Earth_Magazine_October_2017

exists on Earth in terrestrial laboratories

to answer that question, as well as many

other questions.”

ExoMars is not set up to cache samples,

but, rather, to figure out where the most

interesting and enlightening rocks might

be located for a future sample-return mis-

sion to retrieve, Vago says. “Mars sample

return is a complex mission; it’s an expensive mis-

sion,” he says, so it’s not guaranteed to happen often,

or at all, without broad support. What’s needed is a

“discovery to catalyze” that support, he says: “some-

thing that is so interesting that we would want to

return samples to Earth for analysis.” In trying to

find that key discovery, he says, ExoMars is a link

“in the chain toward Mars sample return.”

In addition to catalyzing interest, and funding,

for sample return and manned missions, numerous

technological hurdles must be overcome before

these goals are achieved. For instance, the means to

launch a spacecraft off the surface of Mars does not

yet exist. Carrying the tens of tons of fuel needed

for a return trip back to Earth — to return cached

samples or humans — would be hugely taxing for

a Mars-bound spacecraft, so the idea of remotely

producing fuel on Mars holds distinct appeal.

“MOXIE is really the big step forward” in this

regard, Farley says. Unlike SHERLOC and the other

main instrument payloads on NASA’s 2020 rover,

which are all largely motivated by scientific questions,

MOXIE (Mars OXygen In-situ resource utilization

Experiment) is a technology demonstration of a

system that generates oxygen from Mars’ carbon diox-

ide-rich atmosphere (see sidebar, page 37). This

oxygen, combined with methane most likely, could

serve as the main ingredient in rocket fuel; and further

down the line could provide breathing oxygen for

human explorers stationed on the planet.

MOXIE “is basically fuel-cell technology run

backward,” says Michael Hecht, a planetary scientist

at MIT’s Haystack Observatory and MOXIE princi-

pal investigator. In a typical fuel cell, oxygen would

be combined with fuel to produce electricity, with

carbon dioxide as a byproduct. With MOXIE, Hecht

says, “we start with carbon dioxide and energy [from

the rover’s power source], and we get out carbon

monoxide and oxygen.”

Hecht, along with many others, has closely fol-

lowed news of SpaceX’s Red Dragon mission, in part,

he says, because “it has something in common with

MOXIE in that it’s taking a very substantial tech-

nology step toward a human landing.” The company

has already demonstrated the use of powered descent

systems to land its Falcon 9 rockets back on Earth

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