While it is admittedly a little silly for Elon Musk to be and eventually, hopefully, into a Mars orbit, it isn't the first car to go into space. It isn't even the second or the third. It's the fourth, and it was preceded by the three Apollo-era electric Lunar Rovers, built by Boeing with a little help from General Motors.
The Lunar Roving Vehicle, aka Lunar Rover, aka Moon Buggy, was a highly specialized electric vehicle designed to traverse the lunar surface with two astronauts, their gear and scientific samples aboard. The suspension, wheels and motors were developed by General Motors Defense Research facility in Santa Barbara, California and the rest was designed by Boeing in Seattle. Assembly took place in Huntsville, Alabama by Boeing.
The Moon Buggy weighed just 460 pounds on Earth and was designed to carry a total payload of more than 1,000 pounds. Almost the entire structure including chassis, suspension and seating was made from aluminum to save weight. The buggy had a ground clearance of 14 inches when fully loaded. Four 0.25-horsepower DC electric motors motivated it, one at each wheel, and electricity came from two 36-volt nonrechargeable silver-zinc potassium hydroxide batteries.
The Tesla Roadster, by comparison, features lithium-ion batteries that produce 375 volts and electric motors that provide 288 horsepower. Unfortunately, the Roadster won't be able to use any of that power as it careens silently towards Mars, a message of "Don't Panic" emblazoned on its dash. It will be traveling at a speed of 7 kilometers per second though, which is a little better than it was capable of doing on Earth.
While the Roadster isn't the first EV in space, Musk has said there is a tiny chance that it could crash into the surface of Mars, which would make it the first car to land on another planet. Fingers crossed.