[alganet]

The 10.000 was a misquote from the original paper they referenced:

https://www.nature.com/articles/s41550-021-01550-6

Here you can read that, in fact, a class 1.000 cleanroom was used.

This is also consistent with the description of the facility:

https://en.wikipedia.org/wiki/Extraterrestrial_Sample_Curati...

According to the paper, five different chambers were used. You can read the entire procedure down to materials of cleaning spatulas.