June 3, 2009: In 1972, Apollo astronauts narrowly escaped a potential
catastrophe. On August 2nd of that year, a large and angry sunspot app
eared 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.
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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.
Source:NASA
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