Surface Conditions (Long Term)
This figure shows temperature measured by the Pathfinder ASI/MET instrument, 1.0 m above the level of the lander solar panels, for a period of continuous measurement during Sols 68 and 69. Measurements are obtained every 4 seconds. Temperature is given in Kelvin, and time is expressed in Sols, where 68.0 is midnight at the end of Sol 68 and 68.5 is noon on Sol 69. Coverage extends from roughly 9 am on Sol 68 to 2:30 p.m. on Sol 69. Temperatures fall from a maximum of 265 K at about 2:30 p.m. to a minimum of 196 K just before dawn at 5:30 am. During the morning and afternoon, surface heating causes turbulent convection, and temperatures fluctuate rapidly by as much as 15-20 K. At sunset and sunrise the atmosphere is stable, and temperatures vary by significantly less than 1 K in the short term. During the night, the atmosphere is also stable with cold air near the surface, but is disturbed frequently by downslope winds which produce short-term temperature fluctuations of a few degrees.
This figure shows pressure measured by the ASI/MET instrument during the period covered by the temperature figure described above. Both diurnal (daily), semidiurnal (twice-daily), and higher order variations can be seen clearly. Peak-to-peak variations are approximately 0.3 mbar, or 5% of the mean pressure. The daily pressure minimum occurs at sunset and the maximum is usually found shortly after sunrise. Narrow pressure minima, produced by 'dust devils', can be seen at Sols 67.486, 67.560, and 68.535.