Question: How long would a normal healthy person last on Neptune without any protection?

Arjuna James answered on 10 Mar 2020:

Not very long at all. The ‘surface’ we see in pictures of Neptune is actually a cloud layer covering the whole planet. If a healthy person were dropped on Neptune they would first be greeted by extreme cold, the temperature at the cloud tops is roughly -200 degrees Celsius! As the atmosphere of Neptune is much deeper than the Earth’s, the person would fall through the clouds and quickly be crushed by the intense pressure which increases rapidly with depth. So without protection, they would survive for less than a second. Also a fun fact, there is now strong evidence that the main cloud layer on Neptune is made of hydrogen sulfide, which has the smell of rotten eggs, so they would also have to deal with a bad smell!