“Watch out for brilliant white clouds that collect around the Tharsis volcanoes”
Summer in the Martian southern hemisphere causes the southern polar cap (the white area at the top of this south-up view) to shrink, while large clouds form in the atmosphere
Below top: the location of Olympus Mons is revealed to Earthbound observers by the clouds around its summit Bottom: clouds are also known to gather in the huge Hellas Basin to the south of the triangular Syrtis Major
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volcanoes. Olympus Mons in particular can attract bright clouds; these indicate its position in small to medium telescopes – the Solar System’s largest volcano is otherwise invisible to such apertures.
Bright clouds and fogs also collect in the deep basins; in January keep an eye on the Hellas Basin, to the south of Syrtis Major. It is not uncommon for
Visual filters are a great help when observing Mars – most telescopes come with a set and they are very easy to use. You simply screw them into the thread at the base of your eyepiece. Each filter is unique, and you can identify each one by looking at the W number on the side; this gives the filter’s ‘Wratten number’. If you have a small to medium sized telescope, try using a light blue filter (W80 or W80A) to increase the definition of white clouds. > < Colourful views: Wratten filters make Martian dust clouds easier to see than in an unfiltered view (top left). Use light blue (W80A), yellow (W15) or violet (W47) filters to enhance cloud definition
Hellas to become filled with white clouds when it’s near the morning or evening limb and as a result, it can become very bright. Eridania, Electris and Chryse are regions also prone to attracting clouds.
Filter familiarity
If you do see fogs and white clouds, it is worth spending some time observing them as they can be quite dynamic, often forming and evaporating over the course of an hour or two. It is particularly satisfying to watch bright clouds which have collected in the early morning chill of the Hellas Basin, slowly disperse during the course of an observing session.
When bright clouds occur on the limb of the planet, they can be really quite brilliant. If you have a larger telescope, a W47 violet filter will help bring fine details out further. A W15 yellow filter will make the southern > polar cap slightly easier to see, as it is now quite small and a challenge in small telescopes.
By January it is spring in the northern hemisphere and the vast north polar hood is extending quite a way south. You should be able to glimpse it as a bluishwhite haze on the northern limb, and it will become more prominent towards the year’s end. Mars’s tilt will also start to change – from January onwards, the northern hemisphere will gradually be better placed for views of well-known albedo features like Acidalium and Elysium. By March, observers using larger scopes might be able to catch sight of the northern polar cap.