I'm currently building a planet that I want to have both alien life forms and humans. It has the following traits:
Humans migrated from Earth a long time ago, but only landed on the planet 24 years ago.
The planet has Earth-like life and humans on it together.
The planet is about twice as big as the Earth in radius, and is 4 times as massive (I think that's the term in astronomy for having more mass...?), and has 1G gravity (To Earth).
The planet has 2 stars:
An F-type star of 1.2 solar masses with about 2.3 billion years left as of current times
A K-type star of 0.4 solar masses
The planet orbits the two stars at about 1.6 AU on average.
The planet has 2 moons:
1 around 80% the size of the Earth, orbiting at 238,900 miles away on average.
1 28% the size of Earth, orbiting at about 72,527 miles away on average.
- Humans to be able to live on the surface naturally.
Difficulties in Living
My planet has:
A global temperature is around 23 Celsius (78 Fahrenheit), with the poles having a typical average of about 10 Celsius (50 Fahrenheit), and the hottest regions (Mostly sun-scorched deserts) having an average of about 54 Celsius (129 Fahrenheit).
An atmospheric pressure of 144% Earth's at sea level
- 32% oxygen (a bit over 50% more than modern Earth, but a bit more than 21% less than the Carboniferous period)
- 67% nitrogen
- 1% other gases, with atmospheric carbon dioxide level at about 1,600 ppm (In the range of the Cretaceous (1,000-2,000 ppm)). T
The temperature and atmospheric composition came to their current values about 12 million years ago, so life on the planet has adapted.
I don't care whether humans can breathe on the planet without an oxygen mask. They came well after life evolved, so their ability to breathe isn't my problem, and they have the technology to make their own in my world anyway.
What I want to know is whether humans could live out in the open on this world with nothing more than an oxygen mask. A major concern of mine is the atmosphere, which is, at sea level, about 130% thicker than Earth's, and the temperature. This temperature is around the normal average temperature of Earth during the Paleocene-Eocene Thermal Maximum (PETM), so Earth-like life could survive, and I don't care about ice caps. However, I wanted to know whether humans could survive with only an oxygen mask.
Things To Consider
The atmosphere is thicker, but according to this question's answer, humans could theoretically survive up to 4 times Earth's atmospheric pressure.
The oxygen levels are likely too high (By how much oxygen %, I don't know).
Maybe the temperatures make the equator too hot for humans to survive in the open all year round, so humans might have to settle more at the poles.
The biochemistry is similar to Earth's, meaning that humans should be able to consume food safely (For those of you who don't know, Earth biochemistry is almost all left-handed amino acids, and they cannot be swapped for right-handed ones).
Could humans survive on this planet in to open with only an oxygen mask?