Noted Marineris expert has argued for recent volcanism in Marineris.
More on RECENT(?) Dark Volcanic Patches in the Valles Marineris, Mars
Lucchitta, B. K.
LUNAR AND PLANETARY SCIENCE XVII, PP. 496-497.
http://adsabs.harvard.edu/cgi-bin/bib_query?1986LPI....17..496L
Bob Clark
