Pics of Mars Taken by a Time Traveler

I only have passing knowledge of ufologists in general, so I can't name many. But this is hands-down the Billy Meier Mars Hoax photos. They're fairly infamous in that every photo was tracked down as a pre-existing image out of books and off shows. There's a pretty good video summary of that debunking floating around YT somewhere. I can't remember the title, so spitball-searching with keywords is making it hard to find it buried within all the Billy Meier returns in searches, though.

This Mental Floss article names a few of the sources, so there's at least that out there at the ready that names photos' specific sources.