Cleanest manufactured objects

The cleanest objects ever manufactured are the sample return tubes used by NASA's Perseverance Mars rover (which launched on 30 July 2020). Before being loaded into the rover's sample collection mechanism, these test tubes were put through a series of cleaning processes that reduced the quantity of organic compounds within the tubes to less than one part per billion, or no more than 150 nanograms of material in each tube. For the organic compounds the team are specifically looking for on Mars, the tolerance is even lower -- no more than 15 nanograms. For context, a single human thumbprint leaves 45,000 nanograms of organic material on a surface.

To achieve this level of cleanliness, each tube was baked in a kiln at 150C (302F) for 24 hours, then rinsed with a succession of solvents including deionized water, acetone, and isopropyl alcohol. The 43 tubes loaded onto Perseverance were selected from 93 that were manufactured. Five will serve as "witness tubes" – left open to absorb particulates in the Martian atmosphere – while the remaining 38 will be loaded with samples of Martian rock and soil.