NASA spots silent Opportunity rover on Mars

NASA's Mars orbiter has caught a glimpse of its solar-powered Opportunity rover, which has been silent since a dust storm enshrouded the red planet over 100 days ago and cut off the 14-year-old probe's access to sunlight.

The image produced by HiRISE, a high-resolution camera aboard NASA's Mars Reconnaissance Orbiter (MRO), shows a small object on the slopes of the red planet's Perseverance Valley.

The object is Opportunity, which was descending into the Martian valley when a dust storm swept over the region a little more than 100 days ago, NASA said in a statement.

The storm was one of several that stirred up enough dust to enshroud most of the red planet and block sunlight from reaching the surface. The lack of sunlight caused the solar-powered Opportunity to go into hibernation.

The rover's team at NASA's Jet Propulsion Laboratory (JPL) in the US, has not heard from it since.

On September 11, JPL began increasing the frequency of commands it beams to the 14-year-old rover.

The tau -- a measurement of how much sunlight reaches the surface -- over Opportunity was estimated to be a little higher than 10 during some points during the dust storm. The tau has steadily fallen in the last several months.

On September 20, when the image was taken, tau was estimated to be about 1.3 by MRO's Mars Color Imager camera.