Bird poop and dust could seriously complicate Elon Musk and SpaceX's latest plan to reach Mars, Business Insider
"Dwayne Day*, who helped investigate the loss of NASA's Columbia space shuttle and its crew, said such clogs could come from any number of mundane factors. "What if a bird poops on your rocket and it plugs up a few holes, and then when the thing is returning no coolant comes out of those holes and that section of the vehicle overheats?" he said."
* Dwayne Day is a Senior Program Officer at the National Academy of Science Space and Aeronautics Board. His training is in space policy.