FIGURE 1. Examples of spots and fans in the south polar region of Mars.

From the following article:

CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap

Hugh H. Kieffer, Philip R. Christensen and Timothy N. Titus

Nature 442, 793-796(17 August 2006)



a, MOC image E09-00231 at Ls 248° is approx3 km times 5 km in size, centred near 85.2° S and 181.4° E at approx3 m per pixel. b, MOC image E07-00159 at Ls 207° is approx3 km times 6 km in size centred near 86.3° S and 94.4° E at approx11 m per pixel. The dark fans are typically tens to hundreds of metres in length, 10–30° in angular size, originate from a dark spot, and point in a similar direction within a given area, sometimes with curvilinear trends influenced by topographic slopes. Occasionally fans form in multiple directions from a single spot. Some multiple fans have one diffuse edge, suggesting subsequent transport at an angle to the initial orientation. Fans are typically dark relative to the surrounding surface, although relatively bright fans also occur.