Starship Asterisk*

Chris Peterson wrote: ↑Fri Dec 08, 2023 10:40 pm

johnnydeep wrote: ↑Fri Dec 08, 2023 7:11 pm

alter-ego wrote: ↑Fri Dec 08, 2023 5:56 pm
Sky & Tel: Bits of Theia Might Be in Earth's Mantle
LInked Nature article: Moon-forming impactor as a source of Earth’s basal mantle anomalies

Interesting. The statement that the cores of proto-Earth and Theia likely merged would seem to rule out a "glancing blow". It's also not clear to me how much of Theia ended up in the moon. The graphic in the article shows the Moon as a color that appears to be a mix of the colors of the two mantles, but yet different from the color of the mantle of the post-impact Earth:

This diagram outlines the evolution of Earth's mantle. Theia hits Earth, the cores merge, and the Moon as a result of the impact. However, Theia's mantle is denser than Earth's so it doesn't mix in; instead it sinks over time, glomming together on either side of the core. - Qian Yuan / ASU

---

https://skyandtelescope.org/astronomy-news/bits-of-theia-might-be-in-earths-mantle/#:~:text=The%20simulations%20suggest wrote:
The simulations suggest that Theia might have been much larger than previously suspected, perhaps four times as massive as Mars, and denser too. The Apollo samples support the high density. Lunar rocks exhibit a relatively low ratio of heavy hydrogen (deuterium) to light hydrogen, from which the team calculates that Theia's mantle must have been between 2% and 3.5% denser than Earth in order to retain the light gas. This estimate is consistent with the high density required by their simulations.

There are several very plausible simulations that start with very different situations and end up with what we currently observe. I don't think we're going to really be able to narrow things down until we have a lot more lunar samples.

johnnydeep wrote: ↑Fri Dec 08, 2023 7:11 pm

alter-ego wrote: ↑Fri Dec 08, 2023 5:56 pm

johnnydeep wrote: ↑Fri Dec 08, 2023 3:29 pm

Ok. I guess "the jury is still out" as the saying goes.

Sky & Tel: Bits of Theia Might Be in Earth's Mantle
LInked Nature article: Moon-forming impactor as a source of Earth’s basal mantle anomalies

Interesting. The statement that the cores of proto-Earth and Theia likely merged would seem to rule out a "glancing blow". It's also not clear to me how much of Theia ended up in the moon. The graphic in the article shows the Moon as a color that appears to be a mix of the colors of the two mantles, but yet different from the color of the mantle of the post-impact Earth:

This diagram outlines the evolution of Earth's mantle. Theia hits Earth, the cores merge, and the Moon as a result of the impact. However, Theia's mantle is denser than Earth's so it doesn't mix in; instead it sinks over time, glomming together on either side of the core. - Qian Yuan / ASU

---

https://skyandtelescope.org/astronomy-news/bits-of-theia-might-be-in-earths-mantle/#:~:text=The%20simulations%20suggest wrote:
The simulations suggest that Theia might have been much larger than previously suspected, perhaps four times as massive as Mars, and denser too. The Apollo samples support the high density. Lunar rocks exhibit a relatively low ratio of heavy hydrogen (deuterium) to light hydrogen, from which the team calculates that Theia's mantle must have been between 2% and 3.5% denser than Earth in order to retain the light gas. This estimate is consistent with the high density required by their simulations.

alter-ego wrote: ↑Fri Dec 08, 2023 5:56 pm

johnnydeep wrote: ↑Fri Dec 08, 2023 3:29 pm

Chris Peterson wrote: ↑Fri Dec 08, 2023 3:09 pm
The simulations I've seen involve glancing blows where most of the colliding body (now melted) continues on its way. But there are lots of possible scenarios.

Ok. I guess "the jury is still out" as the saying goes.

Sky & Tel: Bits of Theia Might Be in Earth's Mantle
LInked Nature article: Moon-forming impactor as a source of Earth’s basal mantle anomalies

https://skyandtelescope.org/astronomy-news/bits-of-theia-might-be-in-earths-mantle/#:~:text=The%20simulations%20suggest wrote:
The simulations suggest that Theia might have been much larger than previously suspected, perhaps four times as massive as Mars, and denser too. The Apollo samples support the high density. Lunar rocks exhibit a relatively low ratio of heavy hydrogen (deuterium) to light hydrogen, from which the team calculates that Theia's mantle must have been between 2% and 3.5% denser than Earth in order to retain the light gas. This estimate is consistent with the high density required by their simulations.

johnnydeep wrote: ↑Fri Dec 08, 2023 3:29 pm

Chris Peterson wrote: ↑Fri Dec 08, 2023 3:09 pm

johnnydeep wrote: ↑Fri Dec 08, 2023 3:01 pm

So then what did happen to the stuff that made up Theia? Was it just ejected away from the Earth-Moon system? It would seem very unlikely that none of Theia was incorporated.

