The yellow line on this graphic indicates the number of hours of sunlight each sol, or Martian day, at the Phoenix landing site's far-northern latitude, beginning with the entire Martian day (about 24 hours and 40 minutes) for the first 90 sols, then declining to no sunlight by about sol 300. The blue tick mark indicates that on Sol 124 (Sept. 29, 2008), the sun is above the horizon for about 20 hours.
The brown vertical bar represents the period from Nov. 18 to Dec. 24, 2008, around the "solar conjunction," when the sun is close to the line between Mars and Earth, affecting communications.
The green vertical rectangle represents the period from February to November 2009 when the Phoenix lander is expected to be encased in carbon-dioxide ice.
Image NASA/JPL-Caltech/University of Arizona/Lockheed Martin