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Earth's Atmosphere Extends Much Farther Than Previously Thought (newatlas.com)
Contrary to general belief that Earth's atmosphere stops a bit over 62 miles from the surface, a new study based on observations made over two decades ago by the joint US-European Solar and Heliospheric Observatory (SOHO) satellite shows that it actually extends as far 391,000 miles (630,000 km) or 50 times the Earth's diameter. This makes the Moon a very high altitude aircraft. From a report: Launched on December 2, 1995 atop an Atlas IIAS launcher from Cape Canaveral Air Force Station in Florida, SOHO is parked in the first Lagrange point (L1) 930,000 miles (1.5 million km) from Earth where it has carried out studies of the Sun and the solar winds, and will continue to do so until at least 2020. From this vantage point, the observatory's Solar Wind Anisotropie (SWAN) instrument is able to measure the presence of hydrogen by looking at the Lyman-alpha line in the solar spectrum. And what works for the Sun, works for Earth. By turning SWAN on the Earth at the right times of the year, SOHO was able to detect hydrogen atoms from the atmosphere and measure how far out they extend into what space scientists call the geocorona. While the existence of the geocorona is well known -- the telescope set up by the Apollo 16 astronauts on the Moon even photographed it -- no one was sure how far out it reaches until now.
By looking at data collected by SOHO in the mid 1990s, scientists from Russia's Space Research Institute and elsewhere were able to work out the extent and density of the geocorona. What they found was that sunlight on the day side of the Earth compresses the hydrogen until it reaches a density of 70 atoms per cubic cm at an altitude of 37,000 miles (60,000 km), and on the night side it can expand out until it has a density of only 0.2 atoms per cubic cm at the distance of the Moon's orbit. According to the study leader Igor Baliukin, the geocorona is so tenuous that it poses no hazard to astronauts or spacecraft.
By looking at data collected by SOHO in the mid 1990s, scientists from Russia's Space Research Institute and elsewhere were able to work out the extent and density of the geocorona. What they found was that sunlight on the day side of the Earth compresses the hydrogen until it reaches a density of 70 atoms per cubic cm at an altitude of 37,000 miles (60,000 km), and on the night side it can expand out until it has a density of only 0.2 atoms per cubic cm at the distance of the Moon's orbit. According to the study leader Igor Baliukin, the geocorona is so tenuous that it poses no hazard to astronauts or spacecraft.
So a lot of those astronauts who thought they went into outer space? Not so much.
You mean the atmosphere doesn't end at exactly 100 Kilometers, I'm shocked!
Or more likely it's obvious that an arbitrary number had to be picked because it's a gradient and 100km was a pretty good number for the purpose of picking an arbitrary number where stuff was thin enough to be outer space.
Wow, sent an e-mail as suggested when clicking on "use classic" banner, and got a fast response that addressed my msg
I wonder if molecules that far out are "lost" and simply on their way out of the earth's gravitational influence, or if they are actually a stable part of the atmosphere. If they are a stable part of the atmosphere then they can eventually work their way back to the thicker atmosphere and then down to the surface (in the form of recombining into H20 for example). So we could be drinking water with hydrogen that came from the moon.
Even if the molecules are "lost" and doomed to escape our orbit, I wonder if this will have any impact on studies that were done on the moon's chemical composition. It seems very apparent that molecules from the earth must be deposited onto the moon if they can reach that far out. In fact, the gravity of the moon should pull them right in if they get close. That would have been continuously "tainting" the surface of the moon with our isotopic signature for billions of years.
Or maybe none of that is possible at all and I have an overactive imagination.
Better known as 318230.
Poses no hazards to astronauts or spacecraft traveling at less than a significant fraction of the speed of light.
A proton can hit with the impact force of a baseball traveling at over one hundred miles per hour.
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But not too far before you hit the firmament. /s
One of my flat earth FB "friends" responded to a FB posted Hubble Deep Field image that it was all embedded in the Firmament.
"This makes the Moon a very high altitude aircraft"
That also makes the Moon the first aircraft. I love science-y slashdot.
But.... we can sush the conspiracy theorists. "Now you know why the Flag was fluttering in the Moon. It was not in vacuum, it was inside out atmosphere.!"
