http://www.newscientist.com/article.ns?id=dn6897
Columbia crew saw new atmospheric phenomenon
12:02 19 January 2005
NewScientist.com news service
Maggie McKee
A new atmospheric phenomenon was caught on video by the crew of the space
shuttle Columbia just days before the shuttle broke apart, new findings
suggest.
Astronauts relayed the video to NASA in real-time during their 16-day flight.
But the agency did not release the full data to researchers until several
months after the mission's tragic end on 1 February 2003. All seven crewmembers
were killed when the shuttle exploded while re-entering the atmosphere.
Yoav Yair of the Open University in Ra'anana, Israel, and colleagues spent more
than a year analysing the video, which was originally taken to study
atmospheric dust. But a single frame of the video - representing just 33
milliseconds - shows a mysterious reddish glow in the night sky on 20 January
2003.
"I'm not sure what we saw," says Yair. "I just know it wasn't something we were
used to seeing - it was something extraordinary." The glow occurred about 150
kilometres above the ocean near Madagascar and does not appear to be linked
with thunderstorms.
That contrasts sharply with other ephemeral events at similar altitudes, which
glimmer into being when electrical current travels upward from lightning clouds
at altitudes of about 10 km. Called sprites and elves, these events take the
shape of jellyfish, downward-pointing carrots, or doughnuts, and tend to occur
within a horizontal distance of 70 km from lightning.
Wrong type of lighting
But the closest lighting picked up by the shuttle's video camera was 800
kilometres away from the unexplained glow, which has been dubbed a TIGER
(Transient Ionospheric Glow Emission in Red). Most sprites and elves emerge
within a few milliseconds of the nearest lightning strike, but the TIGER took
250 milliseconds to leap into view after this lightning struck, suggesting the
two events were not linked.
Even a far-distant lightning storm is unlikely to have caused the TIGER, says
Yair. Some theorists think that powerful lightning bolts may send out beams of
electrons that get shot to far-flung places along Earth's magnetic field lines.
In fact, a different lightning bolt did strike at the right time around Cyprus
- the predicted starting point of a magnetic "loop" that ends at Madagascar.
But it was the wrong type of strike, sending negative charge toward the ground
rather than the predicted positive charge.
Walter Petersen, a lightning expert at the University of Alabama in Huntsville,
US, who is not part of the team, agrees that the new event appears unrelated to
lightning. "My next guess is some kind of meteor - something coming down into
the atmosphere from above," he told New Scientist.
But Yair says the new observation does not fit the profile of a meteor. Meteors
cause the atmosphere to glow more brightly than this event, and they trace out
long streaks that can be seen for hundreds of milliseconds - much longer than
the TIGER.
Even more new atmospheric "species" may turn up with future observations from
satellites or the International Space Station, says Yair.
And he adds that the observation of the TIGER adds to the scientific
discoveries of the mission, honouring the lives of the lost astronauts. "Of
course, it's no consolation. But it shows the astronauts didn't die for nothing
- some science was achieved," he told New Scientist.
Journal reference: Geophysical Research Letters (vol 32, L02801)
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