Earth's atmosphere stretches out to the moon – and beyond

February 20, 2019 by Claudia Mignone, American Geophysical Union
The extent of Earth’s geocorona. Where Earth’s atmosphere merges into outer space, there is a cloud of hydrogen atoms called the geocorona. Note: the illustration is not to scale. Credit: ESA

The gaseous layer that wraps around Earth reaches up to 630,000 kilometers away, or 50 times the diameter of our planet, according to a new study based on observations by the ESA/NASA Solar and Heliospheric Observatory, SOHO, and published in AGU's Journal of Geophysical Research: Space Physics.

"The moon flies through Earth's atmosphere," says Igor Baliukin of Russia's Space Research Institute, lead author of the paper presenting the results. "We were not aware of it until we dusted off observations made over two decades ago by the SOHO spacecraft."

Where our atmosphere merges into , there is a cloud of atoms called the geocorona. One of the spacecraft instruments, SWAN, used its sensitive sensors to trace the hydrogen signature and precisely detect how far the very outskirts of the geocorona are. These observations could be done only at certain times of the year, when the Earth and its geocorona came into view for SWAN.

For planets with hydrogen in their exospheres, water vapor is often seen closer to their surface. That is the case for Earth, Mars and Venus.

"This is especially interesting when looking for planets with potential reservoirs of water beyond our solar system," explains Jean-Loup Bertaux, co-author and former principal investigator of SWAN.

The first telescope on the moon, placed by Apollo 16 astronauts in 1972, captured an evocative image of the geocorona surrounding Earth and glowing brightly in ultraviolet light.

"At that time, the astronauts on the did not know that they were actually embedded in the outskirts of the geocorona," says Jean-Loup.

Earth’s geocorona from the moon. The Earth and its hydrogen envelope, or geocorona, as seen from the moon. This ultraviolet picture was taken in 1972 with a camera operated by Apollo 16 astronauts on the Moon. Credit: NASA
Cloud of hydrogen

The sun interacts with hydrogen atoms through a particular wavelength of called Lyman-alpha, which the atoms can both absorb and emit. Since this type of light is absorbed by Earth's atmosphere, it can only be observed from .

Thanks to its hydrogen absorption cell, the SWAN instrument could selectively measure the Lyman-alpha light from the geocorona and discard hydrogen atoms further out in interplanetary space.

The new study revealed that sunlight compresses hydrogen atoms in the geocorona on Earth's dayside, and also produces a region of enhanced density on the night side. The denser dayside region of hydrogen is still rather sparse, with just 70 atoms per cubic centimeter at 60,000 kilometers above Earth's surface, and about 0.2 atoms at the moon's distance.

"On Earth we would call it vacuum, so this extra source of hydrogen is not significant enough to facilitate space exploration," says Igor. The good news is that these particles do not pose any threat for space travelers on future crewed missions orbiting the moon.

"There is also associated to the geocorona, as the scatter sunlight in all directions, but the impact on astronauts in would be negligible compared to the main source of radiation – the sun," says Jean-Loup Bertaux.

On the down side, the Earth's geocorona could interfere with future astronomical observations performed in the vicinity of the moon.

SOHO observation of the geocorona. The intensity of hydrogen atom emission in the outermost part of Earth’s atmosphere, the geocorona, as measured by the SWAN instrument on board the ESA/NASA Solar and Heliospheric Observatory, SOHO. Low intensity is indicated in blue, high intensity in red. The data revealed that the geocorona extends well beyond the orbit of the Moon, reaching up to 630,000 kilometers above Earth’s surface, or 50 times the diameter of our planet. Earth is located at the centre of the white area, too small to be visible at this scale; the extent of the Moon’s orbit around Earth is indicated as a dotted ellipse for reference. Credit: ESA/NASA/SOHO/SWAN; I. Baliukin et al (2019)
"Space telescopes observing the sky in ultraviolet wavelengths to study the chemical composition of stars and galaxies would need to take this into account," adds Jean-Loup.

The power of archives

Launched in December 1995, the SOHO space observatory has been studying the sun, from its deep core to the outer corona and the solar wind, for over two decades. The satellite orbits around the first Lagrange point (L1), some 1.5 million kilometers from Earth towards the sun.

This location is a good vantage point to observe the geocorona from outside. SOHO's SWAN instrument imaged Earth and its extended atmosphere on three occasions between 1996 and 1998.

Jean-Loup and Igor's research team in Russia decided to retrieve this data set from the archives for further analysis. These unique views of the whole geocorona as seen from SOHO are now shedding new light on Earth's atmosphere.

