Surprise: Earths atmosphere extends far beyond the Moon

From the data collected by the Soho mission, a Franco-Russian team calculated that the atmosphere extended up to 630,000 kilometers beyond the Earth! It would, therefore, encompass the Moon. Jean-Loup Bertaux, director of research emeritus at the CNRS and former head of the photometer who acquired the data in question, explains this rather surprising discovery.

While the space boundary was arbitrarily set at 80 and 100 kilometers above sea level, an international team including two CNRS researchers has just discovered that our atmosphere extends up to 630,000 kilometers, almost twice as much. far than the Moon, six times farther than the limit so far supposed! The data recorded by the Swan photometer on board the space-based observatory Soho of Sun, almost twenty years ago (between 1996 and 1998) allowed the French-Russian team led by Jean-Loup Bertaux, research director emeritus at the CNRS, to calculate that the geocorona extended up to twice the distance Earth-Moon. The study has just been published in the journal  Journal of Geophysical Research.

Did you know?

Set at 100 kilometers above sea level, the Kármán line is recognized by the International Aeronautical Federation (FAI). The second arbitrary boundary is located 20 kilometers lower (80 km altitude). She is recognized by NASA and the US Air Force.

A rather surprising discovery that also means that the atmosphere of "  the Earth is much wider than the thin blue ring that surrounds our planet seen from space  ", says Jean-Loup Bertaux, former head of the Swan photometer. Beyond that circle, she "  continues to be" melt "into space, is ending in a vast cloud of atoms of hydrogen which is called geocorona  " explains the scientist also a senior researcher of the Atmosphere Laboratory, media, space observations (Latmos).
That said, at this distance, the atmosphere has nothing to do with the one that allows us to live on Earth. In reality, the Earth's atmosphere quickly becomes extremely tenuous: "  At  60,000km, it is already composed of only 70 atoms per cubic centimeter ... and halfway, at the Moon, only 0, 2 atoms per cubic centimeter. To say the void ... or almost. Do not imagine being able to breathe air on the surface of the Moon!

A geocorona who will not prevent the good progress of human activities nearby and on the Moon

But it should be known that these particles, essentially hydrogen atoms, pose no threat to manned flights to the moon, or to astronauts aboard the lunar outpost that will be built close to the moon. Moon on the horizon 2025. As for those who will be active on the lunar soil, the risk is also marginal. They will especially have to worry about the Sun, the main source of radiation that could affect them.

On the other hand, this discovery is "   a step further towards a refinement of the measurements  " and could serve to "  correct the errors of observation of the sky in the ultraviolet  ". Indeed, the hydrogen atoms emit ultraviolet radiation that could parasitize future astronomical observations conducted in the geocorona. Whether on the Moon or in its vicinity, "  the telescopes space  studying the  chemical composition  of stars and galaxies should consider these interferences  ."

Finally, this discovery also has a playful side. In addition to knowing today that the Moon is moving in Geocouronne, it is amusing to think that the "Apollo astronauts on the surface of the Moon did not know that they were bathing in the atmosphere of the Earth! "

WHAT YOU MUST REMEMBER

• The atmosphere of the Earth extends far beyond what was thought.
• An international team has calculated that it extends up to 630,000 kilometers from the Earth, encompassing the Moon.
• Two French researchers participated in this study, including Jean-Loup Bertaux, former head of the instrument, to whom we owe the data that allowed this calculation.