Now THAT is air…
But what is THAT?
And how did it GET HERE?
WHAT'S WITH THE AIR?
Hey nose and/or mouth-breathers, Trace here for DNews.
There's a question going around Reddit Science right now that caught my eye: Where did Earth's
atmosphere come from?
And we started talking about it, and we weren't sure either…
"atmosphere" literally means, "sphere of air," but "air" isn't really right either -- because
that's just what we have on earth.
Venus and Titan have atmospheres, in that gases permanently cover their surface; in
fact, a number of the bodies in our solar system have atmospheres -- even the Sun.
The gases surrounding the celestial bodies are held, suspended in space by the gravity
of their host planets, which determines a lot about their makeup and potential to support
human life.
Our atmosphere came into being not long after the Earth cooled 4.6 billion years ago.
As hydrogen and helium are extremely prevalent in the universe chances are our atmosphere
contained them too, early on.
The sun is 98 percent helium and hydrogen...
However, as we were so close to the sun and pretty hot ourselves, much of those lighter,
faster-moving elements escaped Earth's gravity.
Jupiter, Saturn and Uranus got to keep theirs because they were so far away, and so much
more massive.
Scientists believe as radioactive elements decayed and the Earth cooled, our remaining
elements coalesced into solids, liquids and gases.
A 2009 paper published in the journal Science says, at this point, the Earth was hit by
many, many comets and meteors -- bringing water vapor, krypton, xenon and other atmospheric
materials.
Another, older, theory states it was volcanoes that spewed water vapor into the sky.
We'll leave it up to the researchers, but needless to say, at this point we know there
was water vapor, carbon dioxide, ammonia, methane, and neon that they think was already
swirling over our hot crust.
And yet ANOTHER theory proposes that 4.5 billion years ago, when the proto-earth was getting
hit by asteroids including a GIANT one that formed the moon, the neon in our atmosphere
was BLOWN OFF and a beneficial ratio of gasses were left behind.
From there, a secondary atmosphere began to form from those volcanic blasts and the leftover
heat inside the planet.
Heavier elements like nitrogen split out forming 78% of our atmosphere today as well as the
carbon dioxide and water…
As the planet cooled … life began to form and they did the rest.
2.7 billion years ago, when the first primitive life forms began to form, they lived anaerobically,
or without air.
These extremophiles digested sulfates for energy!
Completely ignoring the atmosphere.
Later, cyanobacteria or blue-green algae evolved to suck in carbon dioxide and output oxygen
using photosynthesis.
These guys are still around today.
They use the energy from the sun, and carbon dioxide to produce oxygen.
Eventually, and scientists know it happened, but are unclear HOW, there was so much oxygen
in our air, that it poisoned organisms that couldn't process it, causing a mass extinction.
Microorganisms that COULD burn O2 survived as did the cyanobacteria and over millions
of years, they added enough O2 to support the evolution of oxygen-sucking animals, which
evolved into the living animals today like you and me.
As the planet continued to cool, the water vapor began to rain down, dissolving the CO2
gases into it.
The oceans were formed in this way, and the cyanobacteria spread creating more oxygen.
Oxygen is hard to find on most planets because it tends to react with everything.
It rusts metals, it burns easily, it can make water.
So how it got to the balance of 21-percent that we have today is still being studied.
By final count, according to HowStuffWorks.com, our air is "78 percent nitrogen, 21 percent
oxygen, 0.9 percent argon and 0.03 percent carbon dioxide.
The remaining 0.07 percent consists of water vapor, hydrogen, ozone, neon, helium, krypton
and xenon."
*breathes* and it's pretty nice.
Do you have other science questions?
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SpaceOut!
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July 30th at 4pm Pacific Time.
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