+ Play
Audio
|
+ Download Audio | +
Email to a friend | +
Join mailing list
June
3, 2009: In 1972, Apollo astronauts narrowly escaped
a potential catastrophe. On August 2nd of that year, a large
and angry sunspot appeared and began to erupt, over and over
again for more than a week, producing a record-setting fusillade
of solar proton radiation. Only pure luck saved the day. The
eruptions took place during the gap between Apollo 16 and
17 missions, so astronauts missed the storm.
Researchers
still wonder, what would have happened if the timing had been
just a little different, what if astronauts had been caught
unprotected on the surface of the Moon?
Right:
One of the August 1972 solar flares. Click on the image to
launch a movie recorded at the Big Bear Solar Observatory.
NASA
needs to know. The agency is in high gear preparing to send
people to the Moon to set up a manned outpost, a step toward
eventually sending humans to Mars or elsewhere in the solar
system. These missions will take astronauts outside the protection
of Earth's magnetic field for months or even years at a time,
and NASA must know how to keep its explorers safe from extreme
solar storms.
So
scientists are creating an artificial solar radiation storm
right here on Earth. And they're testing its effects on an
artificial human: Matroshka, the Phantom Torso.
The
European Space Agency's Matroshka and his NASA counterpart Fred
have already flown in experiments aboard the Space Shuttle and
the International Space Station that have shown how other kinds
of space radiation such as cosmic rays penetrate the human body.
Now, scientists at Brookhaven National Laboratory in Upton,
New York, are subjecting an artificial torso to a beam of protons
to learn how astronauts would be affected by the 1972 event.
"We
want to know how close it comes to a dangerously acute exposure,"
says Francis Cucinotta, the Chief Scientist for NASA's Radiation
Program at the Johnson Space Center in Houston, Texas.
In
the parlance of radiation experts, "acute exposure"
is brief but intense. Radiation strikes the body over a relatively
short period of time ranging from minutes to hours—just like
a solar flare. This is different from the "chronic exposure"
astronauts normally experience as they travel through space.
Cosmic rays hit their bodies in a slow drizzle spread out
over weeks or months. With chronic exposure, the body has
time to repair or replace damaged cells as it goes along,
but an acute exposure gives the body little time to cope with
the damage.
Above:
The radiation beamline at NASA's Space radiation Lab in Brookhaven.
[Larger image]
"The
biological effects are very sensitive to the dose rate,"
Cucinotta explains. "A dose of radiation delivered over
a short amount of time is two to three times more damaging
than the same dose over a few days."
At
first glance, the 1972 event would seem to fall into the acute
category—it was after all a solar flare. But there's a problem.
It was actually a series of flares producing a radiation storm
that was longer and less impulsive than normal. Radiation
exposure would have been neither chronic nor clearly acute,
but somewhere in between. In this gray area, details about
how much of the radiation actually reaches a person’s vital
organs — versus how much is blocked by their spacesuit, skin
and muscles — can make all the difference.
Matroshka
is helping scientists understand these details. He's a life-size
plastic replica of a human torso, sans arms and legs. The
plastic closely matches the density of organs and tissues
in the human body, and this Phantom Torso is embedded with
hundreds of radiation sensors throughout his body. He even
has real human blood cells.
Right:
Matroshka in and out of his white traveling poncho. [Larger
image]
"We
put blood cells in small tubes in the stomach and in some
places in the bone marrow," some of which are deep within
the torso while others are close to the surface where there's
less "tissue" to block radiation. "One of the
questions we have is whether the less shielded parts of the
bone marrow will be [much harder hit]," raising the risks
of leukemia and other cancers.
Using
real blood cells lets scientists see how much the radiation
damages the cells' DNA. High-speed particles of proton radiation
can smash into DNA, breaking the string-like molecules. Cells
can usually repair these breaks, but if several breaks occur
within a short period of time, the damage can be irreparable.
At best, the cell will then self-destruct. At worst, it will
go haywire and grow out of control, becoming cancerous.
To
subject Matroshka to a 1972-style radiation storm, scientists
have devised a way to simulate that event using a high-energy
proton beam at NASA's Space Radiation Lab in Brookhaven. The
beam fans out so that, at the point where Matroshka sits,
it's 60 cm across — large enough to engulf the entire torso.
By stepping the energy of the beam through a series of energy
levels, scientists can mimic the unique energy spectrum of
the protons in the 1972 event.
In
the upcoming experiment, led by Guenther Reitz of the German
Aerospace Center (DLR) in Cologne, Matroshka's radiation sensors
will reveal how much proton radiation reaches various parts
of the mannequin's body. "With protons, you might have
an order of magnitude (a factor of ten) difference from one
part of the body to another," notes Cucinotta.
The
readings will help mission planners figure out how much shielding
is necessary to protect real astronauts from a 72-style storm.
The results will also point researchers in the right direction
for medical treatments that might help mitigate the effects
of such an event.
Unlike
a real astronaut, Matroshka can withstand multiple flares
with no lasting side effects. A quick transfusion of blood
cells and voilà--Matroshka is ready for another blast.
So
let the flares begin—and stay tuned for results.
SEND
THIS STORY TO A FRIEND
Author: Dr.
Tony Phillips | Credit: Science@NASA
|