The simulations I've seen involve glancing blows where most of the colliding body (now melted) continues on its way. But there are lots of possible scenarios.

Ok. I guess "the jury is still out" as the saying goes.

Chris Peterson wrote: ↑Fri Dec 08, 2023 3:09 pm

johnnydeep wrote: ↑Fri Dec 08, 2023 3:01 pm

Chris Peterson wrote: ↑Fri Dec 08, 2023 2:53 pm
Yeah, I think the strong evidence that the Earth and Moon are made of nearly identical material must mean either that Theia wasn't incorporated, or was equally incorporated in both bodies. And simulations and other physical measurements argue against the latter.

So then what did happen to the stuff that made up Theia? Was it just ejected away from the Earth-Moon system? It would seem very unlikely that none of Theia was incorporated.

The simulations I've seen involve glancing blows where most of the colliding body (now melted) continues on its way. But there are lots of possible scenarios.

johnnydeep wrote: ↑Fri Dec 08, 2023 3:01 pm

Chris Peterson wrote: ↑Fri Dec 08, 2023 2:53 pm

johnnydeep wrote: ↑Fri Dec 08, 2023 2:47 pm

And I think it's still debated how much of the Moon's material is from the presumed impactor ("Theia") and how much is from the proto-Earth. Although this paragraph from Wikipedia seems to imply that none of Theia remained to become part of the moon? :

Yeah, I think the strong evidence that the Earth and Moon are made of nearly identical material must mean either that Theia wasn't incorporated, or was equally incorporated in both bodies. And simulations and other physical measurements argue against the latter.

So then what did happen to the stuff that made up Theia? Was it just ejected away from the Earth-Moon system? It would seem very unlikely that none of Theia was incorporated.

Chris Peterson wrote: ↑Fri Dec 08, 2023 2:53 pm

johnnydeep wrote: ↑Fri Dec 08, 2023 2:47 pm

Chris Peterson wrote: ↑Fri Dec 08, 2023 2:29 pm

That collision left no original material larger than dust grains. The entire surface of the Moon is reformed.

And I think it's still debated how much of the Moon's material is from the presumed impactor ("Theia") and how much is from the proto-Earth. Although this paragraph from Wikipedia seems to imply that none of Theia remained to become part of the moon? :

https://en.wikipedia.org/wiki/Origin_of_the_Moon#:~:text=The%20standard%20giant%2Dimpact%20hypothesis wrote:
The standard giant-impact hypothesis suggests that a Mars-sized body, called Theia, impacted the proto-Earth, creating a large debris ring around Earth, which then accreted to form the Moon. This collision also resulted in the 23.5° tilted axis of the Earth, thus causing the seasons.[1][irrelevant citation] The Moon's oxygen isotopic ratios seem to be essentially identical to Earth's.[4] Oxygen isotopic ratios, which may be measured very precisely, yield a unique and distinct signature for each Solar System body.[5] If Theia had been a separate protoplanet, it probably would have had a different oxygen isotopic signature than proto-Earth, as would the ejected mixed material.[6] Also, the Moon's titanium isotope ratio (50Ti/47Ti) appears so close to the Earth's (within 4 parts per million) that little if any of the colliding body's mass could likely have been part of the Moon.[7]

Yeah, I think the strong evidence that the Earth and Moon are made of nearly identical material must mean either that Theia wasn't incorporated, or was equally incorporated in both bodies. And simulations and other physical measurements argue against the latter.

johnnydeep wrote: ↑Fri Dec 08, 2023 2:47 pm

Chris Peterson wrote: ↑Fri Dec 08, 2023 2:29 pm

FLPhotoCatcher wrote: ↑Fri Dec 08, 2023 7:50 am I know this comment is a little late, but... Could the unusual mountains opposite the orbiter near the lunar terminator be remnants of the original body that slammed into the earth, or even part of Earth's crust? Or did the original moon have to have been totally liquid rock?

That collision left no original material larger than dust grains. The entire surface of the Moon is reformed.

