Elon tweeted that Starman's trajectory is going to overshoot Mar's orbit and bring it close to the asteroid belt. Does this mean that Starman is in danger of being crushed by an asteroid??
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asked Feb 7, 2018 at 16:01
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2$\begingroup$ [Insert "Space is huge" quote from The Hitchhiker's Guide to the Galaxy here] $\endgroup$– MarkCommented Feb 10, 2018 at 0:13
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$\begingroup$ in "any" danger... Yes, quite certainly. How likely though? 1/100000 per year, maybe? Less? The asteroid belt is pretty much perfectly empty space. (low earth orbit is much, much,much,much more cluttered) $\endgroup$– CuteKItty_pleaseStopBArkingCommented Apr 21, 2021 at 12:50
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2 Answers
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Is Starman/Roadster in any danger of asteroid belt?
Honestly? No.
The Asteroid belt does contain lots of asteroids. But this is deep space. These things are not close together in any sense.
Think of it this way: If Starman had been set adrift on the Pacific Ocean, how likely would he be to collide with another ship? Pretty low? The ships on the ocean are many orders of magnitude closer together than the rocks floating around the asteroid belt.
Starman will be phenomenally lucky if he even comes within a few hundred thousand miles of an asteroid, let alone hitting one.
We've sent a number of space probes through the asteroid belt in the past, and none of them have had any trouble at all (the Dawn probe even navigated within the belt to explore Vesta and Ceres). This isn't a place like the asteroid field in Star Wars, or the Asteroids video game. There is a lot of empty space out there.
That said, we honestly don't know of all the rocks that are out there, so it is possible that Starman could encounter one of them. But it is incredibly unlikely.
You might also be interested in this question which asks about the frequency of asteroids colliding with each other.
Another relevant article on Spaceflight Now explains that the in the very long term, the likely fate of the roadster is either to fall into the sun due to orbital decay, or to be ejected from the solar system due to the influence of Jupiter.
[Edit] Final update that I'm going to make here. There's a study been done that tries to calculate the orbit and make long term predictions.
The first close encounter with the Earth will occur in 2091. The repeated encounters lead to a random walk that eventually causes close encounters with other terrestrial planets and the Sun. ... we estimate the probability of a collision with Earth and Venus over the next one million years to be 6% and 2.5%, respectively.
arXiv:1802.04718
So yeah, general consensus is no danger from asteroids. :-)
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3$\begingroup$ If Starman had been set adrift in the Pacific Ocean, with ships continuing to sail as they do now for one billion years, then the likelihood of a collision would be huge. Space may be big, but one billion years is a long time. $\endgroup$– gerritCommented Feb 7, 2018 at 16:37
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$\begingroup$ @Simba is there a formula to calculate the likelihood of colliding with an asteroid for a given amount of time? Gerrit raises a good point that Starman's odds of survival might be great, but he will be playing those odds for a very long time. $\endgroup$ Commented Feb 7, 2018 at 16:50
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$\begingroup$ The question didn't specify a time frame, but I suspect the OP wasn't thinking about it in the extreme long term. For timescales that matter to us mortals, the Tesla is not in an realistic danger of a collision. For longer term timescales, no I'm not aware of a formula, but Gerrit's point is correct; the longer it's up there, the greater its chance of hitting something. All things being equal, it will hit something eventually, just like if I keep playing the lottery I will win eventually. $\endgroup$– SimbaCommented Feb 7, 2018 at 16:59
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2$\begingroup$ But I would say that it's far more likely to collide with Earth than an asteroid. That won't happen for a long time either, but Earth is a much bigger target than any asteroid, and the Tesla will be intersecting our orbit on a regular basis. $\endgroup$– SimbaCommented Feb 7, 2018 at 17:03
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$\begingroup$ @Simba just for clarification, I AM the OP, and obviously I'm thinking long term. $\endgroup$ Commented Feb 7, 2018 at 18:45
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As Simba's answer explained, the probability of a spacecraft accidentally colliding with an asteroid is very low. On average, asteroids in the Main Belt are hundreds of thousands of kilometers apart. If you could stand on an asteroid, you probably wouldn't even be able to see another asteroid with your unaided eyes. (The exception to this is when an asteroid has one or more satellites, like 87 Sylvia and its two moonlets.)
Alan Stern, the principal investigator for New Horizons, made some helpful calculations for the odds of an asteroid colliding with NH as it passed through the main belt:
Fortunately, the asteroid belt is so huge that, despite its large population of small bodies, the chance of running into one is almost vanishingly small - far less than one in one billion. That means that if you want to actually come close enough to an asteroid to make detailed studies of it, you have to aim for a specific asteroid.
Despite how they're portrayed in movies, asteroids aren't really space travel hazards. If you want to hit one, you probably have to be intentional about it.
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2$\begingroup$ "Despite how they're portrayed in movies" or video games $\endgroup$ Commented Apr 21, 2021 at 2:55