Surprise! Earth's Atmosphere Extends Far Beyond the Moon

"A cloud of hydrogen atoms called the geocorona exists where Earth’s atmosphere bleeds into outer space. New research suggests that the cloud extends far beyond the orbit of the moon, reaching up to 630,000 kilometers from Earth surface."

Earth air stretch way out into space, very far beyond the moon's orbit, a brand new study suggests.

Earth's 'geocorona' - a tenuous cloud of H atoms - extends up to 630,000 kilometers in space, consistent with the new research. For perspective: The moon orbits Earth at the average distance of 384,600 km.

According to led author Igor Baliukin, of Russia's space research Institute, the moon flies through Earth's atmosphere. We weren't conscious of it till we dusted off observations done over 20 years past by the SOHO rocket.

Solar and Heliospheric Observatory(SOHO) is a joint European-NASA probe that launched in December 1995 to study the weather of the sun and space.

Balkin and his team analyzed the data gathered by SOHO's Solar Wind Anisotropies Instrument (SWAN) specifically, measurement of the type of ultraviolet light called Lyman alpha radiation. Sunlight interacts with the geocorona H atoms at the Lyman alpha wavelength which get blocked by the atmosphere of Earth and thus must be observed from space. 

This work allowed the team to map the geocorona's existence and get a handle on the region's density. They observed that the geocorona is denser on Earth's dayside, due to compression from solar radiation. But denser is a relative term as There are just 70 hydrogen atoms/cm^3 (or 0.06 per cubic inches) at the height of 60,000 km on the dayside and a mere 0.2 atoms/cm^3 at the moon's distance, according to the new study.

Balkin said, "On Earth, we would call it to vacuum, so this extra source of hydrogen is not enough signatures to facilitate space exploration,".

Image Source: Nasa

Scientists had already known that Earth possesses geocorona hydrogen atoms; indeed, NASA's Apollo 16 mission photographed this from the moon in 1972. But the geocorona's reach was supposed to be much limited.

According to co-author Jean-Loup Bertaux, former SWAN principal investigator "At that time, the astronauts on the moon surface didn't know that they were actually embedded in the outskirts of the geocorona,".

The new study, which was published last week in the Geophysical Research: Space Physics Journal, could have applications beyond Earth's backyard. According to the researchers, the planets containing hydrogen in their atmosphere often have water (water vapor) in their surface.

According to Bertaux, "This is the especially interesting fact when searching for planets with the potential of water reservoirs beyond our solar system,".

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