September 5, 2006
Mission: Returning a Soil Sample from Mars
NASA - At the recent Viking thirtieth anniversary celebration, Noel Hinners championed what could be the next great challenge for planetary science: a Mars Sample Return mission. Hinners pointed out that, like Viking, Mars Sample Return will prove to be extremely difficult but immeasurably rewarding.
For a Mars Sample Return mission, a rover would collect samples of rocks, soils, and the atmosphere, and then a rocket would blast off the surface of Mars and carry the samples to Earth for detailed analysis. While some people are opposed to bringing samples of Mars to Earth, the truth is that martian rocks are already here. To date, 34 martian meteorites have been collected from various sites all over the world. These rocks traveled to Earth after having been blasted off the surface of Mars by a comet or asteroid impact.Even though scientists can study these meteorites to learn more about Mars, the rocks have been altered because they went through a lot to get here "“- the explosion that first sent them flying off the martian surface, the cold, radiation, and vacuum of space, and then the fiery descent through Earth's atmosphere.
As Hinners explains in this edited transcript, a Mars Sample Return mission could provide generations of researchers with a variety of more pristine and scientifically interesting samples to study.
"One of the big challenges facing NASA today is Mars Sample Return. Mars Sample Return has been on the agenda for a long time, well before the late 60s, even before the Viking orbiter and lander. Like Viking, Mars Sample Return is a daunting technological and engineering challenge with an incredible scientific payoff. So what did we learn from Viking that might help us figure out how, within our lifetimes, to do Mars Sample Return?
Viking was viewed as incredibly challenging and complex, both for the technical and the science aspects. Looking for life is not an easy thing to do. There are many arguments about how to detect life when you don't know what that life is like. You have so many assumptions and analogies with terrestrial life as we know it.
Before Viking, the martian atmosphere was poorly known, the surface was poorly known, and the surface environment was poorly known. Some people viewed this whole endeavor as verging on insanity.
One effect of the probable Viking detection of "no life", if you call that a detection, was that it slowed down the exploration of Mars for several decades. Soon after Viking, I went to the Soviet Union, which also had a very vigorous Mars program, and I asked them about their next Mars missions. They said, "There aren't any." I asked why not, and they said, "You've killed them off. You didn't find life." So this quest for life has an incredible influence in the Mars program. Now there's been a revival of the potential for life on Mars, with the recent MER findings of the ancient presence of pervasive water.
The science imperative for Mars Sample Return is equally compelling to what Viking was looking for, and in many ways associated with some of the same goals related to life.
Impediments to doing Mars Sample Return have been technical and, in large part, budgetary. There's a lot of critical science that simply can not be done in situ. We're getting much better with our instrumentation to send to Mars, but we still cannot do certain things. The MER mission discovered what are called blueberries, these little round ball bearing-sized, millimeter-sized things. It would be wonderful to have those back here, in blueberry crumb cake. To dissect them, to see the layering in them, to do the isotopic study as a function of depth to understand the history of the water interaction with these materials, to look at the mineral phases and understand how they formed.
For something like the Mars meteorite ALH 84001, it can be looked at on the atomic scale here. You simply cannot manipulate and do the analysis on samples remotely with any of today's technology, or with anything we can see coming down in the near future. In the Stardust grains that came back recently, a zircon was found. This was at the micron scale, showing a high temperature mineral which isn't supposed to exist in comets. Remote sensing had never shown this before, and it has changed the way we think about where comets are coming from. What part of the origin of the solar system do they relate to? Is this a remnant of some previous generation of a star which exploded and ejected material into the solar system during its formation? More recently, in another Mars meteorite, there are little channels that it's very tempting to think may be what are called DNA tunnels. Probably not likely, but nevertheless it's at this scale where we see what is really going on.
Essential to Mars human exploration is understanding the chemically active material. Dust is always a problem. Unless you have inorganic lungs, I would not want to breathe Mars surface material. But if we get material back here, we could alleviate health and safety issues by figuring out what are the essential problems with the dust-sized particles on Mars.
When we have a human mission to Mars, we've got to know what it is we want to do for that kind of investment. Much of what they do there will be science. The science goals can be better defined when we know and understand what they're going to deal with when they get there.
