Mona Lisa replicas and reinterpretations
After restoration, the Prado's "Mona Lisa" revealed details covered by previous restorations and layers of varnish.
Furnishings and fabrics were enhanced, as well as landscape and facial features.
It is anticipated that such revelations may offer further insight into Leonardo's original.
Experts at the Louvre reportedly supported the Prado museum's findings.
The Prado replica was subsequently transported to the Louvre in 2012 to be displayed next to "Mona Lisa" as part of a temporary exhibition.
Two nude paintings bearing similarities to Leonardo da Vinci's original were part of a 2009 exhibition of artwork inspired by "Mona Lisa".
Displayed at the Museo Ideale in Leonardo's hometown of Vinci, near Florence, some believe one of the paintings – dating from Leonardo's time – to be the work of Leonardo himself, and it has at times been credited to him.
Other experts theorize the painting, one of at least six known to exist, may be just another copy painted by "followers" of Leonardo.
Scholarly dispute persists as to artist, subject and origin.
The nude in question, discovered behind a wall in a private library, reportedly belonged to an uncle of Napoleon Bonaparte, who owned another of Leonardo's paintings.
Facial features bear only vague resemblance, but landscape, compositional and technical details correspond to those of the "Mona Lisa" known worldwide today.
Roberto Vittori
The astronaut also had a painting of the artist George Pusenkoff titled "Single Mona Lisa (1:1)" with him and took photos with it on the International Space Station. It is the ultimate continuation of the project "Mona Lisa Travels" developed by Pusenkoff and could only be realized under difficult conditions. The authorities found the idea good in theory, but constantly put forward new reasons why the project was unrealizable. Only when George Pusenkoff wrote to the then Italian ambassador in Russia, Gianfranco Facco Bonetti, the possibility of realizing the idea arose. The connection between science and art, which was also important in Leonardo da Vinci's life, found here an "actualization" in the form of this journey of an image of Mona Lisa into space. For the action, Pusenkoff's painting was removed from the frame so that it could be rolled. On April 25, 2005, Vittori took the painting back to the Earth with him.