re: Landscape of Mars

If a human were exposed to the Martian environment without a spacesuit, they would face several immediate and fatal dangers:
1. Lack of Oxygen – Mars has an atmosphere that is about 95% carbon dioxide with almost no breathable oxygen. A person would lose consciousness in less than 15 seconds due to oxygen deprivation.
2. Low Atmospheric Pressure – Mars’ air pressure is less than 1% of Earth’s, which would cause the water and gases in the body to rapidly expand. This would lead to severe swelling, tissue damage, and almost immediate unconsciousness. Blood would not boil in the veins due to internal pressure, but moisture in soft tissues and lungs would evaporate.
3. Extreme Cold – The average temperature on Mars is about -80°F (-62°C) and can drop much lower at night. A human would freeze within minutes, though other factors would kill them first.
4. Radiation Exposure – Without an atmosphere to protect them, a person would be exposed to high levels of solar and cosmic radiation, though this would not be the immediate cause of death.
5. Boiling Saliva and Tears – Due to the low pressure, saliva and tears would begin to boil off, causing extreme discomfort before unconsciousness.

How Long Would Someone Survive?

A person would likely remain conscious for 10-15 seconds, with death occurring within a minute or two due to asphyxiation and exposure.