Surprises from Mercury

Earlier today, NASA had a press conference discussing the MESSENGER spacecraft's flyby of Mercury. It hasn't been very long since the data were acquired, and the excitement of the scientists on the panel was tangible. The results are still being interpreted, and some of them are very puzzling.

The most exciting result (in my opinion) was this image:


Nicknamed "The Spider", this crater is about 40 km in diameter and is surrounded by a bunch of radiating troughs. It also happens to be right smack in the middle of the huge 1500 km-in-diameter Caloris basin (which, by the way, is even bigger than scientists previously thought). The mysterious troughs are almost certainly tectonic features related to the ground in the center of the basin bulging and cracking, probably due to the intrusion of molten rock underground.

Everywhere else (that we know of) on Mercury, all we see is compressional tectonics, so this "spider" is really unusual. What caused all the bulging that formed the spider? Nobody know, but I'd bet money that it's related to the Caloris impact.

The recent flyby collected more than 1200 images, plus spectra, and topography data, and this is only the tip of the iceberg. There are two more flybys planned, and then the spacecraft will be in orbit around Mercury, possibly for years. Who knows what other surprises are in store?