Privileged Planet: water here before Earth formed (Introduction)

by David Turell , Thursday, February 17, 2022, 16:20 (1011 days ago) @ David Turell

Another article:

https://www.sciencealert.com/moon-rocks-may-reveal-the-true-source-of-earth-s-water-and...

"...it's commonly accepted that one potential mechanism for water delivery was bombardment from water-bearing asteroids and comets when Earth as we know it today was much younger.

"But a new analysis of rocks collected from the Moon and brought to Earth during the Apollo era suggests that this might not actually be the case.

"Rather, according to a team of researchers at Lawrence Livermore National Laboratory, the likeliest explanation is that Earth formed with its water. In other words, it was here all along.

"'Earth was either born with the water we have, or we were hit by something that was basically pure H2O, with not much else in it," explains cosmochemist Greg Brennecka of LLNL.

***

"...the Moon is a great place to study Earth's history. The Moon formed when two massive objects – one roughly the size of Mars, the other a little smaller than our own world – smacked together and reformed into blobs that would become Earth and its Moon.

***

"To understand the history of the Earth-Moon system prior to the giant impact, the team looked at three lunar samples that crystallized 4.3 to 4.35 billion years ago, examining two isotopes: volatile and radioactive isotope rubidium-87 (87Rb), and the isotope it decays into, strontium-87 (87Sr).

"The latter especially is thought to be a good proxy for understanding the long-term volatile budget of the Moon, and relative abundances of moderately volatile elements, such as rubidium, reflect the behavior of more volatile species, like water.

"Interestingly, the team's analysis revealed that there was very little 87Sr in the Earth-Moon system, even prior to the giant impact. This suggests that both proto-Earth and the impactor, Theia, were strongly depleted in volatile elements, suggesting that volatile depletion was not a result of the giant impact after all.

"This means that the different volatile distributions on Earth and the Moon were inherited from Earth and Theia, which could explain why Earth is wetter. It also suggests that both bodies probably formed in the same general region of the Solar System, rather than Theia forming farther out and migrating in, and that the impact couldn't have happened earlier than 4.45 million years ago.

***

"'There were only a few types of materials that could have combined to make the Earth and Moon, and they were not exotic," explains cosmochemist Lars Borg of LLNL.

"'They were likely both just large bodies that formed in approximately the same area that happened to run into one another a little more than 100 million years after the Solar System formed…but lucky for us, they did just that.'"

Comment: the previous article used a meteorite to propose early water and this article uses the moon, so lots of early water confirmed. The article says 'luck' and I say God.