Yes, and you can get a separate first discovered for each (if they are not already tagged when you sell).
FYI if you sell your exobio data by system you earn 22 ARX. But if you sell each scanned plant/planet individually you get 22ARX each - so always sell each sample separately
Hello foxwalker,
yes, that's possible - here an example where I had complete samples for Fonticula Campestris - Amethyst on three different planets of that system:
Exobiology is much like exploration data. Each system, and planetary body within that system is considered a unique instance. In both cases, the bonus is for first discovery for each instance.