Here you will read some commentaries about my observations about Mars in 1999:
  From 13 April until now, I saw clouds and clouds:   The Blue Syrtis Cloud was very evident. I saw it as a blue haze, even though without a blue filter. When the Blue Syrtis Cloud was seen in the center of the planetary disc, the Syrtis Major was faint and more bright. After now, I never saw the Blue Syrtis Cloud so evident.
  Orographic clouds very bright was seen over Elysium, all days. Over Tharsis volcanoes the clouds were less bright than in 1997 Apparition, but they were bright for to be seen even without filters. Alba Patera was more brilliant than the volcanoes of Tharsis ridge (Ascraeus, Pavonis and Arsia). I could see the "cotton balls" over Olympus Mons and Alba Patera.
  Blue veil was seen covering big areas, mainly Tharsis. Between LCM=120°W and 100°W, I saw the south regions with bluish color, even though without filters.
  Like Hellas, Argyre was covered by frost. I saw a white smudge over Argyre with photometric around 05 (NPC=0), on 4 May. The Hellas Basin was very brilliant (bright as a Polar Cap) in April, but your glisten waned on end of May. Hellas was better visible across a green filter. We observers, account that if the image of a bright smudge is better visible across a green filter, we think in frost. But perhaps, the frost that covered the floor of Hellas, disperses actually, doing your brilliance to reduce.
  Thank you for all.