too dangerous. It goes without saying: You
should not try burning hydrogen and oxy-
gen at home. Watney had no other available
option, and he was extremely careful to burn
hydrogen and oxygen slowly enough to avoid
blowing himself up.
Mars is considered the next frontier in
human space flight. Scientists think the Red
Planet could host or have hosted life millions
of years ago. It is the closest world to us that
could host life, even if this life is in the form
of microbes. By the time
humans set foot on Mars,
you may be in the class of
astronauts selected for the
journey to the Red Planet.
Watney had a difficult
time during his visit to
Mars, but it was chemistry that ultimately
saved his life!
Also, studies suggest that watering plants
on Mars could require less water than on
Earth. That is because water would flow
differently through the Martian soil, thanks
to the Red Planet’s gravity, which is approximately 38% that of Earth’s. In other words,
anything on Mars would feel about three times
lighter than on Earth. Therefore, under Martian
gravity, the soil can hold more water than on
Earth, and water and nutrients within the soil
would drain away more slowly.
Some conditions would make it difficult for
plants to grow on Mars. For example, Mars’s
extreme cold temperatures make life difficult
to sustain. Sunlight and heat reaching that
planet is much less than what the Earth gets.
This is because Mars is about 50 million miles
farther away from the sun. Also, the Martian
atmosphere is not as thick as Earth’s atmosphere, which keeps our planet warm.
In The Martian, when Watney accidentally
exposes his farm to Mars’s cold temperatures, his potato plants freeze to death almost
instantly. As mentioned earlier, Mars’s open
air is just too cold for plants to survive.
Making water on Mars
Water available from the Hab was not
enough to sustain Watney or his farm until
NASA rescued him. However, Watney was
clever enough to think of a way to make water
from scratch and irrigate his potatoes.
Making water does not sound like a complicated process: take oxygen, add hydrogen,
and burn them together to create water. But
Watney did not have hydrogen at his disposal.
The oxygen, on the other hand, was easy to
get. The Hab’s oxygenator liberated oxygen
from the abundant carbon dioxide in the Martian atmosphere.
To obtain hydrogen, Watney used hydrazine
(N2H4), an inorganic compound widely used
to propel rockets, satellites, and spacecraft,
which was available from his mission to
Mars. He had hundreds of liters of unused
hydrazine. Watney dissociated hydrazine into
nitrogen and hydrogen, and then, he burned
2 H2 + O2 ; 2 H2O
Is it possible to create water from scratch?
Not really, since creating water from scratch
by burning hydrogen and oxygen would be
To carry out photosynthesis, plants also
need various nutrients, such as nitrogen,
potassium, and phosphorus. Nitrogen is a
key component of chlorophyll, the compound
responsible for the green color of plants and
for capturing the light needed for photosynthesis. Potassium helps to open and close
tiny pores in leaves and stems that take in
the water and the carbon dioxide used in
photosynthesis. Phosphorus is involved in the
chemical reactions that make up photosynthesis.
In contrast with plants, human beings and
animals cannot harvest solar energy. Instead,
humans get their energy from eating food,
which comes from animals and plants and
provides the energy humans need to survive.
Animals also get their energy from plants or
other animals that eat plants. In that sense,
everything we eat was once a plant.
Growing crops on Mars
It is not easy to predict what we will or
will not be able to do when we set foot on
Mars. But as far as the chemistry that was
conducted in The Martian, Watney’s scientific
method checks out. Scientists have conducted
plant experiments simulating Martian conditions using volcanic soil in Hawaii, which is
known for its similarity to Martian soil. These
experiments found that plants can actually
grow in these soils.
There are other aspects future Mars explorers will need to consider when growing plants
on that planet. As mentioned earlier, Mars’s
atmosphere is mostly carbon dioxide, and
plants need this gas just as much as we need
oxygen to breathe.
Weir, A. The Martian. New York: Crown
Kinberg, S. (Producer); Scott, R. (Director). The
Martian [Motion Picture]. United States: 20th
Century Fox, 2015.
Mars: Extreme Planet. All About Mars. Mars
Exploration. National Aeronautics and Space
Administration: http://mars.nasa.gov/allabout-mars/extreme/ [accessed Feb 2017].
Hooper, R. The Martian: The Science of Surviving a
Space Catastrophe. New Scientist, Sept 25, 2015:
the-martian-the-science-of-surviving-a-space-catastrophe/ [accessed Feb 2017].
Roberto Molar Candanosa is a science writer who
lives in Washington, D.C. This is his first article in
This experiment at Utah’s Mars Desert Research
Station looked at the effects of temperature and
atmosphere on plant growth in the station.
Since the late 1980s, NASA plant scientists have
been studying how to grow potatoes (such as the
ones shown here) in hydroponic solutions, which
are expected to be used on missions to Mars.