NASA's Perseverance rover, which lands on Mars on Feb. 18, 2021, will carry 11 metal parts made with 3D printing. Five of the parts are in the PIXL instrument, and the six other 3D-printed parts can be found in an instrument called the Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE).
The PIXL instrument, which is short for the planetary instrument for X-ray lithochemistry, will help the rover seek out signs of fossilized microbial life by shooting X-ray beams at rock surfaces to analyze them. MOXIE will test technology that, in the future, could produce industrial quantities of oxygen to create rocket propellant on Mars, helping astronauts launch back to Earth.
As secondary structures, Perseverance's printed parts wouldn't jeopardize the mission if they didn't work as planned.
Here's the news from NASA.