"Data archived many years ago can often be exploited for new science," says Bernhard Fleck, ESA SOHO project scientist. "This discovery highlights the value of data collected over 20 years ago and the exceptional performance of SOHO."

Explore further: NASA's MAVEN spacecraft finds that 'stolen' electrons enable unusual aurora on Mars

More information: I. I. Baliukin et al. SWAN/SOHO Lyman-α mapping: the Hydrogen Geocorona Extends Well Beyond The Moon, Journal of Geophysical Research: Space Physics (2019). DOI: 10.1029/2018JA026136

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18 comments

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cantdrive85
1.9 / 5 (18) Feb 20, 2019
The idea that Earth's atmosphere is held in place by gravity is being shown to be a very tenuous guess.
MrBojangles
4.3 / 5 (11) Feb 20, 2019
You're right, it's only a matter of time before the plasma ignoramus's who control the world accidentally let the truth slip out. Then everyone will know that everything is caused by electricity. Ben Franklin tried to warn us, but we didn't listen.
Mark Thomas
4.6 / 5 (10) Feb 20, 2019
The idea that Earth's atmosphere is held in place by gravity is being shown to be a very tenuous guess.


I am curious, what do you do to earn a living? Have you ever graduated from any school at any level? Do you live independently? Where?
jonesdave
4.4 / 5 (13) Feb 20, 2019
The idea that Earth's atmosphere is held in place by gravity is being shown to be a very tenuous guess.


Yeah, right! Lol. Do please tell us - what is holding neutral 02 and N2, for instance, in place? Why is there very little H2 or He? Why has Jupiter got a massive atmosphere? And Mars hasn't?
theredpill
1.4 / 5 (10) Feb 20, 2019
"I am curious, what do you do to earn a living? Have you ever graduated from any school at any level? Do you live independently? Where?"

If it is gravity keeping our atmosphere in place, and a portion of our atmosphere extends well out past the moons, where is the moons gravitationally bound atmosphere that is 1/6 the density of ours....you know, linear relationships and all.

Also, while you are at it, a lot of really confused PHD's also want to know how Venusian gravity, being slightly less than that of earths, keeps the surface pressure at 90 X earths atmosphere....cause atmospheres are gravitationally bound right?

It's funny that you clearly only thought of 2 variables, earth and gravity, when he posted that and you decided to try to mock him....but then again you are a climate "expert" too right? LMAO

RealityCheck
3.7 / 5 (6) Feb 20, 2019
@theredpill.

Careful, mate; you also seem to be too eager to deride the derider, and so miss some salient considerations, such as the molecular weight of Venuses' atmospheric constituents and the way the many constituents are entrained/interacting so as to remain in the atmospheric column before 'raining out' as the observed 'Sulphuric Acid Rain' and other compounds that are much more heavy than free hydrogen/helium atoms. As for why the Moon doesn't have an atmosphere, you miss the fact that the Moon doesn't have a magnetic field 'cocoon' like Earth which redirects both solar-sourced ions/electrons and Earth-system 'escapee' ions/electrons back to the body generating the magnetic field 'cocoon'. Its all very complex/hybrid dynamics involved, 'anchored' by the relevant 'locally dominant' Gravitating AND Magnetic body, as just explained. If you want to discourage derision from others, then try to be more 'measured' and informed in your own commentary. Good luck. :)
Mark Thomas
4.3 / 5 (11) Feb 20, 2019
theredpill is a Scumbag Denier who misrepresents everything scientific and has no integrity whatsoever. He was educated at Scumbag University and graduated as Scumbag Denier (with dishonors).

https://phys.org/...ies.html

I was actually curious about cantdrive85's situation, but you I expect are in some boiler room trying to make a shitty living.
granville583762
5 / 5 (4) Feb 20, 2019
Is it taking this tenuous atmosphere in solar orbit or is the Earth continuously losing its atmosphere
and what role has the Earth's magnetic field in retaining this tenuous atmosphere
and
if so
that would mean the Moon if it had a magnetic field
could
Also retain this atmosphere
MrBojangles
4.3 / 5 (11) Feb 20, 2019
I saw RCs response to theredpill and curiosity got the best of me, had to briefly take him off ignore.

If it is gravity keeping our atmosphere in place, and a portion of our atmosphere extends well out past the moons, where is the moons gravitationally bound atmosphere that is 1/6 the density of ours....


Pure gold.

Also, while you are at it, a lot of really confused PHD's also want to know how Venusian gravity, being slightly less than that of earths, keeps the surface pressure at 90 X earths atmosphere....cause atmospheres are gravitationally bound right?


I assume these really confused "PHD's" are David Talbott and Wallace Thornhill.

