BSE image of the OSM 011a eucrite breccia, with clasts outlined where possible. Heavy recrystallisation makes it difficult to find the boundaries between the different rock types.

Backscatter electron (BSE) imaging generates greyscale images based on atomic number contrasts - effectively measuring density. In geological samples, this technique shows the distribution of different minerals which we then combine with other techniques to give the elemental composition.

In the case of this meteorite, BSE imaging helped us identify a number of clasts (pieces of different types of rock that have been mixed together) by showing differences in textures. Meteorite breccias provide records of a wide range of rocks from asteroids and planets, letting us investigate a host of igneous and metamorphic processes that happened billions of years ago.

At the time of classification, we have identified at least three different types of eucrite stuck together in OSM 011a, each with different igneous histories. This meteorite is heavily recrystallised though, suggesting that this rock underwent a period of high temperature metamorphism on it's parent body before being ejected.

Energy dispersive spectroscopy (EDS) provides the abundance of elements at a given point and/or across an area. This means that we can produce high-resolution compositional analysis of samples to work out exactly which minerals we're looking at and where they are.

OSM 011a is largely composed of low-Ca pyroxene, high-Ca pyroxene, and plagioclase. There are a number of accessory minerals including Fe-sulphides, chromite, Fe-metal, ilmenite, and silica - all of which are common in eucrites. Most importantly, the pyroxenes in OSM 011a suggest that this is a distinct meteorite from OSM 011b. Given that they were found on top of each other, this is very exciting!

Some meteorites gain new minerals when they land on Earth and sit outside for a long time before they are found and collected. This meteorite developed patches of baryte (a barium-sulphate) and titanium dioxide around its edges as a result of residing in a hot, dry environment for a significant length of time.

Combined Mg-Ca-Al element map of OSM 011a, overlain with accessory phases.

Red = low-Ca pyroxene; Green = high-Ca pyroxene; Turquoise = plagioclase; Pink = chromite; Purple = silica; White = ilmenite; Yellow = troilite