Something that comes up a lot around here, and will in fact come up in the next story, is the problem of planet formation. We understand some of the big picture concepts of what happened, but the details are all a bit mysterious and up for debate. Simple questions like, where did Earth’s atmosphere and ocean water come from, actually lack clear cut answers. Sometimes, the best we can do is look very closely at what we have here, and then compare our world’s elements with the composition of meteorites that we know came from other places in our solar system. 

We think, early in the solar system’s formation, the gas and dust that formed the planets varied with distance from the Sun due to the Sun’s heat and wind changing and moving material around. While nitrogen was scattered throughout the young solar system, the isotopes of nitrogen varied from place to place, and these differences can be measured by looking at nitrogen trapped inside meteorites. In a new study appearing in Nature Astronomy and led by Damanveer Grewal, researchers look at the isotopic signature of nitrogen in a variety of iron meteorites and find indications that our world has nitrogen that originated from both beyond Jupiter and from the inner parts of our solar system.

Nitrogen, and other elements that exist as gases and moderate temperatures, as we have here on Earth, are also called volatiles because of how they expand from ice to gas, as is seen so beautifully in comets.

According to Grewal: Researchers have always thought that the inner part of the solar system, within Jupiter’s orbit, was too hot for nitrogen and other volatile elements to condense as solids, meaning that volatile elements in the inner disk were in the gas phase. Our work completely changes the current narrative. We show that the volatile elements were present in the inner disk dust, probably in the form of refractory organics, from the very beginning. This means that contrary to current understanding, the seeds of the present-day rocky planets — including Earth — were not volatile-free.

This means our world’s nitrogen – or rather some of our world’s nitrogen – has been with us from the beginning. Our world might not have started as a molten rock that had to wait for colliding comets and asteroids to bring it the stuff that makes up our atmosphere and oceans. This is observational data, not a theory or model. Time is still needed to explain how this all happened.

More Information

Rice University press release

“A very early origin of isotopically distinct nitrogen in inner Solar System protoplanets,” Damanveer S. Grewal, Rajdeep Dasgupta and Bernard Marty, 2021 January 21, Nature Astronomy