Q&A
JANUARY/FEBRUARY 2020. DISCOVER 49Talking to a
Tw i n T r a v e l e r
BY JAKE PARKSi
Every grade-school scientist
knows a good experiment needs
a control — a test subject you
leave alone to have a baseline
for comparison. So when NASA
researchers set out to learn exactly how
weightlessness and other space hazards
like radiation might change the human
body, they needed someone to stay behind
on Earth as a counterpart. The ideal con-
trol would be someone very similar to the
space traveler, so NASA chose an actual
clone — or, as they’re more commonly
known, an identical twin.
Thus was born NASA’s Twins Study.
From 2015 to 2016, astronaut Scott Kelly
spent a year aboard the International
Space Station. Meanwhile, retired astro-
naut Mark Kelly — Scott’s twin brother
— stayed on Earth. The results, published
in April in Science, show spaceflight
indeed triggers changes in the human
body, such as damaging DNA, thickening
artery walls, modifying the microbiome
and altering gene expression. But the
vast majority of these changes disappear
within a few months of returning to Earth.
Through the Twins Study, researchers
now have a better understanding of the
hazards of spaceflight and can work on
how to deal with them. The results may
eventually help us venture to the moon,
Mars and beyond. We spoke with Scott
Kelly about the findings, the possibilities
for long-term space voyages and exactly
what space smells like.Q: What do you think will be the most
challenging hurdle for future astronauts
embarking on a long-duration trip
to Mars?
A: I think the biggest risk is radiation. We
need to know how to protect the crew
from it. We need to know the implications
of radiation on our physiology. There are
other challenges, too. We had issues
with our vision [in space]. We had issues
with deconditioning after being in space
for a long time. I think for longer-term
spaceflight — like if we go to the outer
planets of the solar system, where you’ll
have people in space for years — then
artificial gravity is a requirement.Q: So we should be optimistic about long
space trips in the future?
A: I think what NASA’s advertised as the
big [takeaway of the Twins Study so far] is
that we got a lot of data. There are areas
we need to investigate further, like a lot
of genetic stuff. This is the first time we
have ever done any kind of genetic-based
research in space on humans. There are
things with gene expression that I think
they want to dig into further. But overall,
the findings were: “Hey, there are no show-
stoppers in going to Mars.”Q: What about another aspect of being
cooped up in one place for so long —
the smell?
A: You know, every place has its smells.
Generally, I describe the space station’s
smell as a cross between an antiseptic
smell, garbage and BO. Not completely
objectionable, but it often depends on
where you are. If you’re next to the wettrash that’s been sitting on the station for
a few months, it smells more like garbage.
If you’re by the cans that we put the solid
waste in, it might smell a little bit like
that. If you’re by an area that was just at
vacuum [exposed to space] — like after a
spacewalk — it smells kind of like burnt
metal to me, like maybe a sparkler on the
Fourth of July. But it does have a unique
smell.
One time I was getting a tour of the
Harris County jail — not because I did
anything wrong, just a tour — and I walk
into this room with a bunch of prisoners in
there. I had this déjà vu. I was like, [sniffs],
“Almost smells like the space station.”Q: The Twins Study looked at the
physiological impact that long-term
spaceflight has on the human body. But
how did your year in space affect your
mental well-being?
A: I would say the most challenging thing
is you’re isolated. You’re in the same place
every day. You have the same people. Even
though they’re good people that you enjoy
being with, there are a lot of other people
on Earth that are important to you, so you
miss them. You miss going outside. You
miss the weather, the sun, the rain, the
wind. When you go to sleep, you’re at work.
When you wake up, you’re at work. Even
though you like being there, you also like
being home.
One of the cosmonauts, Gennady
Padalka, says, “You know, as astronauts
or cosmonauts, when we’re on Earth, we
dream of space. But when we’re in space,
we dream of Earth.”Left: Astronaut Scott Kelly spent a year aboard
the International Space Station while his identical
twin stayed Earth-side, allowing researchers to
study how spaceflight affects the body. Above:
Kelly (right) faces off with his twin brother, retired
astronaut Mark Kelly.