• The Curiosity Rover on Mars

    The Curiosity Rover's handlers use its soil sample analysis instrument to "sing" it "Happy Birthday" on its Martian anniversary. (Photo: NASA Goddard/YouTube)

NASA's Curiosity Rover landed on Mars on August 5, 2012 (Pacific Time), which makes today its fourth Martian "birthday." Each year, to celebrate, Curiosity's handlers use the rover's Sample Analysis at Mars (SAM) instrument to "sing" it "Happy Birthday."

SAM's job is to collect and analyze soil samples from the red planet. When SAM ingests a soil sample, it vibrates at various frequencies, producing sound. In the video below, SAM scientist Florence Tam explains how the Curiosity team are able to get the instrument to sound the notes of "Happy Birthday."

Since September 11, 2014, Curiosity has been exploring the terrain around Mount Sharp, a 5,500-meter peak within Mars' Gale Crater that is expected to hold significant clues to the planet's formation and geological history. According to NASA's Jet Propulsion Laboratory, in its four years, Curiosity has returned more than 128,000 images, fired its laser more than 362,000 times and driven 13.5 kilometres. 

The rover's mission was recently extended through October 2018, and its handlers are hoping to use it to explore three distinct geological "units" or rock layers on the lower slopes of Mount Sharp.