“…It is more likely that subsurface aquifer drainage was episodic over the esti-the valley. There are no other traces of subsequent erosion: thus, we assume that the discharge of this intravalley lake mated two Gyr activity of Ma'adim Vallis Grin and Cabrol, 1997;Cabrol et al, 1997). was the last active episode of Ma'adim Vallis.…”