Gusev Crater, Mars: Observations of three dust devil seasons

Abstract

[1] Spirit began operations in Gusev Crater in January 2004 and has returned data on three seasons of dust devil (DD) activity. Total DDs observed were 533 in season one, 101 in season two, and 127 in season three. Their general characteristics are the same within factors of 2 among the seasons, with median diameters of 19 m in season one, 24 m in season two, and 39 m in season three, and dust flux values for individual vortices ranging from 4.0 × 10 −9 to 4.6 × 10 −4 kg m −2 s −1 in season one, 5.2 × 10 −7 to 6.2 × 10 −5 kg m −2 s −1 in season two, and 1.5 × 10 −7 to 1.6 × 10 −4 kg m −2 s −1 in season three. All three seasons were initiated with the onset of southern Martian spring within 14 sols of the same L s (181°) and their frequency increased to the period corresponding to late southern spring. The occurrences decreased monotonically in seasons one and three but apparently ended abruptly in season two when a large dust storm occurred; although the dusty atmosphere might have precluded the detection of active DDs, the abrupt cessation could result from conditions such as thermal stability of the atmosphere due to the presence of dust which could halt DD formation. Dust devils can contribute significant quantities of dust to the atmosphere, although it is unclear as to whether this dust stays locally or is injected into higher-altitude winds and is distributed elsewhere. In the three DD seasons observed through Spirit, DDs in Gusev Crater injected a minimum average of ∼18 × 10 6 kg of material into the atmosphere each season.

The Modern Near-Surface Martian Climate: A Review of In-situ Meteorological Data from Viking to Curiosity

“…2, left column). Differences in solar insolation between the perihelion and aphelion seasons produce on average higher temperatures during the perihelion season, enhancing the injection of dust into the atmosphere via wind stress and dust devils (Haberle et al 1982;Newman et al 2002aNewman et al , 2002bKahre et al 2006;Greeley et al 2010). Satellite measurements of atmospheric opacity show similar aphelion-versus-perihelion behavior on a planet-wide scale (Smith 2004;Cantor et al 2001;Montabone et al 2015).…”

Dust Devil Sediment Transport: From Lab to Field to Global Impact

“…On Mars, the images taken by the MER Spirit rover are again the only statistically significant data set (Greeley et al , 2010. During the first full dust devil season (i.e., southern spring and summer) of Spirit operations, there were 51 dust devils km −2 sol −1 in Gusev crater .…”

“…Inter-annual differences in dust devil frequency are attributed to variations in atmospheric opacity due to regional dust storms that change the local thermodynamic conditions, with increased atmospheric dust content tending to reduce e.g. the surface sensible heat flux and thus reduce the number of dust devils present (Greeley et al 2010;.…”

“…About 40% of the total had obscuration of 1% or more (indicating a line-of-sight opacity of ∼ 0.01) and about 10% had 5% obscuration or more. While large pressure drops (indicating close distances and/or intense vortices) could have large or small obscuration, it was noticed that large obscuration was only found with the more intense Rover Spirit (Greeley et al , 2010. Over three martian years the cameras onboard Spirit routinely imaged dust devils on the floor of Gusev crater The obtained dust concentrations varied from 2.1 × 10 −9 − 2.5 × 10 −4 kg m −3 .…”

“…The result was that the distribution of vertical speeds ranged from 0.04 to 17.0 m s −1 . From these observations Greeley et al (2010) calculated that the vertical dust flux for individual vortices ranged from 4.0 × 10 −9 − 1.6 × 10 −4 kg m −2 s −1 .…”