indoor or outdoor "Mars yard" settings, but these don't really train a science team to do the kind of things you're talking about. There's no substitute for going somewhere that has real scientific problems to be solved. A lot of the team proficiency you're talking about was first developed in these field simulations.
It's worth noting that you don't necessarily have to actually have a rover that you can take into the field to do this. It just has to >look< to the science team like there's a rover involved. You can often accomplish the same thing using things like tripod-mounted cameras and laboratory analytical instruments that mimic what you'd have on a rover. The really important thing is that the analog site should mimic as closely as possible the kinds of scientific puzzles you expect to have to deal with on Mars.
If the simulation of working at the outcrops and with surface dirt is unique for fied-testings; what type of logistic support would be the most important during the field operations?
In my experience, the kinds of logistical problems that cause the most trouble are often ones associated with hardware failures, especially when you're working with the kind of low-TRL stuff that most benefits from being taken into a field setting. It goes without saying that you always want to have a lot of spare parts, a lot of tools, and people who know how to use them. But there are always going to be failures you can't anticipate. So sometimes it's valuable to pick a field site that is not as "remote" as you might like it to be. It doesn't matter how Mars-like your field setting looks, if the only way to get your data is for somebody to Fedex you a part you don't have, you don't want to be too far from home. Very exotic field sites can have a lot of appeal, but I'm an advocate for testing as close to home as you can if the results you'll get there are good enough. (A classic example of the old engineering adage "better is the enemy of good enough".)
Back in 2010 we did 1 m drill tests in ice cemented ground and in massive ice in University Valley, Antarctica. The air T was <-10 C, air was dry, and ground/ice was at -20C. The sample capture system was in a shadow of the drill deck. I noticed that drill cuttings did not stick - they behaved almost like dry sand. In our Mars chamber tests on the other hand, cuttings would stick (the ambient air in the chamber was ~+20C). This taught us a very important lesson about sample acquisition in ice and icy-soils: keep it cold and away from direct sunlight. We might have noticed a similar behavior if our chamber had LN2 jacket to reduce atmospheric temperature. But of course in the field, it's much easier to observe such behaviors than trying to look through a chamber window or a chamber camera. In addition, it would had been quite expensive and time consuming to cool down a 4m^3 volume to <<0C for each test.
Kris, was the humidity in your chamber controlled? Do you think that maybe it was relative humidity that was responsible for the behavior of the cuttings in the chamber, rather than temperature?
We can't control RH very well except for continuously flushing with dry N2 and running vac pumps (this helps a little bit). Mars Phoenix soil, however, was sticky and dumping the soil out of the scoop was difficult. I believe the scoop was exposed to sunlight and hence I believe this had something to do with it.
I think the conditions that are easier to simulate in terrestrial analogs are those within subsurface. Because the environment there would be controlled mainly by surrounding materials (e.g., hydrous salts), but less influence by surface atmospheric conditions which are quite differ between Mars and terrestrial analog sites (even those sites at polar regions and on high plateaus).
We know very little about Mars subsurface -- rovers and landers dug into tens' cm, while models predict the change of conditions in deeper depth and simulating experiments suggest very different mineralogy there (thus environment for potential habitability). Therefore the question to next mission is how deep we can dig into and if we can conduct immediate check of materials ? Which are related to technical capabilities and Mission budget......,
For that reason, we can dig into the subsurface in a terrestrial analog site, and do a lots ... :-)
I agree with Steve that one the greatest value of testing instruments in the field on real samples with real science questions attached to them is that you really start thinking about the questions you want to answers on Mars and what information and technology you need to answer these questions. In this respect testing on an analogue sample in a lab is not really the same as testing on the same sample in the field.