In a blog post, NASA said the golf cart-sized Opportunity had a "very active" winter since the bot, which uses solar energy, was able to receive cleaner solar rays -- even during the dark Martian winter. Martian years are 1.9 times longer than Earth years, making this Opportunity's seventh winter on Mars.
Opportunity has spent the past few years exploring a 14-mile-wide crater named Endeavour, where it has used its rock abrasion tool to remove surface crust from a rock NASA named "Private John Potts" after a member of the Lewis and Clark Expedition's Corps of Discovery.
Using its robotic arm, Opportunity has been able to examine the composition and texture of the rock's interior. NASA credited Opportunity's surprising longevity -- 48 times longer than planned -- to choosing north-facing slopes in the winter that allow Opportunity's solar panels to collect energy.
With the winter solstice over on Mars, NASA predicts Opportunity will have plenty of sunlight to keep it going through the year.