Meteorological results from the surface of Mars: Viking 1 and 2

Abstract

We deal here primarily with the surface meteorological data for both Viking landers during the nominal missions (44 sols for lander 1 and 61 sols for lander 2). The diurnal patterns of wind, temperature, and pressure were strongly similar from sol to sol, as was expected in the summer. The chief characteristics of the wind data are that winds were light (a few meters per second), with a complex hodograph at VL‐1 dominated by counterclockwise turning of the wind and a simpler hodograph at VL‐2 marked by clockwise turning of the wind. This repetitive pattern of wind has begun to break down at VL‐2 with advancing season, and several episodes of protracted northeasterly winds have occurred. Some of these are associated with lower than normal temperatures. Examples are given of wind and temperature traces over short periods, illustrating the effects of convection, static stability, and lander interference. We present a theoretical argument based upon the horizontal scale dictated by heating of slopes and upon vertical mixing of momentum to explain the different sense of rotation of the wind vectors at the two sites. Analysis of the semidiurnal pressure oscillation suggests that absorption of solar radiation is an important thermal drive but that convective heat flux from the surface is also significant. The seasonal variation of pressure extending past the end of the nominal missions shows a decrease of pressure to a minimum at Ls ≈ 149° with a rapid rise thereafter. This is clearly due to condensation and sublimation of CO2 on and from the southern polar cap.

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

“…After several failures, the first successful meteorological observations from the Martian surface were made in 1976 by the two Viking landers (Chamberlain et al 1976;Hess et al 1977;Tillman et al 1994). The main goals of these meteorological observations were to study meso-scale and planetary-scale systems and processes, to investigate boundary layer phenomena and to obtain a better understanding of the Earth's atmosphere through comparison with that of Mars.…”

“…From this sol onward, a VL2 engineering sensor was used for making temperature measurements, with a worst-case reduced accuracy of ±4°C (Hess et al 1977;Sutton et al 1978). Problems with VMIS onboard VL1 started on sol 45 when the heater of the wind direction sensor failed.…”

“…In addition, operational modes consisting of extended periods of sampling at 1 Hz were used. Initially, four pressure measurements at 1 Hz were made at the start of every module, but this was later reduced to one sample every 17 min (Hess et al 1977). The data acquisition frequency was reduced towards the end of the landers' lives.…”

Utopia Basin, Mars: Characterization of topography and morphology and assessment of the origin and evolution of basin internal structure

“…The images returned by Mariner 9 of the massive outflow channels provided the first indication that large amounts of water once flowed across the surface of Mars [McCauley et al, 1972;Masursky, 1973;Milton, 1973], despite the fact that at current pressures and temperatures liquid water is not stable on the surface [Hess et al, 1977;Kieffer et al, 1977]. While most investigators agree that fluvial processes have operated at some time during Martian history [e.g., Sharp and Malin, 1975;Cart, 1979Cart, , 1996Baker, 1982 Utopia Planitia is a large plain located in the northern lowlands of Mars (Plate 1 a).…”

Assessing the Martian surface distribution of aeolian sand using a Mars general circulation model

“…The lack of small-scale topographic variability allows the MGCM to represent wind stress as an instantaneous value over 1.5 hours without losing any largescale wind stress fidelity. However, short time period, small scale temporal and spatial gusts may be responsible for transporting a greater amount of sand than predicted; the mean winds measured at Viking Lander I on sol 22 were 2.64 m/s, yet periodic 6-8 m/s gusts were observed [Hess et al, 1977]. Lastly, we use the wind stresses calculated at the lowest level of cells in the MGCM, a height -250 m above the surface, even though this is more than ideal for a surface representation.…”