NASA's Mars Exploration Rover Opportunity is shown in this handout photo released to Reuters July 29, 2014.
NASA's Mars Rover Curiosity may have to find a new route to its destination Mount Sharp after getting stuck in sand in the "Hidden Valley".
The one-tonne Curiosity is on a mission to Mount Sharp, a 5.5 km high mountain in the centre of Mars' Gale Crater, and had to turn back after finding the sand surprisingly slippery, reports space.com.
"We need to gain a better understanding of the interaction between the wheels and Martian sand ripples, and 'Hidden Valley' is not a good location for experimenting," Jim Erickson, Curiosity project manager, was quoted as saying.
The goal of the six-wheeled Curiosity is to climb up Mount Sharp foothills and read the history of change from a warm and wet planet in the past to the cold, dry Mars of today.
Curiosity has covered about 8 km of the way to Mount Sharp and has about 3.2 km to go, which the team hopes to get to by the end of 2014.