Requirements for living in low pressure

While not hard vacuum, the low atmospheric surface pressure on Mars (7 mb) is inimical to Terran biology.

Biological requirements

Known biology has evolved in atmospheric pressures greater than 300 mb. Humans are susceptible to altitude sickness at pressures lower than 700 mb.

Human requirements

At 7 mb, humans require a pressure suit to walk on the surface of Mars.

Questions:

• What is the minimum atmospheric pressure that humans can tolerate?
• What atmospheric pressure is required for humans to be able to walk freely on Mars?

Plant requirements

At 7 mb, plants must be grown in pressurized enclosures.

Questions:

• What is the minimum atmospheric pressure that different plants can tolerate?
• What atmospheric pressure is required for different plants to thrive on Mars?

Engineering requirements

Inhabited structures must be pressurized. Several plans for living on Mars call for regolith to be piled on top of pressurized structures to reduce the strength required for construction materials.