Can a scan or X-ray tell if a rock is a meteorite?
Some scans help. X-ray fluorescence can detect nickel, and CT scans show metal grains inside, but full confirmation needs lab analysis of a sample.
Laboratories use several non-destructive methods to examine suspected meteorites. Each gives useful clues, though usually not complete proof on its own.
X-ray fluorescence (XRF). A handheld or benchtop XRF analyser fires X-rays at a surface and measures the X-rays given off by different elements. It can detect nickel, which is present in most meteoritic metal but rare in Earth's iron and iron ores. A metallic sample with significant nickel, typically more than about 5 per cent, is a promising sign. XRF only analyses the surface, so rust or dirt can affect results.
CT scanning. X-ray computed tomography creates three-dimensional images of the inside of a rock. It shows dense metal grains, chondrules and cracks, helping to identify chondrites without cutting them. It is used by researchers to study rare meteorites.
Magnetic susceptibility. Meters measure how strongly a rock responds to a magnetic field. Meteorite types have characteristic ranges, which helps distinguish meteorites from most Earth rocks.
Density measurement. Accurate density measurement narrows down possibilities.
Final confirmation. Official classification requires a polished thin section examined under a microscope and chemical analysis of minerals with an electron microprobe, plus, for many types, oxygen isotope measurements. This involves removing a small sample.
Most identification services first look at photographs and simple test results before deciding whether further analysis is worthwhile. Some museums and universities offer free initial assessments.