NASA's Mars Orbiters have for the first time revealed a seasonal dust storm pattern on the Red Planet -- paving the way to improve the scientists' ability to predict the potentially hazardous phenomena for future robotic and human missions to the planet.After decades of research focusing mainly on images to understand the seasonal patterns of Martian dust storms, the clearest pattern emerged after an analysis of the Red Planet's atmospheric temperature.
"When we look at the temperature structure instead of the visible dust, we finally see some regularity in the large dust storms," said lead study author David Kass of NASA's Jet Propulsion Laboratory in California.According to the study, published recently in the journal Geophysical Research Letters, temperature records from NASA Mars orbiters reveal a pattern of three types of large regional dust storms occurring in sequence at about the same time each year during the southern hemisphere spring and summer. Each Martian year lasts about two Earth years."Recognising a pattern in the occurrence of regional dust storms is a step toward understanding the fundamental atmospheric properties controlling them," Kass said. "We still have much to learn, but this gives us a valuable opening," he added.
The NASA researchers used data from the Mars Climate Sounder on Mars Reconnaissance Orbiter and the Thermal Emission Spectrometer on Mars Global Surveyor to analyse temperature data of a broad layer about 25 km above the Martian surface.Most Martian dust storms are localised, smaller than about 2,000 km across and dissipating within a few days. Some become regional, affecting up to a third of the planet and persisting up to three weeks. Three large regional storms, dubbed types 'A', 'B' and 'C', appeared in each of the six Martian years investigated.Multiple small storms form sequentially near Mars' north pole in the northern autumn, similar to Earth's cold-season arctic storms that swing one after another across North America."On Mars, some of these break off and head farther south along favoured tracks," Kass said. "If they cross into the southern hemisphere, where it is mid-spring, they get warmer and can explode into the much larger Type A dust storms," he added.