ROOM
40
Astronautics
used to address bone loss caused by radiation and
microgravity exposure.
Reduced gravity
The consequences of prolonged microgravity on
the human body - osteopenia and osteoporosis
(the long-term loss of bone mass), muscle atrophy,
reduced healing, changes in fluid distribution
throughout the body, intervertebral disc expansion
and reduced sensorimotor function - have been
studied extensively.
Frequent exercise and pharmaceuticals offer
mitigation while in space. Some effects, such as
the loss of bone mass, can be permanent while
other effects, such as changes to the distribution
of fluids within the body, are temporary and will
resolve upon return to a gravity environment.
Interestingly, there is little to no information
available on the long-term effects of a partial gravity
environment on the human body. There have only
been 12 humans who have travelled to the surface of
another celestial body and those missions were all
relatively short. All long-duration human habitation
space missions have occurred in space stations
in low Earth orbit (LEO), which can only support
research in microgravity, not partial gravity.
The relationship between gravity and health is not
necessarily a linear one and computer modelling
suggests the reduced gravity of Mars is, for the
purposes of human health, more similar to Earth-
level gravity than it is to microgravity. This research
suggests that any negative effects of Martian gravity
on human colonists could be relatively manageable
and current countermeasures should be sufficient.
However, until long-duration human research is
conducted in a true partial gravity environment this
is simply an educated guess.
Circadian dysrhythmias
Sleep is essential for human health as well as for
human performance. In a Mars colony, optimal
functioning will be crucial for maintaining critical
systems and performing operations - fatigue would
become a threat to overall health.
The term ‘circadian rhythm’ describes the
natural biological clock of organisms; on Earth,
that cycle is approximately 24 hours long.
Disruptions can result in fatigue, decreased
alertness and performance failure; in space,
those disruptions can include an intense
workload, confinement, and the loss of the
light/dark cycle that comes with experiencing
day and night.
While the Martian day (sol) is only 39 minutes
longer than an Earth day and so within the likely
shielding technology will also be necessary.
Shielding against SPE radiation, due to its
relatively lower energy, can be achieved with
existing technology. Aluminium or regolith
(Martian soil) could be used to protect habitats on
the Martian surface; the use of caves as habitats
that reach sufficiently deep underground has also
been proposed.
In general, short-duration human extra vehicular
activities (EVA) of a few hours at a time outside of the
habitat would not likely result in significant radiation
exposure, though anyone working on the Martian
surface would need to remain close to appropriate
shelters in case of solar storms or an intense SPE, for
which a deep space SPE alert warning system would
need to be created.
Higher energy GCR is more challenging and
research examining shielding effectiveness suggests
that only small reductions to GCR are possible using
current technology.
Pharmaceutical countermeasures against
symptoms of radiation may also prove useful,
although no drugs currently exist that mitigate long-
term effects.
Some medications may reduce radiation-
associated symptoms like nausea and vomiting while
other drugs with radio-protective properties, such
as amifostine or antioxidants in general, can serve
as direct countermeasures, although they may have
side effects. Research on mice has suggested that
a class of drugs called bisphosphonates may be
Future Mars
settlements may be
partially buried to reduce
radiation impact, as this
cutaway view shows.
Interestingly, there is little to no information
available on the long-term effects of a partial
gravity environment on the human body
NASA/Ames
