Philip B. James

Martian south polar cap boundary: 1971 and 1973 data

Abstract International Planetary Patrol photographs of Mars obtained during the 1971 and 1973 apparitions have been used to produce regression curves for the Martian south polar cap for those years. Useful data span the range in areocentric longitude L s = 186−261° in 1971 and L s = 255−301° in 1973. These regression curves are compared to the 1977 regression curve obtained from Viking observations and to the results of 1956 observations. There is remarkable consistency between the 1971 IPP and 1977 Viking data points, and the 1973 regression does not appear to have differed significantly from those of 1971 or 1977.

Recession of Martian north polar cap: 1979–1980 Viking observations

Abstract The 1979–1980 regression curve for the north polar cap of Mars, determined from Viking orbiter images, is compared to Viking observations of the same season 1 (Martin) year earlier and to telescopic observations. Differences between the two years cannot unambigously be attributed to dynamical effects because of uncertainties introduced by limited longitudinal coverage.

Interannual variability of Mars' south polar cap

Abstract Telescopic data on the twentieth-century regressions of Mars south polar cap have been reexamined for evidence of interannual variability. Several regressions, particularly that of 1956, are found to differ significantly from the mean. The possibility of correlations with major dust storms is explored.

Martian north polar cap and circumpolar clouds: 1975–1980 telescopic observations

Abstract International Planetary Patrol pictures from 1975–1980 have been used to derive partial regression curves for Mars north polar cap during the 3 Martian years included in the study. The results confirm the existence of a surface cap during late winter and early spring which extends to at least 55°N lat and the mid-spring plateau in cap recession noted by previous studies. Comparison of images acquired using different filters reveals that a substantial increase in circumpolar clouds accompanies the resumption of cap sublimation at the end of the plateau period.

The Martian hydrologic cycle: effects of CO2 mass flux on global water distribution

Abstract The Martian CO2 cycle, which includes the seasonal condensation and subsequent sublimation of up to 30% of the planets atmosphere, produces meridional winds due to the consequent mass flux of CO2. These winds currently display strong seasonal and hemispheric asymmetries due to the large asymmetries in the distribution of insolation on Mars. It is proposed that asymmetric meridional advection of water vapor on the planet due to these CO2 condensation winds is capable of explaining the observed dessication of Mars south polar region at the current time. A simple model for water vapor transport is used to verify this hypothesis and to speculate on the effects of changes in orbital parameters on the seasonal water cycle.

Some photometric properties of the Martian south polar cap region during the 1971 apparition

Abstract High-quality Earth-based photographs from the Lowell Observatory Planetary Research Center collection have been analyzed to derive some photometric parameters for the Martian south polar cap region during the 1971 apparition. The optical thickness of the atmosphere above the cap varied with wavelength from 0.35 ± 0.05 in red light to 0.58 ± 0.06 inuv light. The effective geometric albedo is calculated from the 30° phase data assuming isotropic scattering; it varies from 0.85 ± 0.04 (in red light) to 0.63 ± 0.05 (in uv light).

Martian cloud systems: Current knowledge and future observations

Abstract In this paper we summarise the current understanding of Martian condensate and dust clouds. The paper is particularly concerned with the spatial, temporal and seasonal characteristics of the clouds. The condensate clouds are composed of water and ice particles and occasionally CO 2 particles. Dust clouds are composed of material from the surface and redistributed over the planet through the weather systems. The apparent lack of annual reproductivity of these dust storms forms a major unresolved problem. We discuss in this paper the types of observations needed in future space missions, in particular the requirements for the NASA Mars Geochemical Climatology Orbiter Mission planned for the end of this decade.

Persistent dust cloud activity on Mars near Echus Chasma in 1978

Abstract Clouds were recorded by Viking cameras during five out of six observations over the same side canyon of Echus Chasma during a period of over 3 1 2 months in 1978. Although these clouds were different from one another in appearance, all were bright through a red filter and are believed to be at least partially composed of dust. Two of them were also imaged in violet light, in which they were also bright; therefore, they may also have contained condensate. A plausible explanation for the formation of the dust clouds is drainage winds, which are also known to be active to the west, in the Tharsis region during this season. In this case, winds may have been flowing downslope from the north rim of Tithonium Chasma.