As altitude increases in the exosphere, temperature actually increases. This might seem counterintuitive, as we often think of higher altitudes being associated with cooler temperatures, especially in the lower layers of the atmosphere.
The exosphere is the outermost layer of Earth’s atmosphere, extending from about 600 kilometers (373 miles) above sea level to about 10,000 kilometers (6,200 miles). In this region, the air is extremely thin, and the particles are so sparse that they can travel hundreds of kilometers without colliding with one another.
In the exosphere, the temperature can rise significantly due to the absorption of high-energy solar radiation. Most of the molecules in this layer are atomic hydrogen and helium, which can move at very high speeds due to the energy they absorb from the Sun. As they gain energy and speed, it translates to a rise in temperature, even though the few particles present are not dense enough to transmit heat in the way we experience it at lower altitudes.
This phenomenon highlights how temperature doesn’t solely depend on altitude but also on the density and composition of the atmosphere. The concept of temperature is tied to the kinetic energy of particles, and in the exosphere, with its minimal density, the temperature can be misleading if compared directly to what we experience on the surface of the Earth.