speculated upon/guessed/conjestured

Although stories about aliens have never been officially confirmed, their existence has been widely speculated upon.

 

Hi,

Does the bolded part refer to "people have widely guessed/conjestured their existence?" Thanks.

 

Angliholic

Does the bolded part refer to "people have widely guessed/conjestured their existence?

I was about to say "yes" to your question but now I'm not so sure "guessed" really applies in this context. It's close but it just doesn't seem quite right. Conjectured certainly does apply though. By the way, please note the spelling of "conjectured".