Meanwhile in Manchester…

13 Jan 2020

Readers will have seen and read about a lot of goings on “down south” in Rothera and at the Outer Recovery ice fields, and the results of the team’s searches at the field site near the Shackleton Mountains. This is only part of the story (though a key one)!

Back in Manchester the rest of the Lost Meteorites of Antarctica team have been busy, so we thought it only right that we give a brief overview of the work going on behind the scenes. Recently mentioned, Liam and John provided support to Wouter with the technical glitches and have of course been instrumental throughout the project from its initial design, build, lab testing and field testing.

Patches of blue ice at the base of cliffs in the Theron Mountains. Selecting the right spot is key to finding meteorites. [Credit: Romain Tartese]

In parallel with the detector system build, Andy has been working with lots of data analysis (using satellite datasets and climate model outputs) to figure out whereabouts the team was best searching for meteorites. Antarctica is a big place and meteorites are only found in a few spots. Sometimes people head out there to come back empty handed, so we wanted to do our best for last season to make sure we found a “blue ice area” that harboured meteorites. First of all, a selection of candidate sites were tracked down by Katie (before the current project was funded) and then reduced to a long-list of those accessible on a logistics basis with the help of BAS. Then, using a combination of estimates of snowfall (that tells us something about the rate at which meteorites accumulate in a given area), and the local surface ice flow and wind scouring (that tells about the rate of loss of meteorites), we came up with a prediction of what density of meteorites we expected across these candidate sites. That prediction enabled us to refine and rank our preferred areas for Katie to visit last year. Thankfully she and Julie Baum confirmed our estimates and found some meteorites! Once we had decided on particular areas, Andy was involved in making custom maps for the team’s GPSs from hi-res satellite imagery, more detailed estimates of which individual ice fields to return to (from the data and samples Katie collected last year), and the logistics involved in shipping and planning. At the moment he’s the main contact back in Manchester and has been responsible for posting updates sent through by satellite phone while Geoff, Katie, Wouter and Romain have been at the remote field site.

There’s lots of posts about trying to find meteorites on the blog, but once we find them — what happens to them? That job is being undertaken by Jane and Tom working with members of the isotope group.

Well, we’ve made sure the potential meteorites have all been collected following defined procedures to keep them as free from any contamination as possible, for example, they only come into contact with stainless steel equipment used to get them into polythene bags, and every sample is double-bagged. They are even kept at sub-zero temperatures throughout their journey back to the UK, giving us the best chance of keeping them in pristine condition for future science. Jane, working with Katie, Rhian Jones and with folks at the meteorite group at the NHM, has been working out the necessary steps for the preliminary examination plan for classifying the meteorites, to ensure the samples do not get contaminated, and that every stage of examination is thoroughly documented. In line with this, the first ten samples from last season have now been thawed and she is using “CT-scanning” to look inside the rock and get an initial idea of what it is made of, before deciding how to break or cut the sample. Small pieces will then be mounted on glass slides in order to examine them with microscopes so that they can be formally classified into their different classes.

The “light box” set up used to acquire the images for 3D photogrammetry scans. [Credit: Tom Harvey]

Now the first samples from last year’s reconnaissance trip have been defrosted, Tom has been working to scan the fresh sample exteriors with a technique called photogrammetry. Photogrammetry uses information in pictures of a sample (in this case a meteorite) which show overlapping surface features to position that bit of the sample in 3D space — meaning that we can generate an electronic 3D model of the sample! These models are really useful because they preserve a record of the sample exterior prior to analysis (or, if needs be, cutting), and mean that we can zoom in on parts of the surface that are particularly interesting, which is great for curation and initial characterisation purposes and gives a permanent record of what the meteorite looked like when it was found.

And as this post goes online, it sounds like this year’s samples might just be starting to make the long journey back to the UK… holding the promise of lots more interesting science.