Late Winter/Early Spring.

When the Sun first rises over the polar cap after the frozen hell of midwinter, a sparkling vista of clean white frost is revealed. Everything is buried by 0.5-1 metre of crisp CO2 snow and ice, at a temperature of -125 C. A tiny proportion of H2O ice also exists in the seasonal polecap, but this is less than 1/10 of 1% by volume(i.e. less than 1 mm thick).

Everything is buried by this coating of frost. The gully morphologies are picked out by the sunlight shining at a low angle across the surface. All shades of grey in the image are caused by slope of the ground and shading, rather than by intrinsic colour differences, with one exception - some fuzzy dark spots represent location where the snow is beginning to melt through and become thin, and the darker ground beneath is showing through

Note that there is no trace of the dark streaks down the channel centres. One would expect these to be buried by the snowpack and to gradually emerge as the snow thaws. At this time of year, they are well buried by the (presumably) thicker snow in the sheltered alcoves and channel cores.

      Created: May 2002
      Last modified: May 2002
      Authorised by:  Head, Earth Sciences

      Maintained by: Nick Hoffman
      Email: nhoffman@unimelb.edu.au