Breaks detected in NASA's Curiosity Mars rover

NASA's Curiosity Mars rover has developed small breaks in its aluminium wheels, say scientists who have detected the latest signs of wear and tear as the robotic probe continues its journey across the red planet.

The mission's first and second breaks in raised treads, called grousers, appeared in a March 19 image check of the wheels, documenting that these breaks occurred after the last check on January 27.

"All six wheels have more than enough working lifespan remaining to get the vehicle to all destinations planned for the mission," said Curiosity Project Manager Jim Erickson at NASA's Jet Propulsion Laboratory in the US.

"While not unexpected, this damage is the first sign that the left middle wheel is nearing a wheel-wear milestone," said Erickson. The monitoring of wheel damage on Curiosity, plus a programme of wheel-longevity testing on Earth, was initiated after dents and holes in the wheels were seen to be accumulating faster than anticipated in 2013.

Testing showed that at the point when three grousers on a wheel have broken, that wheel has reached about 60 per cent of its useful life.

Curiosity already has driven well over that fraction of the total distance needed for reaching the key regions of scientific interest on Mars' Mount Sharp.

"This is an expected part of the life cycle of the wheels and at this point does not change our current science plans or diminish our chances of studying key transitions in mineralogy higher on Mount Sharp," said Ashwin Vasavada, Curiosity Project Scientist.

Curiosity is currently examining sand dunes partway up a geological unit called the Murray formation. Planned destinations ahead include the hematite-containing "Vera Rubin Ridge," a clay-containing geological unit above it and a sulphate-containing unit above the clay unit.

The rover is climbing to sequentially higher and younger layers of lower Mount Sharp to investigate how the region's ancient climate changed billions of years ago. Clues about environmental conditions are recorded in the rock layers.

During its first year on Mars, the mission succeeded at its main goal by finding that the region once offered environmental conditions favourable for microbial life.

The conditions in long-lived ancient freshwater Martian lake environments included all of the key chemical elements needed for life as we know it, plus a chemical source of energy that is used by many microbes on Earth.

Curiosity has driven 16 kilometres since the mission's August 2012 landing on Mars. Studying the transition to the sulphate unit, the farthest-uphill destination, will require about 6 kilometres or less of additional driving.

Rover drive planners have used enhanced methods of mapping potentially hazardous terrains to reduce the pace of damage from sharp, embedded rocks along the rover's route.

Each of Curiosity's six wheels is about 50 centimetres in diameter and 40 centimetres wide, milled out of solid aluminium.