Intrinsic Water Formation vs. Asteroid Delivery on Early Earth

Key Quotes

"Currently planetary scientists are taught that water wasn't really present when our planet was forming we thought that earth was like pretty bone dry to begin with so it had to be delivered from somewhere else in the solar system."

Michael Wong, an astrobiologist and planetary scientist, explains the prevailing scientific understanding that Earth was initially dry and required external delivery of water. This perspective shaped early hypotheses about the origin of Earth's water.

"And we noticed that comets and asteroids have very different ratios of deuterium to hydrogen or different amounts of hdo mixed in the regular h2o and you can compare that to the amount of hdo that we find here on earth you get a rough sort of estimate for like what the d to h ratio is for the earth you compare that to the d to h ratios for comets oops they don't match at all and then you go to the d to h ratio for these specific kinds of asteroids called carbonaceous chondrites which are these asteroids that are rich in carbon but also very rich in water and you say oh that kind of looks the same."

Wong highlights the significance of the deuterium-to-hydrogen ratio as a key clue in tracing the origin of water. He notes that this ratio in comets does not match Earth's, while certain types of carbonaceous chondrite asteroids show a similar ratio, suggesting a potential source of Earth's water.

"We think that the gas giants may have been actually responsible for this... JUPITER AND SATURN DO MOST OF THE HEAVY LIFTING BUT... SOMETIMES URANUS AND NEPTUNE IN THESE WHAT WE CALL DYNAMICAL SIMULATIONS... AND JUPITER AND SATURN JUST WRECK HAVOC ON THE ENTIRE SOLAR SYSTEM SOMETIMES URANUS AND NEPTUNE ACTUALLY SORT OF FLIP PLACES."

Wong discusses the role of gas giants in planetary science, explaining that their gravitational influence, as shown in dynamical simulations, could have disrupted the solar system. This chaos may have been responsible for flinging water-rich material from the outer solar system inward to Earth.

"The idea that okay you form a terrestrial planet and along with that formation process you create water may have been the original way that people just thought water spawned on a planet because we didn't know that we didn't know about asteroids and comets and so you know this idea that the water had to be delivered from somewhere else only came about once we realized that okay the initial material of the earth was bone dry it was just too hot here for there to be water intrinsically but you could form that water shortly after the planet was created out of bone dry material."

Wong describes an earlier hypothesis where water was thought to form concurrently with a terrestrial planet's creation. This idea emerged before the understanding of asteroids and comets, and before the realization that early Earth's conditions made intrinsic water formation unlikely.

"Basically if you go right to the beginning of planet earth you've got a magma ocean... and the plane is sort of the spacecraft of our imagination is soaring not in an atmosphere of mostly nitrogen and oxygen as we have today but a hot thick atmosphere of hydrogen gas... and the combination of hydrogen gas h2 and this magma ocean which is full of what we call iron oxides basically iron bonded to oxygen those two components iron oxides and hydrogen gas can react together or so the theory went to basically rip the oxygen off of the iron oxide and deposit it in hydrogen therefore creating water."

Wong explains a theoretical mechanism for water formation on early Earth, involving a magma ocean and a thick atmosphere of hydrogen gas. He posits that the reaction between iron oxides in the molten rock and hydrogen gas could have produced water.

"People have come up with this theoretical model of taking iron oxides and hydrogen and oh yeah you should just be able to make water out of that but this paper shows that you actually can in the lab and they used a very clever technique called a diamond anvil cell to do it."

Wong references a recent scientific paper that experimentally validates the theoretical model of water creation. He notes that researchers used a diamond anvil cell, a technique that applies extreme pressure and temperature, to demonstrate this reaction in a laboratory setting.