A group at Caltech has been studying images from the Mars Reconnaissance Orbiter of a 100-square-kilometer area with ridge-like features that lies next to a region called Aeolis Dorsa that has been speculated to be a dried-up ocean bottom. They see evidence that the features of the ridges match well  that seen for channels of river deltas going into seas on earth. So this supports the possibility that there was in fact an ocean there long ago.

• Red Planet Riviera: Ancient Mars Ocean Found? – Discovery News
• Evidence for a Martian Ocean – Caltech

Comparison of exhumed delta in sedimentary rocks on Mars (left) with a modern
delta on Earth (right). On the left, a shaded relief map shows elevated, branching,
lobate features in Aeolis Dorsa, Mars, interpreted as resistant channel deposits that
make up an ancient delta.  These layered, cross-cutting features are typical of
channelized sedimentary deposits on Earthand here are indicative of a
coastal delta environment.
Credit: DiBiase et al./Journal of Geophysical Research/2013 and USGS/NASA Landsat

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Perhaps the next NASA rover to go to Mars in 2020 will examine Aeolis Dorsa. Recently NASA released details of the design of the rover, which will be based on the Curiosity design. The scientific instruments will be chosen in a competitive process. The primary goal will be to look for signs of past life. The vehicle will also gather up samples that a future mission with a lander and return vehicle could take back to earth for closer examination.

• 2020 Mission Plans: Science Team Outlines Goals For NASA’s 2020 Mars Rover – NASA JPL
• 2020 rover to look for signs of past life on Mars – Spaceflight Now
• Next NASA Rover Science Goals Are Outlined – Aviation Week