By Eric Hand
ARLINGTON, VIRGINIA—In the sea of planetary scientists here last week for the first Mars 2020 rover landing site workshop, the engineer stood out. He was decked out in his cus- tomary rockabilly regalia: earrings,
pompadour, and blue jeans cuffed meticulously above ankle-length black boots. But
his nametag was spare. It just read “Adam.”
“First name only?” chuckled Al Chen, another engineer at the Jet Propulsion Laboratory (JPL) in Pasadena, California.
Around these parts, Adam—JPL engineer
Adam Steltzner—needs no introduction.
He led the development of the jet-powered
Steltzner’s issues begin with the drilling.
“sky crane” that unspooled NASA’s Curios-
ity rover to the surface of Mars with un-
precedented precision in 2012. Now, NASA
is planning its next rover, a $1.5 billion ma-
chine to be launched in 2020. Steltzner’s
sky crane will be enlisted again. But NASA
has called on Steltzner to stage a differ-
ent engineering tour de force: gathering
a trove of rock and soil samples that will
ultimately be returned to Earth, to be in-
spected for clues to martian geology and
signs of ancient life. “It’s no accident that
Adam is on this,” Chen says. “We’re bring-
ing the A game.”
Scientists want the rover to drill at least
31 rock samples weighing about 15 grams
apiece during its 2-year mission and pack
them in a honeycomblike repository that
a later mission will retrieve. It will have to
work faster than the current rover, Curiosity,
which has drilled just three samples in its
20 months on Mars. To make the next rover’s
job easier, the nearly 100 planetary scientists
at the workshop focused on potential land-
ing sites that pack maximum geologic diver-
sity into relatively small areas (http://scim.
ag/Mars2020). Mission planners are also
planning to limit the rover’s other scientific
tasks, keeping it nimble so it can reach as
much of that diversity as possible.
On Earth, drills are lubricated and kept
cool with water, which also flushes out
the detritus. On Mars, Steltzner is limited
to rotary-percussive drilling, which works
without water but carries risks. Laboratory
scientists need cohesive, uncontaminated
rock samples—but how do you hammer and
destroy the material around a sample the
size of a stick of chalk without fracturing
the thing you want? Temperatures also have
to be controlled: If they rise too high, they
could alter the hoped-for organic molecules
inside the rocks.
Designing the sealed tubes in which
samples will await return poses another
challenge. Make them out of stainless
steel—a strong, ductile material—and you
risk contamination from reactions with
the metal. Make them out of an inert material like sapphire—perfect for avoiding
contamination—and they could be too brittle for a bumpy ride back to Earth.
Above all, Steltzner needs the rover
to work quickly. To make more time for
sample selection, Steltzner says, engineers
might create an onboard “parking lot” for
samples so that scientists could evaluate
them while the rover is on the go—before
committing them to one of the precious
caching spots. They might also design the
cache—the chamber that holds the sample
tubes—so that samples can be ejected, or
even provide multiple caches so that scientists can change their minds about which
rocks to send home.
Mission planners are also trying to limit
the rover’s capabilities. A science definition team report, released last July, recommended a $100 million instrument payload
that would make brisk measurements.
Time-consuming experiments like Curiosity’s CheMin—the first x-ray diffraction in-
NASA planners gear up
Engineers and scientists designing the Mars 2020 rover
for martian sample return
keep an eye on geologic diversity—and the clock
Scientists hope a future
mission will ferry Mars
rocks back to Earth.