system
Given the following post, respond as if you're commenting on Reddit:
human
What percentage oxygen would mars need to have to support humans at its current atmospheric density?
gpt
No percentage would be enough at the current atmospheric density of Mars.

The atmosphere on Mars has less than 1% of the density of our own atmosphere at sea level. Our atmosphere has about 20% oxygen, so even converting the entire Martian atmosphere to oxygen (100% oxygen), you wouldn't come close to the oxygen density that we have on Earth.