sentence: Some valleys appear to have rivers.
sentences_before: Scientists still believed that liquid ethane and methane would be found near Titan's poles, where they expected to find lots of liquid. At Titan's south pole, an large dark area named Ontario Lacus was the first lake identified, possibly created by rain as clouds are often seen in the area. A possible shoreline was also identified at the pole in radar images.
concept_name: valley
headings: Lakes of Titan
categories: Saturn's moons