Nasa calls time on silent Opportunity Mars rover
The 15-year mission of "Oppy" the robot is declared over after repeated failed attempts to contact it.
The US space agency (Nasa) has called time on its Opportunity Mars rover.
The six-wheeled robot last contacted Earth in June last year, just before it was enveloped in the darkness of a global dust storm.
Engineers hoped Oppy would power back up when the skies cleared and sunlight hit its solar panels again - but there has not been a peep out of the rover.
The routine prompt commands that have been sent to Opportunity will now end.
The decision brings the curtain down on one of Nasa's most successful ever ventures.
Oppy and its twin robot, called Spirit, landed on Mars in January 2004 with the goal of investigating whether the planet ever had the conditions necessary to support life.
The mission team believed its "mobile geologists" would work for at least 90 Martian days and be able to travel 1km or more.
In the end, the golf-buggy-sized rovers surpassed all expectations.
Spirit worked for six years, logging a drive distance of almost 8km; and Opportunity trundled on for 45km over 15 years - a record for any wheeled vehicle off Earth.
The science the rovers returned was no less remarkable. They proved the planet in ancient times was very different to the freezing, desiccated world we see today.
It was warmer and wetter. Indeed, there was evidence in the rocks examined by the rovers' instruments that bodies of water would sit at, or just under, the surface for prolonged periods.
Oppy made this discovery almost as soon as it had landed in a small depression known as Eagle Crater.
Its cameras spied small spherules that were quickly dubbed "Blueberries" because of their shape and small size. These concretions contained a lot of hematite, an iron-rich mineral that forms (often) in the presence of water.
Scientists concluded this water would have been fairly acidic and therefore not that friendly to life, but then later in the mission it came across clay minerals and gypsum deposits - clear signs of water interactions under much more neutral, and hospitable, conditions.
Opportunity's silence leaves just the one working rover on Mars.
The Curiosity robot landed in 2012 in Gale Crater. It has a plutonium battery and so was able to ride out the darkness of the recent dust storm with ease.
Nasa is currently preparing a near-twin of Curiosity, which will be delivered to the planet in February 2021. It will be joined on the surface a month later by Europe's Rosalind Franklin rover, although at a very different location.
The US space agency currently also operates a static lander, called InSight, which touched down in November last year.
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