(See description below)
Titan's Atmosphere
This image shows a thin, detached haze layer that
appears to float above the main atmospheric haze. Because of its
thinness, the high haze layer is best seen at the moon’s
limb. The Voyager spacecraft detected such detached haze layers
on Titan during their flybys in the early 1980s. Click here for a close-up of the
detached layer.
The image, which shows Titan’s southern polar region, was
taken using a spectral filter sensitive to wavelengths of
ultraviolet light centered at 338 nanometers. The image has been
false-colored to approximate what the human eye might see were
our vision able to extend into the ultraviolet: The globe of
Titan retains the pale orange hue our eyes usually see, and both
the main atmospheric haze and the thin detached layer have been
given their natural purple color. The haze layers have been
brightened for visibility.
The best possible observations of the detached layer are made in
ultraviolet light because the small haze particles which populate
this part of Titan’s upper atmosphere scatter short
wavelengths more efficiently than longer visible or infrared
wavelengths; this accounts for the bluish-purple color.
Images like this one reveal some of the key steps in the
formation and evolution of Titan's haze: The process begins in
the high atmosphere (at altitudes higher than 600 km or 370 mi),
where solar ultraviolet light breaks down methane and nitrogen
molecules. The products react to form more complex organic
molecules containing carbon, hydrogen and nitrogen, and these in
turn combine to form the very small particles seen as high hazes.
The small particles stick upon collision with one another,
forming larger particles which fall deeper into the atmosphere to
maintain the lower main haze layer which is thick enough to
obscure the surface at visible wavelengths. The bottom of the
detached haze layer is a few hundred kilometers above the surface
and is about 120 kilometers (75 miles) thick, consistent with
Voyager findings 23 years ago.
The image was taken with the narrow angle camera on July 3, 2004,
from a distance of about 789,000 kilometers (491,000 miles) from
Titan and at a Sun-Titan-spacecraft, or phase, angle of 114
degrees. The image scale is 4.7 kilometers (2.9 miles) per pixel.
