Sustaining life in the harsh vacuum of space and in the low-pressure carbon dioxide Martian atmosphere is challenging and complex. Additionally, there exists a large range of effective temperatures, and the ever-present danger of micrometeorite and space debris impact. On Mars, as on Earth, wide climate differences exist at different points on the planet and temperatures vary by several degrees even from the astronaut's feet to head levels. Astronauts have reported cold discomfort during Extra-vehicular Activities (EVAs), which distracted them from their work.1 The Martian atmosphere is made up of mostly carbon dioxide at a pressure of 0.123 psia (848.1 Pa), far less than the Earth's atmospheric pressure of 14.7 psia (101.4 kPa). These conditions must be quantified so engineers can develop and optimize a space suit system for a given task. Seven primary factors to be considered are listed.