system
Given the following post, respond as if you're commenting on Reddit:
human
What would happen if you stepped onto the Martian surface without a spacesuit? How quickly would you die, and what symptoms would you experience?
gpt
The current atmospheric pressure is about 1% of that of Earth, so for all intents and purposes this can be treated as a vacuum for the effects on the human body.

Air will briefly rush out of your orifices, mostly your throat. If you'd been holding your breath this will damage your throat. You'd feel bloated, and your ears might start bleeding.

The small amount of atmosphere might make you feel very cold, depending on your clothing.

Within about 10 seconds you'd lose consciousness because your brains shuts down most higher thought processes due to lack of oxygen.

Within a few minutes irreversible brain damage would occur, and not much later you'd be dead.

TL;DR: You should not walk on Mars without a suit, it's lethal.