Gravity isn’t the only thing that
the Earth provides for our bodies.
The thick atmosphere and global
magnetic field that cocoons our
planet protect the surface from
cosmic rays. These are energetic
radiation particles – spat out
by flares on the Sun or accelerated
to nearly the speed of light
by supernova events – that are
exceedingly hazardous to cells.
Astronauts aboard the ISS,
and, in particular, any future
spacefarers voyaging to the Moon,
Mars and beyond will be exposed to
this nasty space radiation. These
energetic particles damage DNA,
causing mutations and could
potentially trigger tumours and
cancer, and they also turn the lenses
of your eyes opaque. But what we
understand much less clearly is
what irreversible effects cosmic rays
might have on your immune system,
or on your brain’s neurons.
Astronauts can be protected against
cosmic rays by providing several
metres of radiation shielding to
absorb the particle bombardment,
and this would be relatively simple
on the lunar or Martian surface
by burying the crew quarters
underground. But providing complete
shielding around a spaceship would
make it impossibly massive andexpensive. So, instead of blocking the
radiation, another countermeasure
would be to reduce its harmful effects
within the body. Dietary supplements
and drugs could be taken to mop up
free radicals produced in your cells
by radiation, or to help with DNA
repair. The problem, says radiation
physicist Dr Marco Durante, is that
current antioxidant supplements
aren’t particularly effective, whereas
radioprotector drugs like Ethyol do
work but are pretty toxic. Ethyol, for
example, is only occasionally used
with patients who have cancer in
the head and neck region, where
the side effects of radiotherapy are
often severe. “The US Department
of Defense has developed several
compounds in the framework of
the homeland security program,
and testing these for their
effectiveness against cosmic rays
in astronauts would be very
interesting,” Durante says. “As an
alternative to drugs, one promising
biomedical process is hibernation,
because radioresistance seems to
be increased at low temperature.”
If we can work out how to keep
the human body in a state of
cryogenic suspension, the crew could
sleep through the whole eight-month
flight to Mars, and the freezing cold
would also help protect their cellsfrom radiation damage. And, if
the astronauts are not active, it will
also mean that the demands on
the life-support system, and the
amount of food and other
consumables that will be needed,
will also be greatly reduced.
But, perhaps, we could go one
better. Could it be possible to
genetically modify future astronauts
to enhance their radiation resistance?
New research on strange microscopic
animals know as tardigrades
elucidates one route we might
go down. Takekazu Kunieda,
a molecular biologist at the
University of Tokyo, has been
working on these tiny ‘water bears’
that are known to be able to survive
extremely hostile conditions such as
the vacuum of space and punishingly
high radiation levels. To try to
understand which genes might be
behind these prodigious survival
skills, Kunieda sequenced the
tardigrade’s genome and then inserted
sections of this DNA into mammalian
cells in a petri dish. In this way, they
found a new gene dubbed Dsup (for
‘damage suppressor’), which acted
to prevent the tardigrade’s DNA
from breaking under radiation.
And astonishingly, this gene also
reduced radiation-induced DNA
damage by 40 per cent in human cells.[ RADIATION ]
Mars colonists
would need to shield
their base from
dangerous cosmic
raysSpace
Science
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