Remember that PV=nRT equation I showed you? Remember how you mocked me?
You really ought to study it, it will help you understand the relationship between pressure and temperature.
Pull your head out of your arse for just a few moments and educate yourself.
cantdrive85
1.7 / 5 (12) Feb 20, 2019
This is likely, more or less, the extent of the Earth's electric field. And yes jonesdumb, an electromagnetic field can hold neutrals.
theredpill
1.8 / 5 (5) Feb 21, 2019
@RC
"As for why the Moon doesn't have an atmosphere, you miss the fact that the Moon doesn't have a magnetic field 'cocoon' like Earth which redirects both solar-sourced ions/electrons and Earth-system 'escapee' ions/electrons"

Um no...the person who thinks gravity keeps the atmosphere in place misses the above...it is why I said what I did and started my comment with the word "if".

" Its all very complex/hybrid dynamics involved, 'anchored' by the relevant 'locally dominant' Gravitating AND Magnetic body, as just explained. If you want to discourage derision from others, then try to be more 'measured' and informed in your own commentary. Good luck. :)"

Good speech, but you missed my the point entirely as noted in the first portion of my response to you.

"I was actually curious about cantdrive85's situation," LMAO...he's single...go for it!!

antigoracle
3 / 5 (6) Feb 21, 2019
This is likely, more or less, the extent of the Earth's electric field. And yes jonesdumb, an electromagnetic field can hold neutrals.

jonesdave is just another sock puppet of Da Schitts. He's just too stupid to be only one "person" on this forum, hence his many sock puppets.
The fact that the atmosphere can reach that far out and not be dissipated by the solar wind, makes for a compelling argument, that something other than gravity is holding it.
jonesdave
4 / 5 (4) Feb 21, 2019
This is likely, more or less, the extent of the Earth's electric field. And yes jonesdumb, an electromagnetic field can hold neutrals.

jonesdave is just another sock puppet of Da Schitts. He's just too stupid to be only one "person" on this forum, hence his many sock puppets.
The fact that the atmosphere can reach that far out and not be dissipated by the solar wind, makes for a compelling argument, that something other than gravity is holding it.


Lol. Idiot.
jonesdave
4 / 5 (4) Feb 21, 2019
This is likely, more or less, the extent of the Earth's electric field. And yes jonesdumb, an electromagnetic field can hold neutrals.


More crap from the crapster in chief. An electric field is having no effect on neutral H, dumbarse. The solar wind carries an electric field. Moving outwards. Through this neutral H. What is happening, thicko? Talk about stupid.
jonesdave
4.2 / 5 (5) Feb 21, 2019
Also, while you are at it, a lot of really confused PHD's also want to know how Venusian gravity, being slightly less than that of earths, keeps the surface pressure at 90 X earths atmosphere....cause atmospheres are gravitationally bound right?


No way has this idiot got a PhD in anything! Little science lesson for the truly stupid;

Molecular mass of CO2 in Venusian atmosphere (and anywhere else); 44
Molecular mass of H; 1

Venus carbon budget is similar to Earth's. However, most of its is in the atmosphere. And the planet is massive enough to hold onto it. Not hard, was it? Go get an education.

jonesdave
4.2 / 5 (5) Feb 21, 2019
The fact that the atmosphere can reach that far out and not be dissipated by the solar wind, makes for a compelling argument, that something other than gravity is holding it.


This is a collisionless plasma, dumbo. The solar wind is doing nothing to neutral H. It will only pick it up if it becomes ionised due to mostly photo-ionisation.

jonesdave
5 / 5 (4) Feb 21, 2019
RealityCheck
2.3 / 5 (3) Feb 27, 2019
@theredpill.
@RC.
As for why the Moon doesn't have an atmosphere, you miss the fact that the Moon doesn't have a magnetic field 'cocoon' like Earth which redirects both solar-sourced ions/electrons and Earth-system 'escapee' ions/electrons"
Um no...the person who thinks gravity keeps the atmosphere in place misses the above....
Yes, my apologies, mate, re that Moon point. When I wrote that I was thinking of the overall complex/hybrid situations which determine whether bodies retain/lose atmospheres. I understood what you said to your interlocutor re that Moon case but I wrote my response under the overall context and failed to clearly acknowledge your point as made to your interlocutor. Also my apologies for being so tardy in replying; been busy elsewhere. Cheers. :)

ps: re this:
@Mark Thomas.
I was actually curious about cantdrive85's situation
LMAO...he's single...go for it!!
Not 'my cup of tea', mate! I'll leave @Mark Thomas to speak for himself. :)

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