The first rock nuzzled by Nasa's Mars Curiosity rover is turning out to be a bit more unusual than scientists thought it would be.
Curiosity used its robot arm to touch a football-sized pyramid-shaped rock for the first time two weeks ago. It also shot the rock dozens of times with a laser.
The results surprised scientists. They said it is not like other rocks seen on Mars - it has more sodium and potassium.
Scientist Edward Stolper said the rock is more like rare volcanic rocks seen on Earth in places such as Hawaii. Those rocks are formed under high pressure, deep underground and once contained water.
Scientists do not know how old the Martian rock is.