ROCKS AND AEOLIAN FEATURES IN THE MARS PATHFINDER LANDING SITE REGION- VIKING INFRARED THERMAL MAPPER OBSERVATIONS

Albedo, rock abundance, and thermal inertia derived from Viking infrar ed thermal mapper observations provide information about the surface m aterials within the Mars Pathfinder landing ellipse in Ares Vallis. Re lative to the rest of Mars, the site has an intermediate albedo (0.19- 0.23), intermediate-to-high bulk thermal inertia (410-540 J m(-2) s(-0 .5) K-1), and high rock abundance (18-25%). At local scales the actual surface distribution of rocks might be heterogeneous, as on terrestri al catastrophic flood surfaces, where rocks tend to be concentrated on fluvially armored surfaces and/or bars. Albedo increases and thermal inertia decreases from the northeast to the southwest in the ellipse, owing to (interpreted) windblown dark sand from Acidalia Planitia. If Mars Pathfinder lands at the southwest end of the landing ellipse, the scene is likely to be the most similar to that of the Viking 1 lander ; while a landing at the northeast end of the ellipse is most likely t o provide a view that is different from the Viking sites because of lo w-albedo material. A landing at the center of the ellipse might put th e spacecraft near one of two crater clusters that are interpreted to h ave dark sandy material in or on their ejecta. Aeolian activity during the 30-day Primary Mission might be limited because it is mid-norther n summer, a time in which no historic dust storms have been seen in th e region, and a season when regional winds should be weak relative to other times during the year.