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Mark Adler
Mark Adler
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The cost in the context of NASA's planetary budget is daunting. Furthermore the ability to estimate the cost of such an endeavor in the face of all of the significant technical challenges is limited. There is justified concern over the magnitude of the cost risk, even if initially the cost is considered to be palatable. That is where the deficit in confidence comes in. Not so much about a lack of confidence in it working — we always have to accept some risk there, butand we know how to mitigate it —— but rather a lack of confidence in our ability to limit budget and schedule overruns to a reasonable level for such an unprecedented technical undertaking. (See the James Webb Space Telescope.)

The cost in the context of NASA's planetary budget is daunting. Furthermore the ability to estimate the cost of such an endeavor in the face of all of the significant technical challenges is limited. There is justified concern over the magnitude of the cost risk, even if initially the cost is considered to be palatable. That is where the deficit in confidence comes in. Not so much about a lack of confidence in it working — we always have to accept some risk there, but we know how to mitigate it — but rather a lack of confidence in our ability to limit budget and schedule overruns to a reasonable level for such an unprecedented technical undertaking. (See the James Webb Space Telescope.)

The cost in the context of NASA's planetary budget is daunting. Furthermore the ability to estimate the cost of such an endeavor in the face of all of the significant technical challenges is limited. There is justified concern over the magnitude of the cost risk, even if initially the cost is considered to be palatable. That is where the deficit in confidence comes in. Not so much about a lack of confidence in it working — we always have to accept some risk there, and we know how to mitigate it — but rather a lack of confidence in our ability to limit budget and schedule overruns to a reasonable level for such an unprecedented technical undertaking. (See the James Webb Space Telescope.)

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Mark Adler
Mark Adler
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Money. Commitment. Confidence. Insufficient amounts of those three are why we haven't yet returned samples from Mars.

There is certainly motivation. The last planetary science decadal survey, Visions and Voyages, where the science community gets together and decides on priorities, rated as its number one flagship mission priority the first of three missions to accomplish Mars Sample Return, where that mission is now referred to as Mars 2020. It has the job of carefully selecting and collecting rock cores and other samples of the Martian surface over about three years, for eventual return to Earth later in the decade. ("Return" is probably the wrong word here — unless we picked the wrong samples, they certainly didn't come from Earth — but anyway "return" is the word everyone uses after "Mars sample".)

Even if NASA commits to the Mars 2020 mission (which could be in the near future), NASA will not be committing at that time to the two subsequent missions that would be needed to transport the collected samples to Earth. The Mars 2020 mission was conceived to have a very robust and novel in situ investigation capability that would justify the mission even if the samples are never picked up.

If the subsequent missions go forward, one of them would be a lander with a fetch rover to go get the retrieved samples and a Mars ascent vehicle (a rocket) to launch the fetched samples into a low Mars orbit. The other mission would be a Mars orbiter that rendezvous with and captures the orbiting sample container and then departs Mars orbit, returns to Earth (there "return" works), and as currently conceived send the samples down to the surface of the Earth in a small entry vehicle. Each of those missions are of the flagship class, which would dominate the planetary science budget for a decade or more.

The cost in the context of NASA's planetary budget is daunting. Furthermore the ability to estimate the cost of such an endeavor in the face of all of the significant technical challenges is limited. There is justified concern over the magnitude of the cost risk, even if initially the cost is considered to be palatable. That is where the deficit in confidence comes in. Not so much about a lack of confidence in it working — we always have to accept some risk there, but we know how to mitigate it — but rather a lack of confidence in our ability to limit budget and schedule overruns to a reasonable level for such an unprecedented technical undertaking. (See the James Webb Space Telescope.)

International partnerships could mitigate the cost, but two attempts at that around the late 1990's and late 2000's both were eventually abandoned. Maybe we're due to try to kick that football again.

The cost and the cost risk, plus the very long time scale of investments over more than a decade with limited payoff unless and until it is successful at the very end of the campaign (longer than any administration), has led to a lack of commitment to Mars Sample Return in the leadership of the US government, including the White House and the Office of Management and Budget.

It would be the dominant fraction of the total planetary budget over more than a decade, where even that fraction might not be enough, so it is difficult for a government that works on year-by-year funding uncertainty to commit to something like that where the payoff doesn't come until the end. Still there is hope that this might get pulled off someday, one mission at a time. Once we have samples on the surface ready to be picked up, we have more motivation ahead of us and more cost behind us.

As for the technology, there is time to develop what's needed even if there were a commitment today to develop and launch all three missions in a serial fashion, picking up on the next mission as the funding wedge on the previous one starts to drop. Nothing about the mission is insurmountable. The greatest challenges are in the area of planetary protection, which impact every phase of the mission from sample collection to Earth entry. Some of those planetary protection challenges are being tackled by the Mars 2020 mission already, as is the significant challenge of collecting intact rock cores. The orbital rendezvous and capture and the Mars ascent vehicle are engineering challenges, not new technology. Overall, there is a ton of work to do, but there are no apparent showstoppers so long as there is flexibility in requirements. This can happen, but only if there is a serious commitment and money to go along with it.