A lot of people sent me notes via email and Twitter saying they were out watching the Shuttle and the ISS pass by in the sky last night when Discovery did something very odd and disturbing: there was a flash and then an expanding halo of light around the Shuttle. My first thought when I read this was that it was an orbital maneuver -- a rocket firing -- or maybe a meteor coincidentally near the same spot in the sky, but it turns out to be neither: it was a waste liquid dump, when the astronauts empty waste tanks before landing the Orbiter. SpaceWeather.com has the details, including a very cool picture. I was out last night twice to see Discovery and the ISS, but didn't see the Orbiter either time (I think the predictions I was using were off due to the imminent landing), so I missed the show. Oh well. I imagine more pictures will turn up pretty soon, though, so keep your eyes open. Discovery has a landing opportunity at 19:05 Eastern time (23:05 GMT) today -- they'll make the de-orbit burn at 17:59 if the weather holds up -- and then another opportunity about 90 minutes later at 20:42 (00:42 GMT) if needed. As usual, I'll be tweeting it as it happens.