A Faster, Leaner Mars Sample Return Isn’t the Good Idea It Appears to Be

In this case, savings don’t equal better science.

Artist's concept of Mars samples on their way to Earth.

Thomas Zurbuchen, the head of NASA’s science office, recently gave an update on the agency’s Mars program to a National Academy of Sciences committee that’s reviewing  progress toward implementing the Planetary Science Decadal Survey, a kind of wishlist of missions that scientists would like to see happen in the next 10 years.

One of the revelations from Zurbuchen’s talk is that NASA is now considering a “lean” version of its long-planned Mars Sample Return mission, which would send a spacecraft to collect Mars rocks for eventual return to Earth. According to the streamlined plan, no new Mars orbiter would be required for handling spacecraft communications if the mission launches from Earth by 2026 or so.

But what seems at first glance to be a good idea, especially to budget-conscious people, really is not. The current Mars orbiters are getting old, and a new orbiter such as NeMO is urgently needed, not just for sample return, but for future missions as well—especially if we hope to launch human expeditions to Mars in the 2030s. Such an undertaking requires more spacecraft in orbit around Mars, not fewer.

While the leaner mission would return “cached” Martian samples in just nine months, which is faster than in other scenarios, that’s still too long for detecting reactivity within Martian soils. The results of the Viking life detection experiments of the 1970s are still ambiguous to this day; we only know that after several months in a box, possible biological activity observed in the samples was not observed anymore. We appear not to have learned from Viking. And launching a “lean” version of this mission would seriously limit the amount of science any rock-collecting robot could do on the surface.

Why do we want a Mars Sample Return mission in the first place? The greatest advantage of returning samples would be to determine the absolute ages of Martian rocks, which geologists would really like, (and, as a geoscientist by training, I understand). But would the soil, boxed up for nine months on Mars, then shipped on a slow spacecraft back to Earth, provide the scientific insights we really need for human exploration? When I attended the first human landing site workshop in 2015, NASA’s mantra for Mars was that every mission beyond 2020 had to support the future human missions. This is clearly not the case with a lean version of a Mars Sample Return mission. 

Instead, we should be contemplating a mission to examine the Martian soil while still on the surface, perhaps combined with a life detection experiment. That way we could evaluate whether the Martian soil poses a danger to future astronauts. And such a mission would not trigger planetary protection concerns about bringing contaminated samples back to Earth.

It may sound counter-intuitive, but the idea of a cheaper, faster, “lean” Mars Sample Return mission should end up in the trash bin, along with other past mission concepts, some of which were much more deserving than this idea.

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