Eksosfääriä

Eksosfääriä, also known as the exosphere, is the outermost layer of Earth's atmosphere. It begins at the upper boundary of the thermosphere and extends outwards into space. Unlike the lower atmospheric layers, the exosphere is characterized by extremely low density, where atmospheric particles are so widely spaced that they can travel long distances without colliding with each other.

The exosphere is essentially a transition zone between Earth's atmosphere and interplanetary space. Its altitude is not precisely defined but is generally considered to start around 500 to 1,000 kilometers (310 to 620 miles) above the Earth's surface and extend to about 10,000 kilometers (6,200 miles). Within this region, atoms and molecules, primarily hydrogen and helium, are so spread out that they are influenced more by the Earth's gravitational pull than by collisions with other particles. Some particles can escape Earth's gravity altogether and drift into space.

Due to the extremely low density, the exosphere has no discernible temperature in the way that lower atmospheric layers do. However, the kinetic energy of the sparse particles is high. Satellites, including the International Space Station, orbit within or pass through parts of the exosphere. The exosphere plays a role in the loss of light atmospheric gases from Earth's atmosphere into space over geological timescales.