A new look at the family tree

So, now we have this lovely meteorite called Winchcombe (unofficial name for the moment). And everyone has been asking what sort of new and amazing stuff will we learn from it? The answer of course is loads – it’s packed full of exciting information about the earliest days of our Solar System. All we have to do is extract the data. It’s going to be a lot of work, for a lot of people, but also a lot of fun. Everyone is really excited.

One very important topic that Winchcombe might help us to sort out is the carbonaceous chondrite family tree. Yes, sorry, we pretty much know that Winchcombe is a member of an important class of meteorites known as carbonaceous chondrites. Important for lots of reasons. For example, one group, known as the CIs (named after a meteorite called Ivuna), have a composition close to that of the Sun and hence are very much representative of all the material in the Solar System.

Anyway, to get to the point, carbonaceous chondrites are a family made up of about eight main groups (the exact number changes a bit from time to time), and lots of other meteorites that don’t quite fit in, so we call them “ungrouped”. A very recent study led by Zack Torrano of Arizona State University (ASU) has looked into the relationship between two major groups of carbonaceous chondrites, the COs and CMs, and various related, “ungrouped” meteorites. I am not letting the cat out of the bag here by revealing that this is the spectrum of meteorites where Winchcombe will likely slot in.

Zack’s team (I was also a member!) were able to use chromium, titanium and oxygen isotopes to look in detail at how these groups may be related.  It has been known for a long time that COs and CMs show many similarities. The question has always been: are they so similar that they once formed part of a single large asteroid that was destroyed early in solar system history? The new data (and some old data too!) suggests this was probably not the case.

And all those ungrouped samples? Well, they likely came from different asteroids too! The early Solar System was a complicated place, with large numbers of rapidly forming asteroids, most of which would have been quickly destroyed. What arrives on Earth today are just the survivors from a long distant, and chaotic past.

Winchcombe is going to help us enormously in our quest to understand the origins of our Solar System, that’s for sure. The findings of Zach Torrano’s study provides us with important new results and lots of ideas about what was going on in the early Solar System, nearly 4.6 billion years ago. We will be able to put those ideas to the test using data from Winchcombe. And that’s important, because putting ideas to the test in the light of new data is how science works. It’s also fun!

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