The NASA Mars rover Opportunity is ailing but still functional after eight years on the red planet's surface. That's a very long time in rover years.
Most of Opportunity's missions have involved looking for water on Mars. In addition, it's been transmitting a signal that helps scientists gauge the rotation of the red planet—thereby helping determine whether Mars' core is liquid or solid.
"The top priority at [Opportunity site] Greeley Haven is the radio-science campaign to provide information about Mars' interior," said JPL's Diana Blaney, deputy project scientist for the mission. This study uses weeks of tracking radio signals from the stationary rover to measure wobble in the planet's rotation. The amount of wobble is an indicator of whether the core of the planet is molten, similar to the way spinning an egg can be used to determine whether it is raw or hard-boiled.
Opportunity's data collection also led to what one NASA scientist called 'slam-dunk' evidence that liquid water once flowed on Mars. It accomplished this by detecting veins of the gypsum, a 'hydrated' mineral that had to have been formed with the help of water.
A large chunk of Opportunity's lifespan was spent on that mission. The journey alone took three years, and in the mission's last year Opportunity travelled almost five miles. This may not seem like much, but the solar-powered rover is built for safety and precision rather than speed.
How much longer will Opportunity last? No one knows.
Opportunity's counterpart on the other side of Mars, called Spirit, was declared dead from hypothermia last year after a malfunction kept its solar panels from following the sun.
Now, Opportunity's robotic arm is malfunctioning, but the team of scientists have sworn to get everything they can out of the venerable rover. John Callas, Opportunity's project manager, told SPACE.com, "We just keep charging ahead as if every day is our last day, and we want to maximize the science we can do with this vehicle."