If the Curiosity rover had been sent to Mars in ancient times, it might have found itself sinking in a stream.
The 2,000-pound super-rover, which made its now-legendary landing on Mars on August 6, has come across stones in conglomerate rock suggesting that water must have flowed there in the past.
One such rock outcrop is called Hottah, after Hottah Lake in Canada's Northwest Territories. It looks like someone took a jackhammer and lifted up a sidewalk, said John Grotzinger, lead scientist for the Curiosity mission, at a press conference Thursday.
The consensus is that "this is a rock that was formed in the presence of water," Grotzinger said. "We can characterize that water as being a vigorous flow."
In and around this bedrock, Curiosity has come across rounded gravels. The rocks appear to have been subjected to a sediment transport process, carried by either water or wind, said scientist Rebecca Williams of the Planetary Science Institute in Tucson, Arizona.
The gravels seem too large to have been transported by wind, meaning it's likely that this is a stream bed.
A second rock outcrop, called Link, holds similar evidence. Scientists used data from Curiosity and the orbiters at Mars to enhance their understanding of the area.
The water flowing in these rock formations was probably somewhere between ankle and hip deep, said Curiosity science co-investigator William Dietrich of the University of California, Berkeley.