Parana Valles (220S and 120W) is located at the union of a number of valley systems in ancient cratered land.
The particular characteristic of this site is its existence as a closed depression with many inflow valleys and only one outflow valley. The images of this site, which were provided in great part by the Viking missions, show no evidence of volcanic deposits filling up this depression. This evidence leads to the belief that the sediments of the depression are fluvial sediments. Many of the large craters surrounding this area show higher degrees of erosion than the valleys. This means that the meteorite impacts causing the craters occurred before the formation of valleys in the area.
The valleys surrounding the depression and the most ancient craters are the result of hydrolytic activity during the time period between the ancient meteorite impacts and more recent ones. The recent impacts, which overlap onto the valleys and the other craters, are those which are relatively small in size and whose rims have not had a degree of erosion similar to that of the valleys or the ancient craters. This site results interesting for exploration, because of its location near major valleys and the mouths of ancient streams. Such a location provides the rover type vehicle with an optimum degree of different of different soil samples in a minimum area. The expected types of samples from this site are carbonate rocks, porous rocks, and cements. Porous rocks and cement type rocks are very important to the exobiological study of the region, because of their ability to conserve both fossils and traces of organic materials. By being at the mouth of several ancient streams and a basin, Parana Valles provides explorers with the opportunity of collecting soil samples from different time periods by digging to different depths in water bed. This also allows for the thorough sampling of the region without having to have the rover at very great distances from the landing unit.