Topography of the Northern Hemisphere of Mars from the Mars Orbiter Laser Altimeter

Abstract

The first 18 tracks of laser altimeter data across the northern hemisphere of Mars from the Mars Global Surveyor spacecraft show that the planet at latitudes north of 50°is exceptionally flat; slopes and surface roughness increase toward the equator. The polar layered terrain appears to be a thick ice-rich formation with a non-equilibrium planform indicative of ablation near the periphery. Slope relations suggest that the northern Tharsis province was uplifted in the past. A profile across Ares Vallis channel suggests that the discharge through the channel was much greater than previously estimated. The martian atmosphere shows significant 1-micrometer atmospheric opacities, particularly in lowlying areas such as Valles Marineris.

Hydraulic modelling of Athabasca Vallis, Mars

“…Carr, 1979;Baker & O'Connor, 1988;Komatsu & Baker, 1997;Smith et al, 1998). The Athabasca channel palaeoflood estimates presented here benefit from three improvements over previous efforts: a more recent hydraulic model, more accurate topography, and better geological constraints on palaeoflood height.…”

“…For Athabasca Vallis, these cross sections were taken from a digital elevation model of Mars Orbiter Laser Altimeter (MOLA) data (Zuber et al, 1992;Smith et al, 1998). MOLA takes a topographic measurement every ~300 m along track.…”

“…Constraining the amount of floodwater previously on the surface of Mars is an important contribution to this strategy. Ares Vallis, one of the largest Martian outflow channels which debouche into Chryse Planitia, measures on the order of 100 km wide, 1300 m deep, and 1500 km long (Komatsu & Baker, 1997;Smith et al, 1998). These circum-Chryse channels have been dated by counting the number and sizes of craters on the channel floors at more than ~2 Ga.…”

Geological Processes and Evolution

“…Subsequently, data from the Viking Orbiters (Carr et al, 1977b) allowed mapping and characterization of the extent, timing, and styles of volcanism on Mars (Figure 1; Greeley andSpudis, 1978, 1981;Mouginis-Mark et al, 1992;Greeley et al, 2000). High resolution images (Malin et al, 1998) (Figure 1), information on surface compositions (McSween et al, 1998), and topographic data (Smith et al, 1998(Smith et al, , 1999a from the Mars Global Surveyor (MGS) permit comparison of Martian volcanism with theoretical analysis of the ascent and eruption of magma on Mars (e.g., Wilson and Head, 1994).…”

New views of Mars eolian activity, materials, and surface properties: Three vignettes from the Mars Global Surveyor Mars Orbiter Camera

“…At the contact between the south wall and floor, there are wind-eroded ridges that are up to 120 m high; the surfaces adjacent to the ridges include dark drifts or dunes ("d" in Figure 14b). At the same time that image AB1-03001 was taken, the Mars Orbiter Laser Altimeter (MOLA) obtained a topographic profile [Smith et al, 1998] that shows the maximum slope on the generally concave south crater wall is about 33 ø (Figure 16). This wall is completely covered by a smooth-surfaced, dark deposit that reaches nearly to the crater rim.…”