MATERIALS | INNOVATION
MAR
TCHOEU LMDA TBERRINIAGL LSI FTEH TAOT
With the right materials, a future for mankind
on the red planet isn’t just science fiction. Philip K. Dick’s 1964 science
fiction novel, Martian Time-
Slip, imagined a human
colony on Mars reliant on
waterways, allotments and robots.
Today, such quaint sci-fi concepts are
actual scientific possibilities now that
we better understand the resources
that are available on the red planet.
Here, Samir Jaber, engineering
content writer at materials search
engine Matmatch, examines how
materials testing could make or break
humanity’s future on Mars.
Elon Musk, SpaceX CEO, believes
that the first sustainable city on Mars
could be a reality in 20 years, with
1000 starships handling the logistics
of the seven-month journey. On the
other hand, in a recent Pew Research
Centre survey carried out in June
2018, only 18% of US adults believed
that sending humans to Mars should
be a high priority. Given our modern
scientific understanding of the red
planet, just how feasible is it that
humans will live and thrive there
during our lifetime?
Firstly, it’s unlikely that Musk’s
envisioned fleet of spaceships will
be overloaded with Earth materials,
as it won’t be feasible to transport all
the materials that we’ll need to live,
subsist and remain safe on Mars over
the long-term.
Instead, the design and civil
engineers of the not-too-distant
future will turn to Mars’ indigenous
resources. Fortunately, the red
planet’s natural resources, and their
possibility to foster human life, are
central to why notions of populating
Mars have moved from fantasy
to scientific plausibility.
For one thing, Mars has carbon that
can be extracted from the atmosphere
and used to make plastics, rocket fuel
or heating fuel. Nitrogen, hydrogen
and oxygen are all biologically
accessible in forms like carbon
dioxide gas, nitrogen gas, and water
ice and permafrost. In-situ resource
utilisation (ISRU) equipment could be
key in exploiting these resources.
BUIDING A NEW SOCIETY
In terms of building materials, Mars’
settlers won’t be short of ceramics
thanks to the ubiquity of clay-like
materials in Martian soil. There are
also plentiful mineral resources
including iron, titanium, nickel,
aluminium, sulphur, chlorine and
calcium.
Silicon dioxide is the most
common material on Mars, according
to measurements taken by the Viking
space probes, and is also a basic
ingredient of glass. It is likely that
glass products, including fiberglass,
and structures could be constructed
on Mars in a similar way as they are
on Earth.
Regolith is another readily
available Martian construction
material that researchers think could
be a viable alternative for concrete.
The pulverised, dusty rock — that’s
mostly silicon dioxide and ferric
oxide, with a fair amount of aluminium
oxide, calcium oxide and sulphur
oxide — has been deposited over
Mars by asteroid collisions over
billions of years.
Regolith samples
have yet to be
brought back to
Earth but a regolith simulant, JSC
Mars-1a, is a very close replica
of Martian soil. It is 43.48% silicon
dioxide and 16.08% iron oxide
by weight, compared with actual
Martian regolith that is, on average,
45.41% silicon dioxide and 16.73%
iron oxide. JSC Mars-1a has been
used to explore the possibility of the
use of regolith in 3D printing. Could
NASA one day send robots to 3D print
regolith layer-by-layer, and gradually
build the cities imagined by Musk?
But how strong would Martian
concrete be? Mars has a lot of sulphur
in its soil, and molten sulphur is used
to bind some concrete on Earth. Tests
at Northwestern University, Illinois,
US, have mixed melted sulphur with
JSC Mars-1a in a ratio of 1:3, the same
recipe used for sulphur concrete
on Earth. Tests of the simulated
Martian concrete’s strength under
compression, bending and splitting
found it to be much weaker compared
with concrete made using Earth
sand. This was attributed to the
Martian sand’s porosity. The Earth
composition’s compression strength
was about 30 megapascals (MPa),
similar to that of cement-based
concrete.
Further experiments with a 1:1
sulphur-to-sand mix compressed
the mixture, broke down grains and
drove out air bubbles. This resulted
in a strength of 60 MPa. Sulphurbased
concrete also has quick-setting
advantages, offering more immediate
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