"Opportunity used science instruments on its robotic arm to examine the hole it dug with its right front wheel on Sol 23," said the National Aeronautics and Space Administration team at the Jet Propulsion Laboratory in Pasadena, California.

"The trench is about 50 centimeters (20 inches) long by 20 centimetersinches) wide by 10 centimeters (4 inches) deep," it said, adding, "Sol 24's wake-up music was 'Trench Town Rock' by Bob Marley."

Opportunity, said the lab, "will also peek at its right front wheel with the panoramic camera to see what materials got stuck on the wheel from the trenching activity."

Opportunity landed on Mars January 24. It's identical twin Spirit landed on the opposite side of Mars on January 3.

Both rovers have six wheels and weigh some 180 kilos (384 pounds). They are equipped with four instruments designed to carry out geological studies as well as a powerful drills.

Their mission is to study the geology of Mars for three months, and try to determine if the conditions necessary to life once existed there.

Spirit, out of commission for about a week last month with computer problems, Wednesday progressed 22.7 meters (yards) and stopped at a depression called the Laguna Hollow in the Bonneville Crater.

There, said NASA, the robot "wiggled its wheels to disturb or scuff the fine, dust-like soil at this location, which allows for more detailed observations with the instruments on the robotic arm."

SPACE.WIRE