Both NASA and the United States Air Force recognize approximately 80 kilometers above the Earth’s surface as the so-called ‘boundary’ after which you enter outer space. But the topic on where Earth’s atmosphere ends and where space begins has been long debated among scientists. And, spoiler alert, we still don’t have an official designation.
The Earth’s atmosphere is comprised of various layers, including the Troposphere, the Stratosphere, the Mesosphere, the Thermosphere, and the Exosphere. The first four are somewhat easy to identify, in that:
On the other hand, the Exosphere is much more challenging to define, because particles from the Earth’s atmosphere tend to wander somewhat far into outer space. Initially, it was thought that these particles wandered up to 200,000 kilometers into outer space, but new measurements obtained with the Solar Wind Anisotropies instrument (SWAN) suggest that the exosphere might extend up to 630,000 kilometers into space.
The new data suggests that the Earth’s atmosphere is much larger than initially thought, and perhaps more importantly, that even the Moon resides in the Earth’s massive atmosphere.
Given the latest findings, one might even say that no human as ever left Earth’s atmosphere, and that may never change until astronauts venture to another planet, such as Mars, to conduct scientific exploration elsewhere in the solar system.
Much of the world continues to debate where the Earth’s atmosphere ends and where space begins due to the lack of an official standard concerning the matter, but perhaps the latest findings will help bring closure to that debate once and for all.