NASA’s Mars orbiters discover seasonal dust storm pattern
After decades of trying to determine patterns in Martian dust storms from images showing the dust, a team of researchers has found that the clearest pattern can be discerned by measuring the temperature of the Martian atmosphere. Using data gathered by NASA orbiters during three recent Martian years, the scientists found a pattern of three types of large regional dust storms that occur in the same sequence each year during spring and summer in the southern hemisphere of Mars.
“When we look at the temperature structure instead of the visible dust, we finally see some regularity in the large dust storms,” said David Kass of NASA’s Jet Propulsion Laboratory, Pasadena, California. He is the instrument scientist for the Mars Climate Sounder on NASA’s Mars Reconnaissance Orbiter and lead author of a report about these findings posted this week by the journal Geophysical Research Letters.
Scientists have been studying how dust moves across the surface of Mars during the Martian year (which measures about 1.88 years here on Earth).
“Recognizing a pattern in the occurrence of regional dust storms is a step toward understanding the fundamental atmospheric properties controlling them,” Kass added. “We still have much to learn, but this gives us a valuable opening.”
Dust lifted by Martian winds is linked directly to the atmospheric temperatures. The dust absorbs sunlight, so the Sun heats dusty air more than clear air. This effect can be quite dramatic, with a difference of over 63 Fahrenheit degrees (35 degrees Celsius) between dusty and clean air. This heating also impacts the global wind distribution, which can produce downward motion that warms the air outside the regions heated by dust. As a result, temperature observations can capture both direct and indirect effects of dust storms on the Martian atmosphere.
NASA has been operating orbiters around Mars continuously since 1997. The Mars Climate sounder on the Mars Reconnaissance Orbiter and the Thermal Emission Spectrophotometer on the Mars Global Surveyor, which studied Mars from 1997 to 2006, both used infrared observations to measure atmospheric temperature. Kass and his fellow researchers analyzed temperature data representative of a broad layer centered about 16 miles (25 kilometers) above the Martian surface. At this height, the atmosphere was more likely to be influenced by large regional storms than small local storms.
Improving the ability to predict large and potentially hazardous dust storms on Mars would have safety benefits for both robotic and crewed missions to the planet’s surface. By recognizing patterns and categories of dust storms scientists will gain an increased understanding of how seasonal local events affect global weather on an average Mars year. The longevity of NASA’s MRO mission has helped to enable a number of different studies on the seasonal patterns on Mars.
In addition to studying the Martian atmosphere and climate, the MRO spacecraft has also mapped out areas of interest for NASA’s rovers on the planet’s surface. One such area is “Marathon Valley”, a region of water-related clays that slices through the rim of Endeavour Crater. The area has provided a number of research targets since NASA’ Opportunity rover arrived there in July 2015. Researchers named the area Marathon Valley because Opportunity’s arrival at this part of the rim coincided with the rover surpassing marathon-footrace distance (26.219 miles or 42.195 kilometers) in total driving distance since its 2004 arrival on Mars. The rover is now preparing to move on to a new location.
“We are wrapping up our last few activities in Marathon Valley and before long we’ll drive away, exiting along the southern wall of the valley and heading southeast,” said Opportunity Principal Investigator Steve Squyres, of Cornell University, Ithaca, New York.
As the rover examined the clay-bearing rocks on the valley floor that MRO detected from orbit, Curiosity discovered streaks of reddish, crumbly material of the valley’s southern flank. The science team initially planned to use the rover’s Rock Abrasion Tool (RAT) to grind away the surface of the rock to expose the interior for inspection.
“What we usually do to investigate material that’s captured our interest is [finding] a bedrock exposure of it and [using] the RAT,” Squyres said. “What we didn’t realize until we took a close-enough look is that this stuff has been so pervasively altered, it’s not bedrock. There’s no solid bedrock you could grind with the RAT.”
Instead, the rover used one of its wheels to scuff some of the material to expose fresh surfaces.
“In the scuff, we found one of the highest sulfur contents [that have] been seen anywhere on Mars. There’s strong evidence that, among other things, these altered zones have a lot of magnesium sulfate. We don’t think these altered zones are where the clay is, but magnesium sulfate is something you would expect to find precipitating from water,” Squyres added. “Fractures running through the bedrock, forming conduits through which water could flow and transport soluble materials, could alter the rock and create the pattern of red zones that we see.”
Opportunity has driven 26.59 miles (42.79 kilometers) as of June 14. The rover holds the record for greatest distance driven on a planetary body other than Earth.
Video courtesy of NASA/JPL-Caltech
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.