SpaceX CEO Elon Musk grabbed the world’s attention last week after launching his Tesla Roadster into space. But his publicity stunt has a half-life way beyond even what he could imagine—the Roadster should continue to orbit through the solar system, perhaps slightly battered by micrometeorites, for a few tens of millions of years. Now, a group of researchers specializing in orbital dynamics has analyzed the car’s orbit for the next few million years. And although it’s impossible to map it out precisely, there is a small chance that one day it could return and crash into Earth. But don’t panic: That chance is just 6% over a million years, and it would likely burn up as it entered the atmosphere.
Hanno Rein of the University of Toronto in Canada and his colleagues regularly model the motions of planets and exoplanets. “We have all the software ready, and when we saw the launch last week we thought, ‘Let’s see what happens.’ So we ran the [Tesla’s] orbit forward for several million years,” he says. The Falcon Heavy rocket from SpaceX propelled the car out toward Mars, but the sun’s gravity will bring it swinging in again some months from now in an elliptical orbit, so it will repeatedly cross the orbits of Mars, Earth, and Venus until it sustains a fatal accident. Rein says the car’s predicted orbit is similar to the many near-Earth asteroids that drift throughout the inner solar system. Other researchers have charted the fluctuating brightness of the car in space to calculate that it is rotating roughly once every 5 minutes.
The Roadster’s first close encounter with Earth will be in 2091—the first of many in the millennia to come. But because tiny differences in trajectory before an encounter lead to huge differences afterward, the orbit is essentially chaotic and impossible to map out with certainty.
By tweaking orbital parameters and running their model repeatedly, the team could make some statistical predictions about the car’s future path. Over a million years, the Tesla has a 6% probability of an Earth collision and a 2.5% chance of crashing on Venus, the researchers reported yesterday on the physics preprint server arXiv. After 3 million years, the odds of an Earth crash rise to 10%. In the longer term, Rein estimates that the Roadster has a 50% chance of lasting a few tens of millions of years. Unclear is whether it will end its journey as debris on some planetary surface or as a blazing hot ball of metal plunging into the sun.
If it does come crashing into Earth, Musk doesn’t need to worry about his third party insurance. “It will either burn up or maybe one component will reach the surface,” Rein says. “There is no risk to health and safety whatsoever.”