NASA rover Curiosity has discovered gravel once carried by the waters of an ancient stream that 'ran vigorously' through the area, says the US space agency.
Evidence of water has been found before but this is the first time gravel from a stream bed has been discovered.
The rocky Hottah outcrop looks 'like someone jack-hammered up a slab of city sidewalk, but it's really a tilted block of an ancient stream bed,' project scientist John Grotzinger said in a statement. Curiosity, which has been exploring Mars since early August, also investigated a second outcrop known as Link.
Curiosity is on a two-year mission to investigate whether it is possible to live on Mars and to learn whether conditions there might have been able to support life in the past.