48
ASTRONAUTICSwe cannot pre-
dict the intrave-
hicular radiation
spectrum.
This scenario
further compli-
cates the work
of researchers
engaged in mod-
elling space ra-
diation risk.
It can indeed
be guessed how
the radiation
environment of
a space flight is
unique, complex
and unrepeat-
able in the labo-
ratory. It is the
combination of
some properties
of the particles,
such as charge,
mass and en-
ergy, that de-
termine how
quickly they lose
energy by inter-
acting with mat-
ter.
In the human
body, the dam-
age that a given
organ receives
depends not
only on the en-
ergy spectrum
of the charged particles but also on the
depth and density of the tissue mass that
lies between the skin surface and the tar-
get organ. In general, the heavier the
charged particle, the greater the amount
of energy deposited per unit path length
for that particle. This relationship is re-
ferred to as “linear energy transfer” (LET).
The high-LET radiation found in the GCR
spectrum can produce excessive free radi-
cals that instigate oxidative damage to cell
structures. Chronic exposure to such oxida-
tive stress can lead to premature aging, car-
diovascular disease and cataract formation.T
he schematic
representa-
tion on the left
and the video
above show the
main effects that
space radiation
can have on the
human body dur-
ing a mission to
Mars. [NASA]The precociousness of cataracts in some as-
tronauts is currently the clearest evidence
of what is involved in a long stay in space.
Although the worst consequences are yet
to be demonstrated, the remarkable ioniz-
ing power of GCRs makes it a potentially
significant contributor to tissue damage,
carcinoma onset, central nervous system
degeneration and other deleterious
pathologies.
More worrisome than GCRs on the effec-
tiveness of the crews in the short term are
the so-called “solar particle events” (SPE),
which originate from the breaking of lines
of force of active regions’ magnetic fields
present at the surface of the Sun. These
real explosions hurl into space short-lasting
but very intense flows of ionizing radia-
tion, which, if absorbed by the body of an
astronaut in relevant doses, can cause nau-
sea, vomiting, fatigue, weakness, respira-
tory and digestive diseases, as well as
damage to microcirculation. While these
effects are mostly latent and do not neces-
sarily entail an immediate risk to the crew’s
health, they are at the same time more
than sufficient to compromise many oper-
ations that a long mission requires, as the
individual astronauts may not be able to
carry out their tasks over the course of an
established timeline.
The problems posed by space radiation
seem difficult to solve and will undoubt-
edly further slow down the human explo-
ration of the Moon and Mars.!RADIATION EFFECTS
ON HUMANSACUTE
Felt almost immediately
when a large dose
of radiation is
accumulated in a short
amount of time.
Causesnausea, vomiting
fatigue, and central
nervous system
diseases,which can lead
to changes in motor
function and behavior.CHRONIC
Effects can be
experienced decades
after exposure.
Results from an
accumulated dose of
radiation over a long
period of time.
Causes increased risk of
cancer, cataracts and
vision impairment,
degenerative cardiac
disease.space radiation EN_l'Astrofilo 29/08/2019 15:44 Page 48