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
The Earth's atmosphere extends all the way to Mars, fact. The "Solar Wind" blows away parts of the upper atmosphere all the time. The magnetosphere reduces that a lot; without it we probably wouldn't have an atmosphere at all. Once they get their measurements fine enough and get a probe around Mars, they will find Earth's atmosphere there too.
Doesn't mean shit.
=^..^= all your rodent are belong to us
This isn't correct. What they're describing isn't an atmosphere at all; it's an exosphere. The difference being that an atmosphere is dominated by particle collisions (and thus behaves like a gas) while an exosphere is dominated by collision-free travel (and thus behaves like individual particles). If at the given temperature, the average particle traveling upwards will experience less than one collision before it reaches the upward end of its arc, it's an exosphere; otherwise, it's an atmosphere.
When was the last time you ran anywhere? I mean with your own legs, not by pressing 'X'?
The Karman Line is drawn at 100 km, not just because that's a nice round number, but because it's roughly the point where an object's momentum and atmospheric friction are roughly equally important.
Above the Karman line objects act more like satellites, with their motion momentum-dominated. Below the Karman line object motion tend to act more like aircraft, with their motion dominated by atmospheric interaction.
Obviously momentum exists below the line and drag exists above the line, which is why satellites in extreme low Earth orbit tend to have their orbits decay. ISS is at about 405 km and decays at roughly 2km/month, requiring regular boosting. The lowest altitude at which an object could make at least one full orbit without boost is about 150 km.
The Karman line is a sensible place to end national sovereignty. Well below that line you need to put energy into an object to cross over a country. Well above the line you need to put energy into an object to avoid crossing over the country. Extending sovereignty above the Karman Line would deny access to space to everyone.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
Everything on Earth is getting fatter.
Table-ized A.I.
The Earth's atmosphere extends as far as it is defined to extend---whatever that is. This seems like someone is just trying to change the definition.
Just because you can detect small concentrations of gas from the atmosphere doesn't make it part of the atmosphere. For example, if I found some New Zealanders in downtown New York, does that mean that New Zealand's territory extends to New York?
Back in the 1960s. There was a popular idea among scientists that Venus and Earth were twin planets, nearly identical at birth. But Earth acquired a giant moon later, which slowly stripped away most of Earth's atmosphere (because the earth's atmosphere extends beyond the Moon's orbit).
Venus never got a giant moon, so it retained all its normal (very heavy) atmosphere, while Earth ended up with its present light and airy air.
You can see this idea in some hard sci-fi written at the time, like Larry Niven's Known Space series.
They detected some particulates, and by that rationale they've extended the boundaries of the atmosphere.
By that same logic, if I get splashed by some mist from a waterfall, does that mean I'm "in the river" or that the river technically extends hundreds of feet from its surface? I don't think reasonable people would agree.
While it's interesting, I'm not sure detecting spatterings of earth's atmospheric molecules "downwind" is a basis for defining the extent of the atmosphere nor even that surprising? I mean, the 'top' of the atmosphere isn't a smooth billiard-ball gaseous surface - it's going to fluctuate wildly with variations in pressure, temperature, wind, weather activity, and this tenuous, highly variable surface is exposed to solar radiation knocking all sorts of gaseous 'spume' free.
-Styopa
Well, if 0.2 atoms/cubic centimetre is an atmosphere then there is no outer space because the density of interstellar space is about 1 particle per cubic centimetre so logically this would imply that the galaxy has an atmosphere.
The atmosphere is so large that it actually manages to fully encompass your mom.
Thanks for the clarification. The alternative - of the moon being subject to friction due to being inside the Earth's atmosphere was concerning me somewhat.
As long as it won't crash into Earth before the sun expands and lights the atmosphere on fire, we're good. At least until the sun expands and lights the atmosphere on fire.
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Not according to the rectal boost regime of one of Dyson's infamous astrochickens.
[*] I decided to split the difference on the two instances of the twin a-acutes.
Today some other Slashdot story had "zebra cosplay" in the story summary. Sheesh. Our collective nerd mojo is a quart down.
Dang... I was all set to call up MegaMaid.
No, one particle per cubic METRE is the density of intergalactic space. The density of interstellar space i.e. the space between the stars in a galaxy, is variable but averages to about 1 million particles per cubic metre which is the same as one particle per cubic centimetre.
It's in orbit, not flying.