Polar lightning - not just an earthly phenomenon: study
Chicago (AFP) Oct 9, 2007
Images from a NASA probe have shown that lightning does occur at the poles on Jupiter, a phenomenon previously only seen on Earth, a study released Tuesday said.
Lightning strikes had previously been observed at lower latitudes and around the equator on the gas planet but the jagged bolts of electricity had never been observed at either of its two poles, puzzling astronomers.
But as it rocketed past Jupiter on its way to Pluto in March this year, NASA's New Horizons spacecraft snapped hundreds of images of the Jupiter system, yielding dazzling new data and previously unseen glimpses of the planet.
Images taken by the probe's Long Range Reconnaisance Imager revealed six flashes of light in the north polar region and seven in the south.
The most polarward strikes were at 80 degrees north and 74 degrees south. Some of the bolts were ten times as powerful as anything ever recorded on Earth.
"This validates what we have thought for 20 years. Jupiter is behaving like it should," said Kevin Baines, a planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, and lead author of the paper.
A giant ball of gas and liquid, Jupiter radiates about twice as much heat into space as it receives from the sun. Based on the laws of physics, the planet should radiate heat uniformly which should produce lightning strikes uniformly as the heat moves through water clouds.
New Horizons was the eighth spacecraft to visit Jupiter but a combination of trajectory, timing and technology allowed it to explore details no probe had seen before.
The images provided evidence on the life cycle of fresh ammonia clouds, boulder-size clumps speeding through the planet's faint rings and the structure inside volcanic eruptions on its moon Io.
The New Horizons probe -- the fastest spacecraft ever launched -- blasted off from Cape Canaveral, Florida in January 2006 and is expected to reach Pluto and its moons by 2015.
The paper appears in the journal Science.
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