Maybe Elon is hoping to someday recover his Roadster after he gets his Mars colony up and running? Whoever does find it out there will see that the car will be in bad shape. The mostly aluminum Falcon rocket stage the Roadster is attached to will probably be fine. In the vacuum of space, all metal parts such as the car's body will not corrode, but other components like plastic, vinyl, nylon and foam rubber seats, interior fixtures and rubber tires will degrade and disintegrate from solar ultraviolet radiation and extreme temperature variations in space, 250 degrees F in sunlight to -250 in shadow. The cherry-red paint job will darken to a blackish-brown color and over time the car will be pitted with small micrometeoroid impacts. Doubtful it will collide with an asteroid or larger object for thousands or perhaps millions of years--space is really big, even in our own solar system. The Starman mannequin dressed in a space suit won't be too bad, neither will the copy of
The Hitchhiker's Guide to the Galaxy inside the glove box, just depends how long it's out there. Actually, there is an entire museum of manmade objects in orbit around the Sun after 60 years of spaceflight--dead and still-functioning space probes, rocket boosters and other debris, same as in Earth orbit, to which the Tesla Roadster is now part of.