We also need to show a sense of direction to the public. The public in large part does not comprehend why we are going to the moon and not to Mars. So I suggest that having some focus of our human program directed towards Mars at this stage would help to bridge that, and relate to why we're doing some things on the moon first to prepare for this eventual expedition, and maybe long-term colonization of Mars.
Samples are forever. We're still analyzing Apollo samples thirty years later. There are new techniques that did not exist when Apollo flew. So as instrumentation develops, you apply it to samples you've brought back. The Soviet LUNA missions brought back moon samples robotically in the early 1970s. The Soviets came close to scooping Apollo, in a sense. They had a sample return mission going to the moon at the same time as Apollo 11, but it failed. Politically that was good for us, although we don't like to see anybody fail in missions.
Competition played a role at the time of the Viking program. Prior to Viking, there were only four successes out of the six U.S. Mars missions: Mariner 4, 6, 7 and 9. Part of the support for Viking which made it "affordable" and sustainable was that we were in the space race with the Soviet Union, which had a vigorous Mars program. Today, we don't have that competition, although some people are trying to drum up the Chinese as a competitor to worry about today.
But I think we are now in an era of cooperation. We should cooperate on Mars Sample Return -- it will cost a lot to do it, so if we could bring in partners who could shoulder a significant part of the science and technology engineering and budget, that helps us get this mission into the U.S. space science budget. It also could provide a model for international cooperation. We have failed gloriously with our cooperation on shuttle and Space Station. We have tended to design a mission, find out that we can't afford it, and then go hat in hand to our friends and say, "Please come help us; we'd really like you to join us." There's nothing wrong with wanting their money, but let's bring them in early.
The European Space Agency is very interested in Mars Sample Return. In fact, their Aurora human spaceflight program has Mars Sample Return as a key component. It's only in a study phase at this point, but the interest is there, so the potential for having them as a partner is there, along with other countries. Other countries are showing that they can now accomplish many things which we used to think only we could do. ESA has Mars Express, and the Japanese recently did land on an asteroid. Although they had some problems, we think maybe they're bringing samples back. The capability is all over the world now. I say, let's bring them in early during the conceptual stage, and make them true partners.
The Viking heritage story is telling. In all the systems and subsystems, there was mostly new technology. Some technology existed but wasn't used, like solar arrays, because we didn't think solar arrays would survive the dust problem on Mars. So instead we used RTGs that had to be adapted for the Mars environment. All the new technology, for the most part, worked.
The lesson learned is that new technology is not something to be afraid of; new technology is to be embraced. You test the bejeebers out of it, and do everything you can to understand it. One of the most frightening things in our business is heritage technology, which frequently is misapplied. So let's bring on the new technology for Mars Sample Return.
But a lot of the Mars Sample Return mission technology already exists. For a Mars Sample Return mission, you need to launch to Mars, cruise to Mars, get into Mars orbit, and get down to the surface. We've been there, done that! We just need to do it right some more times. What is new is sample acquisition, plus a Mars ascent vehicle "“ we've not yet developed something to get off the surface of Mars. We need to put a sample into Mars orbit, rendezvous with it, bring it back to Earth, and do an Earth entry. And the equivalent entry, descent, and landing at Earth has been demonstrated by the Stardust comet sample return, so there's not a lot of new technology needed for that.
Viking today would cost 3.4 billion dollars. Mars Sample Return estimates run from 2 to 4 billion. Can it be that Mars Sample Return could cost less than Viking? At first, it doesn't make sense. But we have already developed many of the elements we'll need, so that the number of new things is much smaller than it was for the equivalent of Viking. If you did Viking today, my rough estimate is that using today's technology, a Viking mission would cost someplace between 1.5 and 2 billion dollars. So on a relative basis, the Mars Sample Return is more expensive than Viking.
I'd like to suggest that future lander missions need to start caching samples. When geologists go out in the field, you throw that first rock in your knapsack in the morning and you keep collecting all day. At the end of the day you may throw some out, but you've got your representative collection. For Mars Sample Return, getting the variety we see on Mars is important. And when you've got a mission like Mars Science Laboratory that may go for years on Mars and maybe travel hundreds of kilometers, we should collect samples so that we can eventually bring some of them back home.
Now, I wouldn't claim that Mars Sample Return will be easy. Like Viking, the devil is indeed in the details. Many people thought Viking was impossible, yet we did it. Let's now get on with Mars Sample Return. It will be equally challenging, equally achievable, and equally rewarding. "
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