What happened when the moon 'turned itself inside out' billions of years ago?

[Admin]

The moon underwent a reversal around 4.2 billion years ago, flipping itself "inside out" after a giant impact to create the picture of the faithful lunar companion that we see today.

What happened when the moon 'turned itself inside out' billions of years ago? : Read more

 

[billslugg]

Earth also turned itself inside out very early in its life. There was a lot of iron pieces mixed in with the molten rock. At one point a bunch of them over rode those on the other side of the planet, sank down and formed the iron core. This was a toroidal convection. It also gathered bits of floating crust on one side to form the first continent. That crust, over millions of years, held in the heat underneath it. The far side of the ball of molten rock had no continent, it lost heat to space much faster, got heavy and sank, overcoming the lighter rock under the small continent. The first convection took place 3.5B years ago and the main event transpired in about two weeks. Since then another dozen or so toroidal convections have occurred. Currently, the Atlantic is opening and the Pacific closing. I read all this years ago and can't cite any sources.

 

[Torbjorn Larsson]

It’s possible that Moon took another one for Earth, though their earlier conference contribution [54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806)] has them propose the South Polar Aitken
(SPA) basin-forming impact as the culprit. “The estimated ages of Serenitatis and SPA of ~4.22 Ga [9] and 4.25 Ga [10]
may bracket the overturn event.”

The latest root dating places the split between biology and geology at 4.4 billion years, so life survived a few crust busters – the SPA impactor leaving a 2500 km crater would fit that (~ 100 km impactor). Presumably they never got to the 300-400 km size needed to completely vaporize our ocean.

The first convection took place 3.5B years ago and the main event transpired in about two weeks.

The dating is off by 1 billion years, since Earth had a global ocean (and life) about 4.4 billion years ago. [See e.g. "Extreme environments", Tara A. Mahendrarajah, The Conversation and its refences to the research.] The new dated phylogeny has the first realistic root dating since it pulled it back (by cross bracing) from the usual "as soon as possible" estimate of traditional tree root datings.

 

[billslugg]

Of course, off by a billion. It had to be in the first couple of hundred million years since nearly the entire Earth was molten.