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People are big
polluters, on the land, in the sea and even in outer space, that can include
anything from a hammer that floats away from the space station, to radiation
from a nuclear weapons test in the atmosphere.
"This can
range from little chips of paint all the way up to spent rocket bodies and
things like that," said Dan Baker, director of the Laboratory of
Atmosphere and Space Physics at the University of Colorado, Boulder.
"We’ve been trying to figure out how can we most effectively eliminate
this debris without causing more of a problem."
Space debris
travels so fast, even an orbiting chip of paint can poke a hole in a satellite.
But Baker says something tinier, and natural, is a bigger hazard: It’s the
highly charged "killer electrons" of the magnetized zone above the
earth called The Van Allen Belts. "We've observed them to cause very
significant problems for spacecraft," Baker said.
Electro-magnetic
planetary blanket
The doughnut-shaped
Van Allen Belts around our planet protect life on earth from solar winds and
cosmic rays. But their highly energetic charged particles can damage the
circuitry in space stations, weather satellites and other machines that travel
through that region of space. Baker notes that "killer electrons" can
also come from some human activities, like the atmospheric testing of nuclear
weapons.
"Back in
the 1950s and especially in the 1960s, there were nuclear explosions that put
huge amounts of radiation into space that caused many satellites to 'die'
because of radiation damage," he said. "And if that were to happen
today, we know that there are over 1,400 satellites operating in space around
the earth and all of those could be subject to very severe consequences."
Most nations
adhere to treaties that prohibit atmospheric weapon testing. But Baker says
that’s no guarantee. "What is worrisome to us from a political standpoint
today is that there are nations, for example, North Korea and others, that may
be thinking once again, and who may not be adherent to such treaties, that this
might be an interesting way to mess with modern technology," Baker said.
Mysterious space
shield
Radiation
particles in the Van Allen Belts already "mess" with modern
technology. So when satellites must spend time in that region, they are built
with thicker materials. That armor makes them heavier, and more expensive.
Fortunately, spacecraft and satellites that orbit just under the Van Allen
Belts don’t need this heavy shielding. Baker says that’s because, at the lower
edge of the Van Allen Belts, the killer electrons abruptly stop.
He compares it
to the shields that protected Captain Kirk's ship, the Enterprise, from phasers
and asteroids on Star Trek.
Scientists have
known for years that something here on the earth creates an invisible bubble
that clears killer electrons from the lower edge of the Van Allen Belts. Just
what makes that shield has been a mystery. But recently, Baker’s teams figured
out its source. The "bubble maker" is very low frequency radio
transmissions, also known as VLF. Militaries use VLF to communicate with
submarines underwater. It turns out those radio waves also travel up, through
the atmosphere, to the Van Allen Belts.
"So the VLF
bubble is made up of these intense waves. These waves act to sort of scatter
and scrub the inner part of the Van Allen Belts," Baker said, admitting,
"I would prefer that we not be messing with nature. However, in this
particular case I would say that there is some evidence that this is
beneficial."
John Bonnell, a
researcher at the University of California Berkeley's Space Sciences Lab,
agrees that VLF "pollution" is probably benign, and he points to the
high-energy radiation emitted by lightning bolts as evidence.
"We’ve had
natural clearing of the radiation Belts with lightning, for as long as we’ve
had lightning. So in essence, you’ve had a long-running experiment that you can
look at and say, 'Well, if we're going to do things on sort of a sporadic
basis, whereas lightning's been doing it daily for hundreds of millions of
years, the likelihood of there being a bad side effect is pretty
minimal,'" he said.
Bonnell says
that discovering a man-made way to clear killer electrons from the Van Allen
Belt does not mean we will soon create "shields up" devices that use
magnetics or radio transmissions. At least, he says, we’re not making them yet.
"It's a
fascinating possibility and it's a fascinating technology that could enable us
in the future, to explore more of the solar system with people, with robots.
And so it's definitely something that people pick away at slowly over
time," he said.
Bonnell says
scientists, engineers and astronomers have teamed up to make amazing
discoveries about how to study, and travel through, outer space. And while the
future shape of space exploration is a mystery, our new understanding about the
man-made "pollution" that shields satellites may be an important part
of it.