NASA scientists have discovered that three powerful dust storms which occur each Martian year could pose a hazard to astronauts undertaking a mission to the Red Planet. The discovery also represents a rare opportunity forplanetary scientists to gain an insight regarding the processes atwork in the tenuous Martian atmosphere.
Dust storms on Mars areordinarily relatively small scale, short-lived affairs, measuring onaverage 1,200 miles (2,000 km) across, and observed to dissipatewithin a few days of forming. However, sometimes these weathersystems can evolve into larger regional storms, which have beenknown to last up to three weeks.
The largest of thesestorms can engulf most of the barren planet's southern hemisphere. Since NASA established its orbital presence around Mars in1997, two exceptionally powerful dust storms have succeeded in shrouding theentire planet.
The recent study, whichmade use of atmospheric temperature readings collected by NASA's Mars Reconnaissance Orbiter and the Mars Global Surveyor spacecraft, hasidentified storm patterns in Mars' annual weather cycle. Theresearch identifies three distinct storms that have been observed totake place on each of the last six Martian years.
Temperaturewas found to be the optimum means of tracking storm activity, asdust carried into the Martian atmosphere by the Red Planet's windsintercepts and absorbs the sunlight. By tracking the warmth signatureof the dusty air, which can be up to 63º F(35º C) warmer than its dust-free counterpart in a band 16miles (25 km) above the Martian surface, the researchers were able totrack the locations and intensity of the storms.
"Whenwe look at the temperature structure instead of the visible dust, wefinally see some regularity in the large dust storms," statesDavid Kass of NASA's Jet Propulsion Laboratory, Pasadena, California,and lead author of paper on the findings. "Recognizing a patternin the occurrence of regional dust storms is a step towardunderstanding the fundamental atmospheric properties controllingthem."
Each of the stormsappears around the same time, and forms in the same region eachMartian year. The first of the storms, imaginatively designated TypeA, originates as a smaller storm near the north pole during thenorthern autumn. As it travels south into the spring conditionsprevailing in the southern hemisphere, the winds are energized,lifting a greater amount of dust high into the Red Planet's atmosphere, allowing the storm to expandinto a regional weather event.
The Type B storminitially forms in the south polar region before travelling northprior to the onset of summer in the southern hemisphere. Multipleinstances of the storm could give rise to a wide spread haze. Thefinal storm – referred to as Type C – is the most unpredictable of thethree, varying significantly in power from year to year. Originatingin the northern hemisphere during the local winter, the storms sweep south,where they behave the same as Type A storms.
The ability to predictthese vast Martian weather events could have a significant impact onthe planning of future manned and unmanned exploration missions tothe Red Planet. Regional dust storms have the potential tosignificantly reduce the output of solar cells, such as thosecurrently powering the Curiosity and Opportunity rovers by coatingtheir sunlight collecting surfaces.
Furthermore, the electrostatic qualities of the storms could interfere with vital equipment, while the sheer density of the dust particles works to dramatically lower visibility for astronauts. The ability to plan around, or simply prepare for these weather events will allow for longer-lasting, safer missions to the Martian surface
Source: NASA
