[left]: The discovery image of the Martian polar storm as seen in blue light (410 nm). The storm is located near 65 deg. N latitude and 85 deg. W longitude, and is more than 1000 miles (1600 km) across. The residual north polar water ice cap is at top. A belt of clouds like that seen in previous telescopic observations during this Martian season can also be seen in the planet's equatorial regions and northern mid-latitudes, as well as in the southern polar regions. The volcano Ascraeus Mons can be seen as a dark spot poking above the cloud deck near the western (morning) limb; this extinct volcano towers nearly 16 miles (25 km) above the surrounding plains, and is about 250 miles (400 km) across.
[upper right]: Color polar view of the north polar region, showing the location of the storm relative to the classical bright and dark features in this area. The color composite data (410, 502, and 673 nm) indicate that the storm is fairly dust-free and therefore likely composed mostly of water ice clouds. The bright surface region beneath the eye of the storm can be seen clearly. This map covers the region north of 45 degrees latitude, and is oriented with 0 degrees longitude at the bottom.
[lower right]: Enhanced orthographic view of the storm centered on 65 deg. N latitude, 85 deg. W longitude. The image has been processed to bring out additional detail in the storm's spiral cloud structures.
The pictures were taken on April 27, 1999, with the NASA Hubble Space Telescope's Wide Field and Planetary Camera 2.
Credit: Jim Bell (Cornell U.), Steve Lee (U. Colorado), Mike Wolff (SSI), and NASA