A plutonium-238 pellet assembled in a high-strength graphite impact shell for Multi-Mission Radioisotope Thermoelectric Generator.
The file is copied from Wikimedia Commons {accessed 2021-01-01}: https://commons.wikimedia.org/wiki/File:Fueling_of_the_MSL_MMRTG_002.jpg
See also: https://rps.nasa.gov/power-and-thermal-systems/power-systems/ {accessed 2021-01-01}
mars_radioisotope_thermoelectric_generator.jpg
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Idaho National Laboratory, CC-BY-2.0