Gusev Crater, Mars: Observations of three dust devil seasons

Abstract

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.