If there is a possibility that an impurity is present on an object without any visible or odorant indication, does it still hold the status of being Najis?
Just possibility does not establish a concrete evidence of impurity. Everything is Taahir for you unless and until you know that it is Najis. You need to know for sure that it is Najis. Visibility or odor of the Najis item is not necessary which means some Najis items fall on an object in a tiny amount which does not leave a visible trace or odor, but the object has become Najis. Visibility or odor of Najis item can be an evidence in some cases.
'Wassalam.