It gives a whole new meaning to "unsettled" weather. The bizarre winds that plague the surface of Mars and would make the life of a Martian weather forecaster practically impossible have been revealed by Nasa's Pathfinder probe.
Analysis of data recovered by a meteorological sensor on the lander in 1997, and announced at the American Astronomical Society's planetary sciences meeting in Padua, Italy on Monday, revealed the irritating, though not life threatening, weather any astronauts venturing to the red planet in future may have to face.
The winds are in part powered by the great temperature swings between night and day - between -73°C and -13°C. Turbulent convection currents during the day mean the temperature at any point can shift by six degrees in a matter of 20 seconds, while the wind can switch from south to northeast to southeast over a two-minute period. In this time, the magnitude of the wind can alter by several miles per hour.
"If we were standing there, we would feel alternating draughts of noticeably warmer and cooler air, changing as often as three times a minute," said Alan Seiff, of Nasa's Ames Research Center in California.
At sundown, this rapid fluctuation simply stops. But after several hours of calm, the winds begin to pick up again to peak at 2am at about 11mph, dying away once more before sunrise starts the unsettled weather again.
During the time the instrument monitored the weather, this cycle broke down only once, when what appeared to be a weather front passed over the probe, bringing with it a late morning storm with the wind gusting up to 40mph.
However, the very low atmospheric pressure on Mars - about 0.7 per cent of that on Earth - means these winds pose little threat to any future manned missions to the planet.
"It is interesting to speculate on how these winds will affect humans when manned missions are undertaken," said Dr Seiff. "The largest gust of wind we have detected thus far would only exert a force on a man of about half a pound, but the wind may also contain fine dust that would impinge on the suits humans would have to wear and could be unpleasant."