From European Space Agency via Manu Garcia, a friend from IAC: “The limits of the Earth’s atmosphere”

From Manu Garcia, a friend from IAC.

The universe around us.
Astronomy, everything you wanted to know about our local universe and never dared to ask.

ESA Space For Europe Banner

From European Space Agency

20 February, 2019

Igor Baliukin
Space Research Institute
Russian Academy of Science
Moscow, Russia

Jean-Loup Bertaux
Former principal investigator of SWAN
Laboratoire Atmospheres Milieux, Observations Spatiales (LATMOS)
Université de Versailles-Saint-Quentin-en-Yvelines, France

Bernhard Fleck
SOHO project scientist
European Space Agency

Markus Bauer
ESA Science Program Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954

Earth’s atmosphere reaches the Moon and beyond.
The extent of land geocorona. Where the atmosphere of the Earth merges with outer space, there is a cloud of hydrogen atoms called geocorona. A recent discovery based on observations of the Solar and Heliospheric Observatory ESA / NASA SOHO shows that geocorona extends far beyond the orbit of the Moon, reaching up to 630 000 km above the surface of the Earth, or 50 times the diameter of our planet. Note: The illustration is not to scale. Credit: ESA.

The most distant region of our atmosphere extends beyond the lunar orbit, up to twice the distance to our natural satellite.

Thanks to data collected by the Solar and Heliospheric Observatory (SOHO) of ESA / NASA, a recent discovery shows that the gas layer that surrounds the Earth has a radius of 630,000 km, 50 times the diameter of our planet.


“The moon orbits inside the Earth’s atmosphere,” says Igor Baliukin, the Russian Space Research Institute and lead author of the paper presenting the results.

“We were not aware of it until we recover the observations made over two decades ago by SOHO.”

In the region where the atmosphere merges into the outer space, there is a cloud of hydrogen atoms called “geocorona”. One of the satellite instruments, SWAN [no image available], used its sensors to track the signing of hydrogen and accurately detect how far the limit of the geocorona arrived.

These observations could be made only at certain times of the year when the Earth and its geocorona were visible instrument.

In the planets with their exosferas hydrogen, water vapor often seen near the surface. This is what happens on Earth, Mars and Venus.

Jean-Loup Bertaux as, former principal investigator and co-author SWAN explains: “This is particularly interesting when we look for planets with possible water deposits beyond our solar system.”

The first telescope on the Moon, deployed in 1972 by the Apollo astronauts 16 mission captured an image reminiscent of Earth wrapped in geocorona bright ultraviolet light.

“At that time, the astronauts on the lunar surface did not know that they were actually immersed in the outermost layers of the geocorona” says Jean-Loup.

The Sun interacts with the hydrogen atoms through a specific wavelength of the ultraviolet spectrum, called Lyman alpha, these atoms can absorb and emit. As this type of light is absorbed by Earth’s atmosphere, it can only be observed from space.

With its cell uptake of hydrogen, the SWAN instrument could measure light selectively Lyman alpha geocorona and discard the hydrogen atoms located in interplanetary space.

The new study has revealed that sunlight compresses the hydrogen atoms in the geocorona of the day side of the Earth, while producing a denser region on the night side. Hydrogen daytime region of higher density remains rather low, with only 70 atoms per cubic centimeter to 60,000 kilometers from the earth’s surface, and about 0.2 atoms at the distance of the Moon.

“On Earth we would call it empty, so this extra source of hydrogen is not enough to provide space exploration,” Igor added.

The good news is that these particles do not pose a threat to space travelers of future manned missions to orbit the moon.

“There is also ultraviolet radiation associated -we recalls Jean-Loup geocorona Bertaux- since the hydrogen atoms are dispersed in all directions, but the impact on astronauts in orbit would be minimal mole compared to the main radiation source : the Sun”.

The bad news is that the Earth’s future geocorona could interfere with astronomical observations near the moon.

As Jean-Loup warns: “Space telescopes that observe the sky in ultraviolet wavelengths to study the chemical composition of stars and galaxies have to take this into account.”

The power of files.
Print Artist Solar and Heliospheric Observatory ESA / NASA SOHO, with the Sun seen by the extreme ultraviolet telescope satellite images on September 14 , 1999. Credit: Spacecraft: ESA / Medialab ATG; Sun: ESA / NASA SOHO, CC BY-SA 3.0 IGO

Launched in December 1995, the space observatory SOHO has more than two decades studying the sun, from inside its core to the outer corona and solar wind. The satellite orbits in the first Lagrange point (L1), about 1.5 million kilometers from Earth toward the sun.

LaGrange Points map. NASA

Its position is perfect to watch the geocorona from outside. The SWAN instrument SOHO captured images of the Earth and its atmosphere on three occasions between 1996 and 1998.

The team of researchers from Jean-Loup and Igor in Russia decided to recover this data set from the files for analysis. These unique of all the geocorona from SOHO views are now shedding new light on Earth’s atmosphere.

“It is often possible to take advantage of archived data many years and do new science with them -constata Bernhard Fleck, SOHO Project Scientist of ESA-. This finding underscores the value of some data collected over 20 years and the outstanding performance of SOHO “.

More information:
The article ” SWAN / SOHO Lyman-alpha mapping: the Hydrogen geocorona extends well beyond the Moon .” I Baliukin et al, is accepted for publication in Journal of Geophysical Research: Space Physics.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

ESA50 Logo large