This is a series of images of Saturn, as seen at many different
wavelengths, when the planet’s rings were at a maximum tilt of
26 degrees toward Earth. Saturn experiences seasonal tilts away
from and toward the Sun, much the same way Earth does. This
happens over the course of its 29.5-year orbit. This means that
approximately every 30 years, Earth observers can catch their
best glimpse of Saturn’s South Pole and the southern side of the
planet’s rings. Between March and April 2003, researchers took
full advantage to study the gas giant at maximum tilt. They used
NASA’s Hubble Space Telescope to capture detailed images of
Saturn’s Southern Hemisphere and the southern face of its rings.

The telescope’s Wide Field Planetary Camera 2 used 30 filters to
snap these images on March 7, 2003. The filters span a range of
wavelengths. “The set of 30 selected filters may be the best
spectral coverage of Saturn observations ever obtained,” says
planetary researcher Erich Karkoschka of the University of Arizona.
Various wavelengths of light allow researchers to see important
characteristics of Saturn’s atmosphere. Particles in Saturn’s
atmosphere reflect different wavelengths of light in discrete
ways, causing some bands of gas in the atmosphere to stand out
vividly in an image, while other areas will be very dark or dull.
One image cannot stand by itself because one feature may have
several interpretations. In fact, only by combining and comparing
these different images, in a set such as this one, can researchers
interpret the data and better understand the planet.

By examining the hazes and clouds present in these images,
researchers can learn about the dynamics of Saturn’s atmosphere.
Scientists gain insight into the structure and gaseous composition
of Saturn’s clouds via inspection of images such as these taken by
the Hubble telescope. Over several wavelength bands, from infrared
to ultraviolet, these images reveal the properties and sizes of
aerosols in Saturn’s gaseous makeup. For example, smaller aerosols
are visible only in the ultraviolet image, because they do not
scatter or absorb visible or infrared light, which have longer
wavelengths. By determining the characteristics of the atmosphere’s
constituents, researchers can describe the dynamics of cloud
formation. At certain visible and infrared wavelengths, light
absorption by methane gas blocks all but the uppermost layers of
Saturn’s atmosphere, which helps researchers discern clouds at
different altitudes. In addition, when compared with images of
Saturn from seasons past (1991 and 1995), this view of the planet
also offers scientists a better comprehension of Saturn’s seasonal
changes.

Credit: NASA and E. Karkoschka (University of Arizona)

Electronic images and additional information are available at
http://hubblesite.org/news/2003/23

The Space Telescope Science Institute (STScI) is operated by the
Association of Universities for Research in Astronomy, Inc. (AURA),
for NASA, under contract with the Goddard Space Flight Center,
Greenbelt, MD. The Hubble Space Telescope is a project of
international cooperation between NASA and the European Space
Agency (ESA).