NASA JPL Cassini | 22 Sept 2010
A new movie and images showing Saturn's shimmering aurora over a two-day period are helping scientists understand what drives some of the solar system's most impressive light shows.
The movie and images are part of a new study that, for the first time, extracts auroral information from the entire catalogue of Saturn images taken by the visual and infrared mapping spectrometer instrument (VIMS) aboard NASA's Cassini spacecraft. These images and preliminary results are being presented by Tom Stallard, lead scientist on a joint VIMS and Cassini magnetometer collaboration, at the European Planetary Science Congress in Rome on Friday, Sept. 24.
In the movie, the aurora phenomenon clearly varies significantly over the course of a Saturnian day, which lasts around 10 hours 47 minutes. On the noon and midnight sides (left and right sides of the images, respectively), the aurora can be seen to brighten significantly for periods of several hours, suggesting the brightening is connected with the angle of the sun. Other features can be seen to rotate with the planet, reappearing at the same time and the same place on the second day, suggesting that these are directly controlled by the orientation of Saturn's magnetic field.
...
The new, false-color images show Saturn's aurora glowing in green around the planet's south pole. The auroral information in the two images was extracted from VIMS data taken on May 24, 2007, and Nov. 1, 2008. The video covers about 20 Earth hours of VIMS observations, from Sept. 22 and 23, 2007.
Glowing Southern Lights
This false-color composite image, constructed from data obtained by NASA's Cassini spacecraft, shows the glow of auroras streaking out about 1,000 kilometers (600 miles) from the cloud tops of Saturn's south polar region. It is among the first images released from a study that identifies images showing auroral emissions out of the entire catalogue of images taken by Cassini's visual and infrared mapping spectrometer.
In this image constructed from data collected in the near-infrared wavelengths of light, the auroral emission is shown in green. The data represents emissions from hydrogen ions in of light between 3 and 4 microns in wavelength. In general, scientists designated blue to indicate sunlight reflected at a wavelength of 2 microns, green to indicate sunlight reflected at 3 microns and red to indicate thermal emission at 5 microns. Saturn's rings reflect sunlight at 2 microns, but not at 3 and 5 microns, so they appear deep blue. Saturn's high altitude haze reflects sunlight at both 2 and 3 microns, but not at 5 microns, and so it appears green to blue-green. The heat emission from the interior of Saturn is only seen at 5 microns wavelength in the spectrometer data, and thus appears red. The dark spots and banded features in the image are clouds and small storms that outline the deeper weather systems and circulation patterns of the planet. They are illuminated from underneath by Saturn's thermal emission, and thus appear in silhouette.
The composite image was made from 65 individual observations by Cassini's visual and infrared mapping spectrometer on Nov. 1, 2008. The observations were each six minutes long.
Credit: NASA/JPL/University of Arizona/University of Leicester
Four Aurora Snapshots
A quartet of false-color, composite images show the dance of Saturn’s southern lights in data obtained by NASA’s Cassini spacecraft. This image is among the first images to be released from a study that extracts auroral emissions out of the entire catalogue of images taken by Cassini’s visual and infrared mapping spectrometer.
In this image constructed from data collected in the near-infrared wavelengths of light, the auroral emission is shown in green. The data represents emissions from hydrogen ions in of light between 3 and 4 microns in wavelength. In general, scientists designated blue to indicate sunlight reflected at a wavelength of 2 microns, green to indicate sunlight reflected at 3 microns and red to indicate thermal emission at 5 microns. Saturn's rings reflect sunlight at 2 microns, but not at 3 and 5 microns, so they appear deep blue. Saturn's high altitude haze reflects sunlight at both 2 and 3 microns, but not at 5 microns, and so it appears green to blue-green. The heat emission from the interior of Saturn is only seen at 5 microns wavelength in the spectrometer data, and thus appears red. The dark spots and banded features in the image are clouds and small storms that outline the deeper weather systems and circulation patterns of the planet. They are illuminated from underneath by Saturn's thermal emission, and thus appear in silhouette.
The images that make up the composite were obtained on May 24, 2007.
Credit: NASA/JPL/University of Arizona/University of Leicester
Dancing Southern Lights of Saturn
This movie, made from data obtained by NASA's Cassini spacecraft, shows Saturn's southern aurora shimmering over approximately 20 hours as the planet rotates. This video is among the first videos released from a study that extracts auroral emissions out of the entire catalogue of images taken by Cassini's visual and infrared mapping spectrometer.
In this movie constructed from data collected in the near-infrared wavelengths of light, the auroral emission is shown in green. The data represents emissions from hydrogen ions in of light between 3 and 4 microns in wavelength. In general, scientists designated blue to indicate sunlight reflected at a wavelength of 2 microns, green to indicate sunlight reflected at 3 microns and red to indicate thermal emission at 5 microns. Saturn's rings reflect sunlight at 2 microns, but not at 3 and 5 microns, so they appear deep blue. Saturn's high altitude haze reflects sunlight at both 2 and 3 microns, but not at 5 microns, and so it appears green to blue-green. The heat emission from the interior of Saturn is only seen at 5 microns wavelength in the spectrometer data, and thus appears red. The dark spots and banded features in the image are clouds and small storms that outline the deeper weather systems and circulation patterns of the planet. They are illuminated from underneath by Saturn's thermal emission, and thus appear in silhouette.
The movie covers just under two Saturnian days, from 2:15 p.m. UTC on Sept. 22, 2007 to 10:53 a.m. on Sept. 23, 2007. The spacecraft viewing angle stays the same, so that throughout the video. The aurora can clearly be seen to vary significantly over the period of the observation. On the noon and midnight sides (left and right, respectively), the aurora brightens significantly for extended periods of several hours, suggesting the brightening is connected with the direction of the sun. Other features appear to rotate with the underlying planet, suggesting that these are directly controlled by the direction of Saturn's magnetic field.
Scientists processed the auroral emissions to the fullest extent allowed by the spectrometer data.
Credit: NASA/JPL/University of Arizona/University of Leicester
Play video
