WHITE ROCK - AN ERODED MARTIAN LACUSTRINE DEPOSIT()

The existence and location of ancient lake sites and sediments have im portant implications for Martian paleoclimate and exobiology. White Ro ck, an enigmatic crater interior deposit, may be the eroded remnant of such a lacustrine deposit. Stereogrammetric analysis of newly process ed Viking images allows better determination of the dimensions of Whit e Rock (12.5 x 15 km, thickness 180 to 540 m, volume similar to 40 km( 3)), reveals differences in erosion patterns that may reflect differen ces in depositional environment, and allows the identification in or o n the crater wall of a possible source region of the high-albedo White Rock material. If White Rock is the remnant of a once-larger deposit, then open-system circulation may have been required to deliver the re quired quantity of evaporites.