Theory suggests blobs of material in Earth's mantle are remnants of protoplanet | Hacker News Reader

Theory suggests blobs of material in Earth's mantle are remnants of protoplanet

phys.org

26 pointsHooke13 comments

"Dude, everyone knows it is Krypton." -- anonymous.

I read this paper and found it pretty neat. That said I wouldn't have wanted to be around at the time :-).

I have always wondered if whacking a planet hard enough would allow a large proportion of its heavier elements to congregate at the core. And if such an event was a requirement for life to arise as the magnetosphere provided by the Earth's core shields relatively delicate biology from the full blast of the solar wind.

Also heavy elements that are required in enzymatic processes. I developed a theory about this many years ago after living on a volcanic island, and then told it to an astrophysicist at NASA, who said I should use it as my application essay to Stanford, which must have at least been entertaining enough for them to give me a chance. I don’t think it was a normal planet though. The high density and existence of gold here suggests a chunk of supernova emission. This planet may be exceptionally rare, and I worry about life ending because there aren’t a lot of these flying around anymore.

It's very weird for someone like me that does not work in geology [1], but apparently it is quite well documented https://en.wikipedia.org/wiki/Large_low-shear-velocity_provi... It has an animation that is very nice to understand the location and size.

[1] Relevant xkcd: https://xkcd.com/2058/

The interesting part of the great strike hypothesis is the question if such even is required for an earth like planet to be tricky earth like - lots of liquid water and an active core capable of sustaining a magnetic field over billions of years.

If this would be the only way that true earth like planets actually form this might make earth even rarer and could mean that most earth size planets within the habitable zone of their host star that aren’t relatively young could be just barren wastelands incapable of supporting life as we know it.

I was a little disappointed that the article talks about impact models but doesn't have any pictures or videos visualizing impact simulations. A quick YouTube search came up with this:

https://www.youtube.com/watch?v=MxgwJ0GZlBo

Interesting.

A numerical model like this is cool, but personally I think it can never be proved. How to prove or dis-prove geological theories about the detailed earth evolution on the scale of millions to billions of years is a big challenge.

Testing the parts that supposedly came from the planet and comparing them to the moon would provide a lot of evidence for or against this theory. It can never be proven, but that's not the end goal anyway.

A while ago I asked a friend who is a geologist working for a Platinum mine how come Platinum only shows up in certain places. His answer was basically along these lines.

Our planet ate its sibling in the stellar womb.

I still think it's fascinating that the moon doesn't have any effective rotation.

I mean NONE .. what are the odds of that?

Additionally, the fact that it's the PERFECT distance from the earth to the moon to perfectly obscure/eclipse the sun?

WTF moon!? How'd you get so awesome!?

I think the rotation thing is explained by tidal locking.

It takes power to rotate in a gravitational field, because there are tides that pull both Earth & Moon into little ovoids and cause friction. After a long enough time any pair of orbiting bodies will become tidally locked. This is especially true when objects are relatively close compared to their diameter (moon is only 30 earths away), and the smaller object will lock much sooner, because it has much less angular momentum.

The moon used to be larger because it was closer, it every so slightly moves away from the earth. On a geological scale it will quite soon move far away that a total eclipse of the sun will no longer be possible.

It’s awesome now but in a few 100’s million of years it won’t be.

On a cosmological scale we’ll be eaten by our swelling sun in a blink of an eye too so there’s that...

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