And I think it's still debated how much of the Moon's material is from the presumed impactor ("Theia") and how much is from the proto-Earth. Although this paragraph from Wikipedia seems to imply that none of Theia remained to become part of the moon? :

https://en.wikipedia.org/wiki/Origin_of_the_Moon#:~:text=The%20standard%20giant%2Dimpact%20hypothesis wrote:
The standard giant-impact hypothesis suggests that a Mars-sized body, called Theia, impacted the proto-Earth, creating a large debris ring around Earth, which then accreted to form the Moon. This collision also resulted in the 23.5° tilted axis of the Earth, thus causing the seasons.[1][irrelevant citation] The Moon's oxygen isotopic ratios seem to be essentially identical to Earth's.[4] Oxygen isotopic ratios, which may be measured very precisely, yield a unique and distinct signature for each Solar System body.[5] If Theia had been a separate protoplanet, it probably would have had a different oxygen isotopic signature than proto-Earth, as would the ejected mixed material.[6] Also, the Moon's titanium isotope ratio (50Ti/47Ti) appears so close to the Earth's (within 4 parts per million) that little if any of the colliding body's mass could likely have been part of the Moon.[7]

Chris Peterson wrote: ↑Fri Dec 08, 2023 2:29 pm

FLPhotoCatcher wrote: ↑Fri Dec 08, 2023 7:50 am I know this comment is a little late, but... Could the unusual mountains opposite the orbiter near the lunar terminator be remnants of the original body that slammed into the earth, or even part of Earth's crust? Or did the original moon have to have been totally liquid rock?

That collision left no original material larger than dust grains. The entire surface of the Moon is reformed.

https://en.wikipedia.org/wiki/Origin_of_the_Moon#:~:text=The%20standard%20giant%2Dimpact%20hypothesis wrote:
The standard giant-impact hypothesis suggests that a Mars-sized body, called Theia, impacted the proto-Earth, creating a large debris ring around Earth, which then accreted to form the Moon. This collision also resulted in the 23.5° tilted axis of the Earth, thus causing the seasons.[1][irrelevant citation] The Moon's oxygen isotopic ratios seem to be essentially identical to Earth's.[4] Oxygen isotopic ratios, which may be measured very precisely, yield a unique and distinct signature for each Solar System body.[5] If Theia had been a separate protoplanet, it probably would have had a different oxygen isotopic signature than proto-Earth, as would the ejected mixed material.[6] Also, the Moon's titanium isotope ratio (50Ti/47Ti) appears so close to the Earth's (within 4 parts per million) that little if any of the colliding body's mass could likely have been part of the Moon.[7]

FLPhotoCatcher wrote: ↑Fri Dec 08, 2023 7:50 am I know this comment is a little late, but... Could the unusual mountains opposite the orbiter near the lunar terminator be remnants of the original body that slammed into the earth, or even part of Earth's crust? Or did the original moon have to have been totally liquid rock?

Chris Peterson wrote: ↑Fri Dec 08, 2023 2:56 am

Avalon wrote: ↑Fri Dec 08, 2023 2:52 am Is there any way to gauge how long ago the Kepler crater was formed? Even a wild guess?

There are estimates based on layering and overlying crater counts. Somewhere between 100 and 800 million years?

Avalon wrote: ↑Fri Dec 08, 2023 2:52 am Is there any way to gauge how long ago the Kepler crater was formed? Even a wild guess?

Rauf wrote: ↑Thu Dec 07, 2023 9:04 pm

johnnydeep wrote: ↑Thu Dec 07, 2023 8:08 pm

Rauf wrote: ↑Thu Dec 07, 2023 1:35 pm

I think you're mistaking crater rays for smoke?

Neither smoke nor rays. I think Mulk was noticing the cable loops connecting the two solar panels:


cable loops on orion solar panels.jpg

That doesn't look like smoke though!

johnnydeep wrote: ↑Thu Dec 07, 2023 8:08 pm

Rauf wrote: ↑Thu Dec 07, 2023 1:35 pm

Mulk wrote: ↑Thu Dec 07, 2023 7:32 am What is the "smoke" coming off the solar array? Damage?

I think you're mistaking crater rays for smoke?

Neither smoke nor rays. I think Mulk was noticing the cable loops connecting the two solar panels:


cable loops on orion solar panels.jpg

Rauf wrote: ↑Thu Dec 07, 2023 1:35 pm

Mulk wrote: ↑Thu Dec 07, 2023 7:32 am What is the "smoke" coming off the solar array? Damage?

I think you're mistaking crater rays for smoke?

Mulk wrote: ↑Thu Dec 07, 2023 7:32 am What is the "smoke" coming off the solar array? Damage?