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  • Dust in the Year Before Curiosity

    This project closed in late 2015. But work on Martian dust continues…

    The Mars Year before the landing of the Mars Science Laboratory Curiosity was a year of excellent observational coverage by the Mars Climate Sounder on NASA’s Mars Reconnaissance Orbiter as the result of quiet weather and good instrument and spacecraft health. Focusing on changes in the dust distribution during this year can provide insight into the dynamical and/or observational origins of the detached dust layers that are ubiquitous in the tropics and are occasionally observed elsewhere on the planet.

    An HU-led team (including Dr. Nicholas G. Heavens and CURE student Morgan S. Johnson) closely studied detached dust layers during this Mars Year.

    Change in dust (left panels) and water ice (right panels) mass mixing ratio between night and day on Mars. Dust is being continuously injected above the planetary boundary layer on Mars during the day, a sign of intense convection near the Equator during the entirety of the year.

    Change in dust (left panels) and water ice (right panels) mass mixing ratio between night and day on Mars. Dust is being continuously injected above the planetary boundary layer on Mars during the day, a sign of intense convection near the Equator during the entirety of the year. (Click image for larger version).

    By taking advantage of Mars Climate Sounder’s observational pattern, the team sampled change in Mars’s atmosphere in the same place at twelve hour intervals. The results were striking. Throughout the year, a dust layer at the Equator significantly thickens during the day (see Figure) and thins at night. This diurnal variability is much stronger in the first half of Mars’s year than the second half. Diurnal variability is also stronger near Mars’s Tharsis volcanoes. Both of these results suggest that Mars’s tropical atmosphere frequently contains updrafts that are being rapidly transporting dust 15-30 km above Mars’s surface. At night, however, some process, probably related to water ice clouds, can rapidly remove dust from the atmosphere. Another surprise is that detached dust layers are primarily focused north of the Equator throughout the year and do not follow the motions of Mars’s Hadley cell, as would be expected by analogy with tropical convection on the Earth.

    This work was published in August 2014 in the Journal of Geophysical Research Planets .

    In the subsequent year of work, Dr. Heavens investigated unusual detached dust layers near some of Mars’s largest volcanoes. The existence of these layers suggests that volcano-based dust storms on Mars transport dust and water vapor much higher in the atmosphere than previously suspected. In one case, a storm was directly observed that stretched as high as 50 km (30 miles) above the summit of the Martian volcano, Arsia Mons.

    In addition, the haze layers are rarely observed when dust storms are observed on the volcanoes. This observation suggests that dust storms are short-lived, form late in the morning or early in the afternoon, and therefore are more common than previously suspected.

    Mars Climate Sounder observations of emission from dust layers over the Martian volcano, Arsia Mons. The black crosses indicate retrieved amounts of dust are higher than 50 ppm.

    Mars Climate Sounder observations of emission from dust layers over the Martian volcano, Arsia Mons. The black crosses indicate retrieved amounts of dust are higher than 50 ppm. The black line shows the location of the Martian surface. (Click image for larger version)

    This work was published in Geophysical Research Letters  and covered by New Scientist.

    This project was supported by NASA’s Jet Propulsion Laboratory, California Institute of Technology under subcontract 1471216 to Hampton University. Some of the second year of work was supported by NASA’s Mars Data Analysis Program (NNX14AM32G).

    The views expressed on this page represent the views of the investigators alone and do not represent the views of JPL or NASA.