Opportunity is over and out after 15-year exploration of Mars

Opportunity, the intrepid NASA rover that spent 15 years on Mars climbing in and out of craters to gather evidence of the planet's watery past, has been brought down by tiny particles of dust.

It's a humble ending for a machine that survived a 300 million-mile journey through space, executed a hole-in-one landing, and set a record by driving more than 28 extraterrestrial miles.

Opportunity's last transmission to Earth occurred on June 10 amid an epic Martian dust storm. Still, NASA engineers remained hopeful that when the dust settled, the rover would recharge its solar-powered batteries and resume its superlative mission.

Until Wednesday.

After sending more than 1,000 unanswered commands to the Smart-car-sized vehicle, NASA officials announced that Opportunity's mission had officially come to an end.

"With a sense of deep appreciation and gratitude, I declare the Opportunity mission is complete," Thomas Zurbuchen, associate administrator of NASA's Science Mission