Overview of the Mars Pathfinder Mission: Launch through landing, surface operations, data sets, and science results

Abstract

Abstract. Mars Pathfinder successfully landed at Ares Vailis on July 4, 1997, deployed and navigated a small rover about 100 m clockwise around the lander, and collected data from three science instruments and ten technology experiments. The mission operated for three months and returned 2.3 Gbits of data, including over 16,500 lander and 550 rover images, 16 chemical analyses of rocks and soil, and 8.5 million individual temperature, pressure and wind measurements. Pathfinder is the best known location on Mars, having been clearly identified with respect to other features on the surface by correlating five prominent horizon features and two small craters in lander images with those in high-resolution orbiter images and in inertial space from two-way ranging and Doppler tracking. Tracking of the lander has fixed the spin pole of Mars, determined the precession rate since Viking 20 years ago, and indicates a polar moment of inertia, which constrains a central metallic core to be between 1300 and -2000 km in radius. Dark rocks appear to be high in silica and geochemically similar to anorogenic andesites; lighter rocks are richer in sulfur and lower in silica, consistent with being coated with various amounts of dust. Rover and lander images show rocks with a variety of morphologies, fabrics and textures, suggesting a variety of rock types are present. Rounded pebbles and cobbles on the surface as well as rounded bumps and pits on some rocks indicate these rocks may be conglomerates (although other explanations are also possible), which almost definitely require liquid water to form and a warmer and wetter past. Airborne dust is composed of composite silicate particles with a small fraction of a highly magnetic mineral, interpreted to be most likely maghemite; explanations suggest iron was dissolved from crustal materials during an active hydrologic cycle with maghemite freeze dried onto silicate dust grains. Remote sensing data at a scale of a kilometer or greater and an Earth analog correctly predicted a rocky plain safe for landing and roving with a variety of rocks deposited by catstrophic floods, which are relatively dust free. The surface appears to have changed little since it formed billions of years ago, with the exception that eolian activity may have deflated the surface by -3-7 cm, sculpted wind tails, collected sand into dunes, and eroded ventifacts (fluted and grooved rocks). Pathfinder found a dusty lower atmosphere, early morning water ice clouds, and morning near-surface air temperatures that changed abruptly with time and height. Small scale vortices, interpreted to be dust devils, were observed repeatedly in the afternoon by the meteorology instruments and have been imaged.

Mineralogic and compositional properties of Martian soil and dust: Results from Mars Pathfinder

“…Details regarding observational planning and instrument sequencing can be found in the mission overview description by Golombek et al [1999]. Here, we briefly touch upon the most salient observational details relevant to the study of soils and dust at the landing site.…”

“…On Earth, numerous studies have demonstrated the link between soil physical and chemical properties and environmental conditions (e.g., reviews in the work by Schwertmann and Taylor [1989]; Cornell and Schwertmann [1996]); the working assumption is that similar inferences about environmental conditions on Mars. past and present, can be gleaned 1721 from measurements of the properties of soils found there todayAnalyses of remote sensing data specific to the Mars Pathfinder landing site both prior to and after landing revealed (1) that the site is in a region that is transitional between classical bright (Chryse) and dark (Acidalia) regions [Golombek et a!., 1997a], (2) that the lower albedo and Viking Orbiter red/blue ratio of the region appear to correspond to less bright dust at the Pathfinder site than Viking Lander 1 (VL1) [Golombek et al, 1997b], and (3) that the MPF site also has a greater abundance of dark materials. The dark materials at the MPF site could represent a contribution of "local" material [Larsen et a!., 1999], or could represent a contribution from dark soils not previously sampled by VL1 or VL2, neither of which landed in dark regions or found dark soil deposits at their landing sites.…”

chemical composition of martian soil and rocks: Complex mixing and sedimentary transport

“…A fundamental requirement of two component physical mixing models to explain chemical variation is that all interelement relationships must correspond to the model [Langmuir et al, 1978]. In terrestrial clastic sediments, where physical mixing unquestionably plays a role, such simple mixing relationships are uncommon and where present are restricted to immobile elements [e.g., McLennan et al, 1993].…”

Eolian dunes and deposits in the western United States as analogs to wind-related features on Mars

“…The Thermal Emission Spectrometer (TES; W29) on MGS has provided compositional constraints for Martian surface materials over areas as small as 3 by 3 km (Christensen et ai, 1998(Christensen et ai, , 2001. TES spectra have revealed two distinct volcanic compositions abundant on the Martian surface: a typical basaltic composition and a slightly more chemically evolved basaltic andésite composition (Bandfield el al., 2000) that is comparable to several rocks at the Mars Pathfinder landing site (Golombek et al, 1999). The TES basalt component has a high concentration in Syrtis Major (Bandfield el al., 2000;Ruff and Christensen, 2002), a classic lowalbedo feature that includes large barchan dunes (Figure 9.8).…”