40th Lunar and Planetary Science Conference (2009) 1374.pdf EVIDENCE OF LATE-STAGE FLUVIAL OUTFLOW IN ECHUS CHASMA, MARS. M. G. Chapman1, G. Neukum2, A. Dumke2, G.Michaels2, S. van Gasselt2, T. Kneissl2, W. Zuschneid2, E. Hauber3, and N. Mangold4, 1U.S. Geological Survey, 2255 N. Gemini Dr., Flagstaff, Arizona, 86001 (
[email protected]); 2Institute of Geo- sciences, Freie Universitaet Berlin, Germany; 3German Aerospace Center (DLR), Berlin, Germany; and 4LPGN, CNRS, Université Nantes, France. Introduction: New high-resolution datasets have We interpret this late-stage outflow to have been prompted a mapping-based study of the Echus Chasma formed by water based on several lines of evidence, and Kasei Valles system. Some of the highlights of the first being the “washed” appearance of the At5 lava our new findings from the Amazonian (<1.8 Ga) pe- lobe. Where the mouth of the lava-lobe-confined riod in this area include (1) a new widespread platy- south shallow channel debouches into Echus Chasma, flow surface material (unit Apf) that is interpreted to be the floor of the chasma is marked by a very straight, 2,100-km-runout flood lavas sourced from Echus likely fault controlled/confined, north boundary of Chasma; and (2) a fracture in Echus Chasma, identi- dark albedo material (white arrows on Fig. 2). This fied to have sourced at least one late-stage flood, that boundary correlates with the bottom edge of an up- may have been the origin for the platy-flow material lifted plate (insert Fig. 1). The albedo boundary is and young north-trending Kasei floods.