This was a really cool project — measuring New Horizons’ upcoming target by stellar occultation, a sort of eclipse of another star by a distant object in our Solar System where the shadow passed over a small part of Earth. In a few weeks we’ll get to see Ultima Thule up close!
Happy Arrival at Bennu Day!
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!
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!
I took my three-year-old soon to the St. Louis Science Center today to see the Columbia capsule from Apollo 11, two days prior to the 49th anniversary of Apollo 11’s launch. He asked about why it looked all “burned” and he could tell from my extreme enthusiasm how awesome it was.