ARES VALLIS, MARS—With temperatures around −9°C in the mid-afternoon and down to −75°C at night, northern summer at the Mars Pathfinder landing site is nearing its close. Autumn will begin in about 2 weeks, right about the same time that Pathfinder's orbiting companion, Mars Global Surveyor, will reach the Red Planet.
As autumn approaches, the average daily temperatures will continue to decrease, and there is some potential for the winds to pick up. In the 1970s, dust storm season was seen to extend from northern autumn right through winter. In the late 1970s and early 1980s, the Viking 1 lander (which is located about 800 km from Pathfinder) detected changes in atmospheric opacity (that is, how much dust is suspended in the atmosphere) from about the start of autumn and on into the winter. Will Pathfinder see the same? Will strong winds blow through the site and rub out the tire tracks left by the 62-cm long rover, Sojourner?