More signs of past water on Mars have been uncovered by space agency Nasa's Curiosity rover.
Powder drilled from a Martian rock last week revealed evidence of drinkable water and conditions favourable to life. Now instruments on the rover have found more water-bearing minerals in the area around the rock.
Curiosity is exploring a region within Gale Crater, near the Martian equator, called Yellowknife Bay. Scientists believe that billions of years ago water poured down the rim of the crater and formed streams that may have been up to three feet deep.
The new discoveries were made using the infrared imaging capability of Curiosity's mast camera, and an instrument that shoots neutron particles into the ground to probe for hydrogen.
Differences in brightness between near-infrared wavelengths of light can indicate the presence of some hydrated minerals that have been altered by water.
"With Mastcam, we see elevated hydration signals in the narrow veins that cut many of the rocks in this area," said Dr Melissa Rice, from the California Institute of Technology in Pasadena.
"These bright veins contain hydrated minerals that are different from the clay minerals in the surrounding rock matrix."
The Russian-made Dynamic Albedo of Neutrons (DAN) instrument detected hydrogen in water molecules bound into minerals in the soil beneath the rover. Yellowknife Bay contained more water than other areas previously visited by Curiosity, the results showed.
"More water is detected at Yellowknife Bay than earlier on the route," said DAN deputy principal investigator Dr Maxim Litvak, from the Space Research Institute in Moscow. "Even within Yellowknife Bay, we see significant variation."
The findings were presented at the Lunar and Planetary Science Conference in The Woodlands, Texas.