Where do they come up with this 'stuff'?

Watched a few episodes, some are very interesting, but when they strip comets and/or planets apart, how are they doing this, do they have some data collected or is this pure speculation?
I don't mind these postulations, but present it as such, do not present it like this is reality when likely only a fraction of the content of this series has any basis in science.
Tell us how you come to your conclusions if based upon data, and clearly state when you switch over to speculation informing us that we are viewing an opinion on the matter.
It may not be obvious to those without a science background that much of this speculation and I think that is a big mistake adding this unconfirmed mix into the otherwise great series, trying to teach the masses science is more than welcome, add the footnote when needed as other series had please...