- A very thin layer of atoms and molecules, mainly hydrogen and helium, but also some oxygen, nitrogen, and carbon dioxide.

- A very low density of particles, with an average of only a few particles per cubic centimeter.

- A temperature that can vary from extremely hot during the day to very cold at night.

- A very high level of ultraviolet radiation from the Sun, which can be harmful to living organisms.

- A view of the Earth below that would be very different from what we see from the ground, with the atmosphere appearing as a thin blue haze.