Sky & Telescope - May 2019 - 12

COSMIC RELIEF by David Grinspoon

One Small
Step for
Plantkind
With a germinating seed on the
lunar farside, Earth's biosphere
makes its ﬁrst tentative foray
into the cosmos.

M AY 2 0 1 9 * S K Y & T E L E S C O P E

p GROWING GEAR Clockwise from top: China's Change'4 lander at its touchdown spot on the
lunar farside, in an image taken by the rover; the cotton sprouts during their abbreviated life on the
Moon, with encroaching ice hinting at their imminent demise; and the LME experiment canister.

ing oxygen and carbon dioxide like a
mini-Gaia.
The experiment didn't go as hoped.
The cotton seeds did sprout, providing
an inspiring photo-op, but they didn't
survive the coming of night. Unfortunately, during that ﬁrst long, frozen
lunar night, the LME's thermal control
failed, and the young sprouts, along with
the still-unhatched ﬂies, froze to death.
While it's true that plants can't go to
the Moon or Mars without us, it's also
true that we can't go to Mars - at least
to stay - without plants and myriad
other living things. If we want to survive we'll need to learn how to keep our
nonhuman companions happy.
One famous experiment attempted
along these lines in the early 1990s
was Biosphere 2. An enclosed habitat in the Arizona desert, Biosphere 2
bore a complement of species meant to
simulate a range of terrestrial ecosystems. These microhabitats would recycle
gases, water, and nutrients in order to
keep the enclosure's humans and other
beings alive.
The exercise failed when runaway
growth of some species, die-offs of others, and dangerous changes in the O2

and CO2 levels meant that the human
"biospherians" could not safely remain
inside. Fortunately, it was easy to abandon ship, as this experiment was here
and not on Mars.
Today, Biosphere 2 serves as a teaching and research facility, and studies
involving enclosed people are no longer
attempted there. Recently I got a tour,
and it's a fascinating time capsule - a
vision of the future fading into the
past. But it's also a monument to both
arrogance and humility, a lasting lesson
in what can go wrong when we think
we know more than we do. Our planet's
environment maintains the complex
balance of life so gracefully that it's easy
to take for granted.
Like Biosphere 2, the Chinese trial is
a sobering reminder that we still have
an awful lot to learn about life and
its mutual dependencies if we want to
someday go and live beyond our home
biosphere. Raising a plant on the Moon,
even for a brief time, is a welcome tiptoe in that direction.
■ Astrobiologist DAVID GRINSPOON has
tried to grow many plants on Earth, and
some have even lived for a short while.

L A NDER: A FP / G E T T Y IM AG ES; CA NISTER: CHONQ ING UNIV ERSIT Y;
SPROU T: CHONQ ING UNIV ERSIT Y / A FP / G E T T Y IM AG ES

IN JANUARY THE CHINESE space agency
achieved an impressive ﬁrst, landing
Chang'e 4, which also held the Jade Rabbit 2 rover, on the lunar farside. One of
the most sensational image releases from
this mission showed germinating cotton
seeds growing inside the lander.
These aren't the ﬁrst plants raised
in space. Astronauts have long used
the International Space Station, for
example, for biological experimentation, including studies of how plants
grow when subjected to low gravity and
radiation. But there's symbolic potency
in the ﬁrst plants (that we know of)
born on the surface of another world.
Call it one small step for plantkind.
Yet these organisms couldn't have
achieved this by themselves, so this is
really another small step for humankind. It may not be a giant leap, but if
humans are ever to go and live elsewhere in the solar system, not just for
a visit but to remain, we'll have to take
our biospheres with us and learn how to
tend them there.
Among the experiments onboard
Chang'e 4 is the apparatus that contained the cotton seeds - the Lunar
Micro Ecosystem (LME). It also carried
seeds of several other kinds of plants as
well as yeast and fruit ﬂy eggs. The plan
was to keep the receptacle at Earth-like
temperatures for 100 days while the
plants sprouted and the ﬂies hatched,
setting up a miniature ecosystem in
which the animals respired and the
vegetation photosynthesized, exchang-

Sky & Telescope - May 2019

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