Modern Scientists like to pretend vast knowledge of outer space and the other planets but since they have not actually been on or inside these planets they have no real idea what is going on.
I thought of it like this.
Back when they did not know of other cultures or countries they would have set out on a ship with no idea what they would find, except a certain arrogance and knowledge of the country and people they came from. They knew of their own culture, minerals, plants, materials and so forth from their own country and would have assumed the same elsewhere until it was proven to them that there actually was a difference.
Scientists on Earth always state that on other planets that they have never been to have certain gases and reasons for the planet being as it is, but they have no idea because they have not been there and have not taken samples, so they simply do not know.