https://twitter.com/AscendingNode/status/961086031784235008
I realize deep space collision risk is very low. I saw a talk with Alan Stern about New Horizons where he answers someone's question about collision avoidance in the asteroid belt that on a trip out to Pluto you are unlikely to encounter anything larger than a grain of sand. But rather than acting annoyed with the person who questioned him, he answered the question well, and I still remember his answer. And let use not forget that space exploration has ethically questionable choices and "improbable" events occur in the past (e.g., Laika, artificial radiation belts from nukes, debris from an RF reflecting foil cloud).
But in any case, I'm happy with with earnest questions about math/science. What's boring and distracting are these expressions of concern about rule violations. Consider: would the original comment of NathanKP have been popular if he asked "I wonder what the chances are that the Tesla will collide with an asteroid?" No. Maybe someone would have quickly pointed to a calculation or estimate, but it would't be at the top of the thread without the emotional appeal that someone somewhere might be breaking a rule.
As it turns out, the difference in probability between the things you mention and interplanetary collisions is astronomical -- like dozens or more orders of magnitude -- and a minute of Googling shows that NASA frequently satisfies the planetary protection rules by ensuring that non-sanitized parts of inbound spacecraft miss the planet on the first pass (even though they will in principle be circling in the same general orbit for a billion years).