The Mars Pathfinder Atmospheric Structure Investigation/Meteorology (ASI/MET) Experiment

Abstract

close to the observed value 29sin(ᐉ ϩ 241°) mas. 23. We thank the Mars Pathfinder project team for their enthusiasm and assistance in acquiring and understanding the tracking measurements; R. Wimberly for recovery of the Viking lander Doppler data; and J. Williams and an anonymous referee for helpful suggestions. The research described in this paper was carried out by the Jet Propulsion Laboratory, Califor- The Mars Pathfinder atmospheric structure investigation/meteorology (ASI/MET ) experiment measured the vertical density, pressure, and temperature structure of the martian atmosphere from the surface to 160 km, and monitored surface meteorology and climate for 83 sols (1 sol ϭ 1 martian day ϭ 24.7 hours). The atmospheric structure and the weather record are similar to those observed by the Viking 1 lander ( VL-1) at the same latitude, altitude, and season 21 years ago, but there are differences related to diurnal effects and the surface properties of the landing site. These include a cold nighttime upper atmosphere; atmospheric temperatures that are 10 to 12 degrees kelvin warmer near the surface; light slope-controlled winds; and dust devils, identified by their pressure, wind, and temperature signatures. The results are consistent with the warm, moderately dusty atmosphere seen by VL-1.The ASI/MET experiment consists of a suite of sensors designed to measure the vertical structure of the atmosphere during entry, descent, and landing (EDL) and to study martian surface meteorology and climate for the duration of the Pathfinder mission (1, 2). In situ vertical structure measurements were made only twice by the Viking entry vehicles (3), both during the daytime. In addition to adding a third profile, ASI/MET provides the first nighttime observation, giving information about the diurnal variation of vertical structure, particularly in the upper atmosphere, which is inaccessible to existing remote-sensing techniques. Both Viking landers obtained records of atmospheric pressure, temperature, and wind velocity at the surface that extended over several Mars years. More recent Earth-based, disk-averaged microwave observations have been interpreted to indicate episodic cooling of the martian lower atmosphere by about 20 K relative to the conditions observed during the Viking missions (4). By continuing the Viking record after 21 years, ASI/MET results are able to determine whether martian meteorology and climate have changed or remained stable in the late northern summer. Improved measurement sensitivity and temporal resolution (2) also reveal phenomena not seen by Viking and, together with temperature measurements at three levels, give better information on the exchange of heat and momentum between the atmosphere and the surface.

Comment on ''Observing desert dust devils with a pressure logger" by Lorenz (2012) – insights on measured pressure fluctuations from large-eddy simulations

“…The deepest pressure drops are predicted at the edges of convective cells (where strongest updrafts occur) and correspond to convective vortices (Michaels and Rafkin, 2004) which could form dust devils should surface dust be available to be lifted. Pressure drops associated with dust devils have been observed both on Earth (Renno et al, 2004;Lorenz, 2012) and Mars (Schofield et al, 1997;Ellehoj et al, 2010). In fact, the method by Lorenz (2012) is able to capture all convective vortices rather than only dust devils (i.e.…”

Electric and magnetic signatures of dust devils from the 2000–2001 MATADOR desert tests

“…Much like the observations of Martian dust devils by Viking [Ryan and Lucich, 1983], these terrestrial dust devils are found to possess ''hot cores'' with temperatures steadily rising and ultimately peaking in the dust devil center (Figure 6c). As with the Mars Pathfinder meteorology results [Schofield et al, 1997;Murphy and Nelli, 2002], a small but detectable pressure decrease (1-2 mb) occurs in the dust devil center. The observations of thermal and pressure gradients suggest the dust devil is a miniconvective system, with fluid cyclonic motion (winds) ultimately driven by near-ground thermal energy.…”

THEMIS VIS and IR observations of a high‐altitude Martian dust devil

“…[4] Tracks left by the passage of dust devils are found on nearly every region across the Martian surface [Cantor and Edgett, 2002], and nearly every orbiter and lander sent from Earth has directly observed active plumes, including: Viking Landers 1 & 2 (passage of vortex cores inferred by meteorological data) [Ringrose et al, 2003], Viking Orbiters 1 & 2 [Thomas and Gierasch, 1985], Mars Pathfinder Lander [Schofield et al, 1997;Metzger et al, 1999] and Mars Global Surveyor (MGS) [Edgett and Malin, 2000]. Measured diameters were between 28-509 m, with heights of 170 -8500 m. An extensive survey using 2 p.m. Mars Orbiter Camera (MOC) wide and narrow-angle images was conducted by Fisher et al [2005], who determined that Martian dust devils exhibit some regional and seasonal dependence with a bias toward northern latitudes during the warmest seasons.…”