Strange But True: Earth's Invisible Halo Nearly Reaches The Moon

A new mission from NASA has just launched to study and photograph this strange quirk of the Earth-Sun system.

First image of Earth's geocorona | G. Carruthers (NRL) et al. / Far UV Camera / NASA / Apollo 16

The invisible halo surrounding Earth is created by faint light given off by our planet's outermost layer as it interacts with the Sun. It's called the geocorona and the reason why we can't naturally see it with our eyes is because the halo is ultraviolet light. The exosphere, our atmosphere’s outermost layer, begins about 300 miles up and it's seen only as a faint halo of ultraviolet light.

A scientist and engineer named Dr. George Carruthers decided to take a look at it in the early 1970s. Carutthers developed an ultraviolet camera that was placed on the Moon (who knew?) in April 1972 by Apollo 16 astronauts, giving humanity its first glimpse of the geocorona. Now, scientists think the exosphere could stretch halfway to the Moon - at least.

There are two main reasons why NASA wants to learn more about the geocorona: first, protecting astronauts. That's because as eruptions from the Sun hit our planet, they smash into the exosphere first. That sets off a chain reaction of events that can result in dangerous space weather, which is the term given to the effects of the Sun's powerful influence across the Solar System.

Secondly, it should help us learn more about distant planets. Understanding in greater detail how solar storms cause hydrogen to escape through our exosphere could help scientists learn more about why Earth retains water while other planets don't. That could help us find and study planets beyond our Solar System - known as exoplanets - where the same thing happens.

OGN will keep you posted.

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