NASA's Opportunity Mars Rover remains silent

NASA scientists are yet to hear from the Mars Opportunity Rover, which has been silent since a global dust storm enshrouded the red planet.

According to the US space agency, it is possible that a layer of dust deposited on the rover's solar panels by the dust storm is blocking sunlight that could recharge its batteries.

No one can tell just how much dust has been deposited on its panels, NASA said in a statement.

The agency's Jet Propulsion Laboratory is employing a combination of listening and commanding methods in case Opportunity is still operational.

A windy period on Mars -- known to Opportunity's team as "dust-clearing season" -- occurs in the November-to-January time frame and has helped clean the rover's panels in the past.

The team remains hopeful that some dust clearing may result in hearing from the rover in this period.

Opportunity has exceeded its expected lifespan many times over. Both Opportunity and its twin, Spirit, were designed to last only 90 days on the Martian surface, with the expectation that the planet's extreme winters and dust storms could cut their mission short.

The rover has lasted nearly 15 years. It last communicated on June 10 before being forced into hibernation by the growing dust storm.