(Released 15 July 2002)
Hrad Valles is located north-northwest of the large Elysium Mons volcanic complex and is yet another example of a channel that likely carried fluids. The formation of Hrad Valles may have differed from some other channels on Mars in that its proximity to Elysium Mons could have promoted significant interactions between ground water or ice and the lavas of the volcano. Some scientists have suggested that very hot subsurface lavas may have intruded the local rocks and quickly melted and vaporized ground ice, causing the overlying rock to be broken up and possibly ejected. The breakup and ejection of the local rocks, combined with the newly formed volcanic rocks and melted ice, could have resulted in the formation of mudflows at the source of Hrad Valles, and over the longer term, continued release of melt water that carved the long, sinuous channel.