HOAX! Spain - Cathedral 1102

Here is a
Mystery!
See if you can
suggest an answer

In the Spanish City of
SALAMANCA

the Cathedral there
was built in 1102

I have asked my work
colleagues if this
item is TRUE...

and they assure me
that it is INDEED
(and nobody has an answer)

There is a small detail
carved into the
masonery which
amazes everyone
that sees it...
 

Can You Suggest how a

20th Century Astronaut

came to be carved by a

12th Century Stonemason?