Washington, Jan 30 (IANS): In its latest selfie sent back home, NASA's Curiosity rover shows the car-size mobile laboratory beside a dark dune where it has been scooping and sieving samples of sand.

The new selfie combines 57 images taken by the Mars Hand Lens Imager (MAHLI) camera at the end of Curiosity's arm.

The rover has been investigating a group of active sand dunes for two months, studying how the wind moves and sorts sand particles on Mars.

The site is part of Bagnold Dune Field, which lines the northwestern flank of Mars' Mount Sharp.

When the component images were taken, the rover had scuffed the edge of "Namib Dune" and collected the first of three scoops of sand from that dune.

During processing, an actuator in the sample-processing device did not perform as expected when commanded. This week, the Curiosity team is identifying possible reasons for the actuator's performance.

“The rover responded properly to this unexpected event. It stopped moving the actuator and halted further use of the arm and sampling system,” said Steve Lee, deputy project manager for Curiosity at NASA's Jet Propulsion Laboratory, Pasadena, California.

One part of the dune investigation is to view the same location repeatedly to check for movement of sand grains caused by wind on Mars.

If movement occurs, the team can use the rover's wind measurements to figure out the strength and direction of the winds that caused the movement.

Researchers are evaluating possible sites for the next use of Curiosity's drill to collect rock-powder samples of the bedrock in the area.

Curiosity reached the base of Mount Sharp in 2014 after fruitfully investigating outcrops closer to its landing site and then trekking to the layered mountain.