I recall an explanation of the formation of Jovian moons on the Harvard Smithsonian “CfA Colloquium” YT channel that casually mentioned how various elements freeze out of the solar wind forming ices, and this is the mechanism that allows formation of moons with large amounts of water and elements that are not found in larger quantities within the inner solar system.
I will admit I have a strong bias where I want to believe Theia was an ejected first generation Jovian moon. I don’t like the idea of planets (Theia) forming around Lagrange points as it feels like fitting a theory to the evidence. There is apparently evidence of an earlier generation of Jovian moons and it is the most logical source for such a rogue object traveling slow enough on the solar plane.
With that aside, Earth’s large amount of nitrogen in the atmosphere seems weird. Not that Earth has it as much as why Venus and especially Mars do not. I understand Mars lacks the gravity to hold onto gaseous hydrogen that is stripped away by the solar wind over time, but it can hold onto carbon dioxide. So shouldn’t Mars hold onto nitrogen too?
IMO scientific explanations of Earth’s formation seem to lack the broader perspective of Earth among the solar system as a whole. Earth should look like a Venus:Mars hybrid. Theories seem to start with Earth as a baseline and explain away Venus and Mars as exceptions. It is like we are taking a sample size of 2 and throwing it away in favor of a (much more thorough) sample size of 1, when that sample of 1 has an enormous error source in orbit around it, which most old theories have simply ignored. Like the water isotopes on Earth do not match the comets/asteroids theory, but do match a Jovian source.
So how does Earth acquire a bunch of nitrogen when it is well inside the nitrogen ice line of the solar wind and how does this account for Venus and Mars?
I’m not a scientist, but one could argue that it’s likely that all three planets had nitrogen, but only Earth still has it.
I don’t know much about Venus, but I know that part of why we have way more atmosphere than Mars is due to Earth’s magnetic field. Earth has a much stronger magnetic field than Mars, and it does a pretty good job of shielding us from the solar wind; meanwhile Mars has been slowly trickling atmosphere into the void for ages because it lacks that shielding.
Given that CO2 is actually super heavy, it makes sense that Mars would lose almost everything else first. You mentioned H2, but it’s also almost twice as heavy as N2 - because of this, nitrogen would concentrate at higher altitudes, eventually becoming exposed to the solar wind as lighter gases were stripped away.
As for Venus… Again, I’m not an expert, but a quick search suggests that it has a weak magnetic field as well. With a primarily CO2 atmosphere and a weak magnetic field, one could infer that Venus is in a similar position to Mars, and any significant nitrogen that may have been in its atmosphere has simply been stripped away by the solar wind.
Nope, H2 is ~2g/mol while N2 is ~28g/mol. Nitrogen is a heavier element and nitrogen gas is therefore heavier as well.
I like your hypothesis otherwise!
Sorry, I think my phrasing might have been kind of weird - I was referring to the weights of H2 and N2 relative to CO2, which weighs a whopping 44 grams per mol.
…Although, I just did some quick estimates last night, and “almost twice as heavy” was still pretty far off. CO2 is much closer to 1.5x the weight of N2 than double the weight of N2.
Oh yeah, that makes much more sense, I thought you might’ve meant that. Confusion cleared!