THE clearest ever pictures of spectacular auroras on Saturn have been
beamed back from the Hubble Space Telescope. Ten times sharper than earlier
pictures, the ultraviolet images will help to pin down the composition of
Saturn鈥檚 atmosphere.
Guided by the planet鈥檚 magnetic field, charged particles streaming from the
Sun strike its atmosphere, where they excite molecules and make them glow. An
instrument called the Space Telescope Imaging Spectrograph, installed on Hubble
last year, recorded the above image.
Similar views of Jupiter鈥檚 auroras have revealed two bright streaks where a
million amps of electric current flowed from its moon Io to the planet鈥檚
atmosphere. 鈥淲e鈥檝e never seen the streaks before, and right now we don鈥檛 know
how to explain them,鈥� says John Trauger of the Jet Propulsion Laboratory in
Pasadena, California. He described the images at a meeting of the American
Astronomical Society in Washington DC last week.
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