4.5 billion year old space rock tells us new things about Solar System

October 30, 2023 11:48 PM

Sahara space rock 4.5 billion years old upends assumptions about the early Solar System
posted by chariot pulled by cassowaries (12 comments total)

It is amazing that we can figure out the ages of these rocks, all the products of exploding stars. It is amazing that we are here and made of exploding star stuff, figuring these things out along the way.
posted by They sucked his brains out! at 12:13 AM on October 31, 2023 [11 favorites]

Interesting, thank you.

Some long ago place had a volcano, created this rock, got blowed up, and then this thing crashed into Earth. What a story!
posted by Meatbomb at 1:44 AM on October 31, 2023

Aluminium-26 is very useful stuff for scientists who want to understand how the Solar System formed and developed. Because it decays over time, we can use it to date events – particularly within the first four or five million years of the Solar System’s life.

The decay of aluminium-26 is also important for another reason: we think it was the main source of heat in the early Solar System. This decay influenced the melting of the small, primitive rocks that later clumped together to form the planets.

Aluminum-26 as the main source of the heat that formed the small bodies of the early Solar System!

I read a long time ago that about half the heat of the Earth's interior came from radioactive decay, but this role tor Al-26 is still surprising.
posted by jamjam at 2:09 AM on October 31, 2023 [4 favorites]

4.5 billion year old space rock

Wait - - this isn't a review of the new Rolling Stones album?
posted by fairmettle at 3:08 AM on October 31, 2023 [10 favorites]

Can someone explain what "assumptions about the early solar system" were upended? I did not get that from reading either the linked article or nature article it linked. Just that it differed from some proposed ideas.
posted by sabraonthehill at 6:15 AM on October 31, 2023 [1 favorite]

It's wild that rocks have a state that is considered primitive. Looking at exposed rock along the highways in Pennsylvania, you know that geology can be wild (something made, moved, and then bent this huge layer of rock and it looks like that in degrees for miles below me). Somehow, this is equally mind blowing that there was an egg before this chicken and we can sorta know why and how.
posted by Slackermagee at 6:18 AM on October 31, 2023 [6 favorites]

It would have been a bigger headline had the 4.5 billion year old space rock plead the fifth.
posted by RonButNotStupid at 6:47 AM on October 31, 2023 [1 favorite]

> Can someone explain what "assumptions about the early solar system" were upended?

I think the headline writer was just making shit up. Maybe the title was generated by a LLM.

This bit is the only plausible candidate, being the only original insight claimed at TFA:

The comparison with a group of achondrites called volcanic angrites was particularly interesting. We found that the parent body of Erg Chech 002 must have formed from material containing three or four times as much aluminium-26 as the source of the angrites’ parent body.
This shows aluminium-26 was indeed distributed quite unevenly throughout the cloud of dust and gas which formed the solar system.

The fact that the rock they were looking at had fractions of Pb and U isotopes that allowed them to date it with great precision, allow them to claim that the Al-26 distribution in the early solar system was non-uniform. Was there an assumption that the early solar system was homogeneous with respect to its Al-26 fraction? IDK, seems doubtful.
posted by Aardvark Cheeselog at 8:36 AM on October 31, 2023 [3 favorites]

However, to use aluminium-26 to understand the past, we need to know whether it was spread around evenly or clumped together more densely in some places than in others.
posted by Greg_Ace at 9:30 AM on October 31, 2023 [1 favorite]

Was there an assumption that the early solar system was homogeneous with respect to its Al-26 fraction? IDK, seems doubtful.

Yes, the heterogeneity of the presolar nebula was known, mainly from isotopic variations in presolar grains in carbonaceous chondrites. Those are dark-colored meteorites that came from asteroids that never melted, so they're just agglomerations of bits that stuck together, so they preserve a lot of information about the presolar nebula.

This is an interesting bit of evidence from an achondrite. It tells a neat story about high concentrations of Al-26 leading to melting of bodies very early in the Solar System's history. Unlike carbonaceous chondrites, achondrites have been melted and mixed up and altered, so they aren't quite where you'd expect to find a lot of information about the very young Solar System.

But it's hard to convey that in a headline.
posted by BrashTech at 4:46 PM on October 31, 2023 [8 favorites]

Very cool! I tried to figure out what the gravity would feel like on (4) Vesta, but couldn't find a source.
posted by objectfox at 8:54 AM on November 1, 2023

I tried to figure out what the gravity would feel like on (4) Vesta, but couldn't find a source.

Peter Thomas at Cornell has definitely done this calculation based on Hubble observation, but I don't think it's published. The answers are very weird because 1) Vesta is not a sphere, and 2) Vesta is spinning pretty fast.

There's better data from the Dawn mission, of course. I think this paper probably describes the up-to-date shape and gravity model, though it's paywalled.
posted by BrashTech at 12:54 PM on November 2, 2023