NASA trained several pairs of eyes on Saturn as the planet put on a dancing light show at its poles. While NASA’s Hubble Space Telescope, orbiting around Earth, was able to observe the northern auroras in ultraviolet wavelengths, NASA’s Cassini spacecraft, orbiting around Saturn, got complementary close-up views in infrared, visible-light and ultraviolet wavelengths. Cassini could also see northern and southern parts of Saturn that don’t face Earth.
The result is a kind of step-by-step choreography detailing how the auroras move, showing the complexity of these auroras and how scientists can connect an outburst from the sun and its effect on the magnetic environment at Saturn. A new video showing aurora images from Hubble and Cassini is available at: http://saturn.jpl.nasa.gov/video/videodetails/?videoID=272.
“Saturn’s auroras can be fickle — you may see fireworks, you may see nothing,” said Jonathan Nichols of the University of Leicester in England, who led the work on the Hubble images. “In 2013, we were treated to a veritable smorgasbord of dancing auroras, from steadily shining rings to super-fast bursts of light shooting across the pole.”
The Hubble and Cassini images were focused on April and May of 2013. Images from Cassini’s ultraviolet imaging spectrometer (UVIS), obtained from an unusually close range of about six Saturn radii, provided a look at the changing patterns of faint emissions on scales of a few hundred miles (kilometers) and tied the changes in the auroras to the fluctuating wind of charged particles blowing off the sun and flowing past Saturn.
While the curtain-like auroras we see at Earth are green at the bottom and red at the top, NASA’s Cassini spacecraft has shown us similar curtain-like auroras at Saturn that are red at the bottom and purple at the top. This is how the auroras would look to the human eye. The color difference occurs because Earth’s auroras are dominated by excited nitrogen and oxygen atoms and molecules, and Saturn’s auroras are dominated by excited forms of hydrogen. Image credit: NASA/JPL-Caltech/Space Science Institute.