NASA's Opportunity rover has officially concluded its 15-year mission on Mars, the agency announced today (Feb. 13). Eight months after a raging dust storm incapacitated Opportunity's solar panels, leaving it unable to communicate with Earth, NASA has stopped waiting for it to wake up and will no longer listen for signals from the rover.
Opportunity, NASA's longest-running Mars rover, outlived its twin rover, Spirit, which went silent in 2010 after getting stuck in a sand trap and running out of power. Both rovers launched to the Red Planet in 2003 and are collectively known as NASA's Mars Exploration Rovers.
The twin rovers made some remarkable scientific discoveries over the course of their missions on the Red Planet. Here we'll focus on some of the stranger things Opportunity and Spirit have spotted on Mars.
Blueberries on Mars
Just a few months after the Opportunity rover arrived at the Red Planet, its cameras spotted this deceptively delicious-looking patch of rocks near the landing site. Not knowing exactly what they were looking at, scientists starting calling these strangely spherical rocks "blueberries."
It's unclear exactly how these rocks came to be, but scientists believe that they constitute one of the earliest pieces of evidence that Mars had a very watery past.
If those Martian blueberries got your mouth watering, get a load of this. A mysterious object that bears a striking resemblance to a powdered, jelly-filled doughnut mysteriously appeared in front of the Opportunity rover's panoramic camera on Jan. 8, 2014. Earlier images of that exact spot were suspiciously doughnut-free.
No one knew what it was or where it came from, but people on Earth were captivated by the Martian doughnut — in other words, they were eating it up! After weeks of analyzing the images from Opportunity, NASA scientists determined that what looked like a jelly-filled pastry was actually just a plain old rock that had been kicked up and displaced by the rover's wheels.
Full Story: NASA's 'Jelly Doughnut' Mars Rock Mystery Solved
The first extraterrestrial meteorite
On Jan. 6, 2005, the Opportunity rover found a basketball-size meteorite on Mars — the first meteorite ever discovered on another planet.
Opportunity's spectrometers scoped out the space rock and determined that it's mostly made of iron and nickel. NASA named the meteorite Heat Shield Rock because it was spotted near Opportunity's heat shield, which was discarded during the rover's landing in 2003.
A Martian bunny rabbit
NASA's Opportunity rover never found life on Mars, but in a photo of Meridiani Planum, it did find a mysterious object that looks like a long-eared bunny rabbit. The image was released in March 2004 (about two months after Opportunity arrived at the Red Planet) as part of the rover's "mission success" panorama.
The bunny's ears appeared to move slightly in the weak Martian wind, so it couldn't have been a rock. NASA engineers said it appears to be "a piece of soft material that definitely came from our vehicle," like cotton insulation or a Vectran cover.
A person on Mars?
Opportunity's twin, a nearly identical rover named Spirit, also made some strange discoveries during its time roving around the Red Planet. In 2007, Spirit snapped a photo of what vaguely resembles a human-like figure perched on a rock.
While some interpreted the image to be evidence of life on Mars, NASA assured everyone that it was just a rock.
Full Story: Female Figure on Mars Just a Rock
"Phallic" rover tracks
Last but certainly not least on our list of the strangest things seen by NASA's Mars Exploration Rover mission is a set of tire tracks left behind by the Spirit rover.
Shortly after Spirit touched down on the Red Planet in 2004, it was executing a turn that left what seemed to be a phallic shape etched into the Martian surface. A Reddit user discovered the photo nearly a decade later, and it quickly became the subject of a viral meme.
Full Story: Penises on Mars? Grow Up, Internet
Need more Mars rover discoveries? We've got you covered: