[pluto (Hugh)]

Elon Musk is not sending his car to Mars.
The media has really done a terrible job at understanding and reporting on this.
If all goes well the Tesla will be placed into a Heliocentric Mars transfer orbit - so it will be in orbit around the Sun with its periapsis at a distance from the Sun equal to the Earth and an apoapsis at a distance equal to Mars' orbit. When the Tesla gets to the distance of Mars' orbit, Mars won't be there!
TLDR: At no point will the Tesla be anywhere near Mars.

It does sound silly but it makes sense. For example it will demonstrate the ability of the rocket to deliver at least a couple of tons into a Heliocentric orbit, plus it will give SpaceX real world experience with the type of flying nessesary to get stuff to Mars. Plus it's obviously some good advertising for Tesla.