2003 October 7

These nine unprocessed CCD images of Mars were taken at Leoncito, Argentina with the 0.60 metre Hogg telescope in the Johnson U band for 2.0 seconds each on the night of September 2 during moments of exceptional seeing. The Martian atmosphere is opaque at these wavelengths, so that no surface features are visible. The large black bands appearing at the bottom around the North Polar ca p, thus, are not surface features. They are zones in the atmosphere which are free of clouds. Likewise, the mottled appearances of these images across the equatorial regions are certainly due to variable cloud conditions across the planet's surface, which are largely a consequence of the sublimating South Polar cap. Close examination reveals clear movement of these atmospheric features with the planet's rotation, from right to left in these images. In all cases the images are inverted so that south is up.

The striking cloud features seen on the west limb of the planet (right side in the images) lie just north of a prominent feature called Solis Lacus at sunrise. The clouds are composed of carbon dioxide ice crystals at high altitude in the planet's thin atmosphere, and in these images it is easy to see them quickly dissipating as they were exposed to the morning sun light with the rotation of the planet.

The features seen at the two poles in these ultraviolet images are probably not surface ice as one might expect. More likely, they are extensive carbon dioxide clouds forming directly above the thin sublimating dry ice on the surface.

The images below the nine direct ones are isophotes of their corresponding images above.