Cars just don’t have those kinds of internal pressures.
The real forces that will tear the car apart over hundreds of millions of years in space, Carroll said, are solid objects and — most important — radiation.
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It’s unlikely that the vehicle could avoid the kind of collisions with micrometeoroids that leave space junk riddled with craters over time, Carroll said. But assuming those collisions don’t tear the car apart, the radiation will.
On Earth, a powerful magnetic field and the atmosphere largely protect humans (and Tesla Roadsters) from the harsh radiation of the sun and cosmic rays. But objects in space have no such protections.
“All of the organics will be subjected to degradation by the various kinds of radiation that you will run into there,” Carroll said.
Organics, in this case, doesn’t mean the bits of the car that came from animals, such as its leathers. Instead, it includes all the plastics in the sports car and even its carbon-fiber frame. Those materials “are made up largely of carbon-carbon bonds and carbon-hydrogen bonds,” Carroll said.
The energy of stellar radiation can cause those bonds to snap. And that can cause the car to fall to bits as effectively as if it were attacked with a massive knife.
“When you cut something with a knife, in the end, you’re cutting some chemical bonds,” Carroll said.
A knife cuts those bonds in a straight line. But radiation will split them at random, causing organic materials — leather seats, rubber tires, paints, perhaps even the carbon-fiber body — to discolor, flake and splinter away.
And under the harsh glare of the unshielded sun, Carroll said, that process could happen fast. “Those organics, in that environment, I wouldn’t give them a year,” he said.
Materials with fewer bonds holding them together will disintegrate first, Carroll said. Anything hidden behind an inorganic (no carbon bonds) shield would last longer, though eventually even the plastic woven into the convertible’s glass windshield would discolor and come apart. The sturdy carbon-fiber parts would probably be the last to go, he said.
Eventually, the Roadster would probably be reduced to just its well-secured inorganic parts: the aluminum frame, internal metals and any glass parts that don’t shatter under meteor impacts. (The idea that glass melts over long time spans is a myth, he said.)
Richard Sachleben, a retired chemist and member of the American Chemical Society’s panel of experts, largely agreed with Carroll’s assessment, though he did suggest it would probably still be somewhat recognizable, at least after a million years.
“A billion years is a long, LONG time,” Sachleben wrote in an email, “so no telling what it will be like by then.”
Carroll said that the question of whether the car remains recognizable also depends on who is around to recognize it.
“Remember, our history with tools as a race only goes back about, you know, 2½ million years,” Carroll said, “so what someone would recognize a million years from now if they found it is another story altogether.”
Sachleben was more optimistic, writing, “There is always the possibility that some future, space-venturing car enthusiast may decide Elon’s Roadster would make a nice addition to his/her collection.”