| Sunrise over Saturn's uppermost ammonia-ice cloud deck. Colourful
halos from residual ammonia crystals surround the sun as foils to
the far more distant rings marching across the sky. The bright B ring's
innermost edge is ~18,700 miles above, beneath it is the faint and
tenuous C or 'crepe' ring. The moon at top is Tethys.
The painting by meteorologist and artist Jacob
Klee is for latitude 26°N Longitude 120°W 1200UT on
March 18, 2016.
©2002 Jacob Klee, reproduced with permission.
like Jupiter, is thought to have three main cloud layers. They lie
much deeper down in its atmosphere with the pressure already 0.5-1
bar at the uppermost ammonia-ice crystal haze and cirrus layer. An
intermediate level of ammonium hydrosulfide is 60 km (37 miles) below
that. Water-ice and water droplet clouds are yet another 90 km deeper.
Titan, Saturn's largest moon, could also be a halo candidate. Models
of its hazy atmosphere predict methane-ice clouds at its tropopause
40 km above the surface where the temperature is about 73 K
More about its atmosphere should be learned when the European Huygens
probe descends through it in December 2004.
Circular halos produced by three crystal forms of ammonia (top) and