This is an example of the importance of ground-based observations of the Solar System. Another feature that is of great interest to professional Mars researchers is the Trivium Cerberus, on the southern rim of the Elysium shield. Troiani et al. The Martian atmosphere is ever- changing. White water ice clouds, yellowish dust clouds, bluish limb hazes, and bright surface frosts have been studied with increasing interest in the past two decades.
Clouds seem to be related to the seasonal sublimation and condensation of polar-cap material.
An intensive study of Martian meteorology has been conducted by the ALPO Mars Section using visual data and photographs from professionals and amateurs around the world. This study has now been expanded to include 24,130 observations between 1965 and 1993. Statistical analysis indicates that discrete water ice crystal cloud activity and near-surface fogs occurrence is significantly higher in the spring and summer of the Martian Northern Hemisphere than the same seasons for the Southern Hemisphere. For inclusion in this unique study, it is essential that ALPO astronomers employ blue filters when making visual, photographic, or CCD observations. Although often observed without filters, they are best seen in blue or violet light when they are high in altitude and in yellow or green light at very low altitudes.