Orbit-spin coupling and the interannual variability of global-scale dust storm occurrence on Mars. (May 2017)

• Record Type: Journal Article
• Authors: Shirley, James H.; Mischna, Michael A.
• Is Part Of: Planetary and space science. Volume 139(2017)
• Page Start: 37
• Page End: 50
• Publication Date: 2017-05
• Subjects: Mars -- Mars atmosphere -- Orbit-spin coupling -- Mars dust storms -- Mars dust cycle -- Atmospheric interannual variability; Space sciences -- Periodicals; Atmosphere, Upper -- Periodicals; Sciences spatiales -- Périodiques; Haute atmosphère -- Périodiques; 523
• DOI: 10.1016/j.pss.2017.01.001
• Languages: English
• ISSNs: 0032-0633

Abstract

Abstract: A new physical hypothesis predicts that a weak coupling of the orbital and rotational motions of extended bodies may give rise to a modulation of circulatory flows within their atmospheres. Driven cycles of intensification and relaxation of large-scale circulatory flows are predicted, with the phasing of these changes linked directly to the rate of change of the orbital angular momentum, dL /dt, with respect to inertial frames. We test the hypothesis that global-scale dust storms (GDS) on Mars may occur when periods of circulatory intensification (associated with positive and negative extrema of the dL /dt waveform) coincide with the southern summer dust storm season on Mars. The orbit-spin coupling hypothesis additionally predicts that the intervening 'transitional' periods, which are characterized by the disappearance and subsequent sign change of dL /dt, may be unfavorable for the occurrence of GDS, when they occur during the southern summer dust storm season. These hypotheses are strongly supported by comparisons between calculated dynamical time series of dL /dt and historic observations. All of the nine known global-scale dust storms on Mars took place during Mars years when circulatory intensification during the dust storm season is 'retrodicted' under the orbit-spin coupling hypothesis. None of the historic global-scale dust storms of our catalog occurred during transitional intervals. Orbit-spin coupling appears to play an important role in the excitation of the interannual variability of the atmospheric circulation of Mars. Highlights: We test the hypothesis of a weak coupling of the orbit and spin motions of Mars. The Mars atmosphere may play an active role in the coupling. Quasi-periodic cycles of circulatory intensification are 'retrodicted'. Orbit-spin coupling may explain the intermittency of global dust storms on Mars.