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We May Have Jupiter To Thank For the Nitrogen In Earth's Atmosphere
An anonymous reader writes: Nitrogen makes up about 78% of the Earth's atmosphere. It's also the 4th most abundant element in the human body. But where did all the nitrogen on Earth come from? Scientists aren't sure, but they have a new theory. Back when the solar system was just a protoplanetary disk, the ice orbiting the early Sun included ammonia, which has a nitrogen atom and three hydrogen atoms. But there needed to be a way for the nitrogen to get to the developing Earth. That's where Jupiter comes in. During its theorized Grand Tack, where it plunged into the inner solar system and then retreated outward again, it created shock waves in the dust and ice cloud surrounding the sun. These shock waves caused gentle heating of the ammonia ice, which allowed it to melt and react with chromium-bearing metal to form a mineral called carlsbergite. New research (abstract) suggests this mineral was then present when the Earth's accretion happened, supplying much of the nitrogen we would eventually need for life.
We also have all this damn methane thanks to Uranus.
A bit ironic that without carlsbergite we might not be able to pour Carlsberg from a nitrogen tap.
Nothing ever gets pulled closer, except that something else gets thrown further away in equal measure, anything else would violate conservation of momentum. This page give a bit of an overview: http://www.boulder.swri.edu/~k...
As I understand it the idea is that they were acting within a relatively dense gas-and-asteroid cloud rather than the modern vacuum. Jupiter was moving inwards as it scooped up gas and asteroids from the inner system, launching most of that material into the outer system. And miniscule Saturn was towed along in it's wake. Eventually the orbital resonance with an encroaching Saturn slowed and reversed Jupiter's motion, at which point they began scooping up the detritus that had been thrown outward on their inward journey and hurling it back inward again while they moved outwards, eventually moving outwards far enough that they could start scooping up the previously undisturbed outer-system cloud and hurling it inward, moving them even farther out than they had originated. And of course Uranus and Neptune had meanwhile been busy throwing more material inwards from the far-outer system as they performed their own migrations, further fueling the outward migration of Jupiter.
Think of it like a gravitationally powered rocket engine - every asteroid that does a gravitational slingshot around Jupiter transfers just as much momentum to Jupiter as it does to the asteroid.
Eventually Jupiter's orbit stabilized when it ran out of enough outer-system detritus to propel it further outward, while orbital resonance continued to propel Saturn even further outward at the expense of propelling Jupiter slightly inward, solidifying the new orbital position.
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Yes, but "in the universe" is a much different location than "in the narrow ribbon of proto-planetary material that formed the Earth". Hydrogen and Helium are by far the most common elements by mass, and yet there's very little of either on Earth, due in large part to the fact that they are too light to be gravitationally bound by such a small planet unless incorporated into other compounds.
Consider that a proto-planetary disc around a star would act as something of a centrifuge, causing stratification by molecular weight, so elements would tend to clump together according to the molecular weights of the compounds they were most stably bound into at that point in time. And anything that changed the stability of those molecules - say heating, or a change in concentration of reactive chemicals due to large bodies causing mixing between cloud strata - would change the preferred strata of said elements as they were incorporated into molecules with a different mass, as well as the mixing itself causing molecules to deposit on proto-planetary bodies outside their preferred strata.
--- Most topics have many sides worth arguing, allow me to take one opposite you.