The second geocaching trackable in space is TB5EFXK which is attached to the SHERLOCK calibration target onboard the Mars Perseverance Rover, which landed on Mars on 18 February 2021. Geocachers will be given the opportunity to virtually discover the trackable once the WATSON camera sends back its first photographs of the calibration target that contains the tracking code number. The code is printed on a prototype helmet visor material that will be used to test how well it can withstand the Martian environment. This will help scientists in creating a viable Martian spacesuit for future manned missions to Mars.