Assessment of Mars Pathfinder landing site predictions

Remote sensing data at scales of kilometers and an Earth analog were used t o accurately predict the characteristics of the Mars Pathfinder landing sit e at a scale of meters. The surface surrounding the Mars Pathfinder lander in Ares Vallis appears consistent with orbital interpretations, namely, tha t it would be a rocky plain composed of materials deposited by catastrophic floods. The surface and observed maximum clast size appears similar to pre dictions based on an analogous surface of the Ephrata Fan in the Channeled Scabland of Washington state. The elevation of the site measured by relativ ely small footprint delay-Doppler radar is within 100 m of that determined by two-way ranging and Doppler tracking of the spacecraft. The nearly equal elevations of the Mars Pathfinder and Viking Lander 1 sites allowed a pred iction of the atmospheric conditions with altitude (pressure, temperature, and winds) that were well within the entry, descent; and landing design mar gins. High-resolution (similar to 38 m/pixel) Viking Orbiter 1 images showe d a sparsely cratered surface with small knobs with relatively low slopes, consistent with observations of these features from the lander. Measured ro ck abundance is within 10% of that expected from Viking orbiter thermal obs ervations and models. The fractional area covered by large, potentially haz ardous rocks observed is similar to that estimated from model rock distribu tions based on data from the Viking landing sites, Earth analog sites, and total rock abundance. The bulk and fine-component thermal inertias measured from orbit are similar to those calculated from the observed rock size-fre quency distribution. A simple radar echo model based on the reflectivity of the soil (estimated from its bulk density), and the measured fraction of a rea covered by rocks was used to approximate the quasi-specular and diffuse components of the Earth-based radar echos. Color and albedo orbiter data w ere used to predict the relatively dust free or unweathered surface around the Pathfinder lander compared to the Viking landing sites. Comparisons wit h the experiences of selecting the Viking landing sites demonstrate the eno rmous benefit the Viking data and its analyses and models had on the succes sful predictions of the Pathfinder site. The Pathfinder experience demonstr ates that, in certain locations, geologic processes observed in orbiter dat a can he used to infer surface characteristics where those processes domina te over other processes affecting the Martian surface layer.