New NASA Grant: I-Xe Dating

Olga Pravdivtseva was awarded a NASA grant to use the iodine-xenon radiometric chronometer to investigate the formation and alteration of components in the CK and CV carbonaceous chondrites. Olga is one of the world’s experts in this technique which provides us with exquisite time resolution to understand processes in the early Solar System. With these measurements, it is possible to constrain the timing of events that happened four billion years ago to +/-100,00 years. This is equivalent to remembering the time at which something that happened a year ago to within 15 minutes!



ALMA images of protoplanetary disks

The Atacama Large Millimeter/submillimeter Array (ALMA) released amazing images of twenty protoplanetary disks in the early stages (first few million years) of planet formation from the Disk Substructures at High Angular Resolution Project (DSHARP).

Our group studies these processes in our own Solar System using rocks that were around then.

Super High-Resolution Meteorite Images

I’ve added a page that will feature some ~billion-pixel images of meteorites I’ve taken with electron and optical microscopes using this or this technique. The first one is a classic: Renazzo, the type sample of the CR chondrites. Renazzo fell in Italy in 1824 with a total mass of 1 kg. Check it out!


The Draconid meteor shower peaks tonight as the Earth sweeps through primordial dust spewed from comet 21P/Giacobini-Zinner. Ernst Zinner was a pioneering researcher in the study of presolar grains, a brilliant scientist and wonderful man who spent most of his career in our lab here at Wash U. Comet 21P is named for Ernst Zinner, but a different Ernst Zinner, a German astronomer, who made the second observation of 21P in 1913. Clearly this is a charmed name for space science!

Large-Field Scanning with an SEM

I posted some new software on github here.

The field-emission scanning electron microscope we use in our lab is a commercial instrument, primarily made for industry to do things like failure analysis of mechanical parts. It is not designed for cosmochemistry, but the best instruments are flexible enough to allow us to do what we need to do efficiently. Our microscope allows for this through a Python-powered scripting interface and easy-to-automate XML files.

In our research we’re frequently looking for rare objects in a relatively large sample — such as hypervelocity impact craters on a metallic surface. So we have a need to acquire electron images over a large surface area that is tilted (or otherwise non-flat) on scales much larger than the depth-of-field of the electron image (typically ten micrometers). Our electron microscope can do autofocus, but this is slow and unreliable. The above code acquires a coarse topographic map and then fits a surface to this map from which it acquires high resolution images. Now we are able to scan centimeter-sized samples to look for micrometer-size features in a reasonable time! The company that makes the microscope certainly can’t foresee all of the uses we have for it, but we have the ability to control the microscope at a very basic level. And since we know how to do math and write code, anything is possible!