Color portrait of asteroid 21 Lutetia
Posted by Emily Lakdawalla
21-07-2010 16:28 CDT
Since it doesn't look like the Rosetta mission is going to be releasing any color versions of their Lutetia close-encounter images any time soon, I figured it was time to make one. The data was out there, in the form of two close-approach images that were black-and-white, and one more distant shot in color, but the assembly effort was beyond my skill. Thankfully, Ted Stryk was willing to take a crack at it, and I think he did a great job!
Examining the image, I'm struck by how some craters are so much crisper-looking than others. The crisper-looking ones are probably younger. It does seem odd that the surface isn't totally saturated with smaller craters. In this context, "saturated" means that every time a new crater forms, it obliterates an old one; there's no area of the surface that is devoid of craters. But Lutetia's not like that -- it appears to have some smooth or hummocky plains separating craters. My arm-wavey explanation of this is that seismic shaking from one impact crater may smooth out the terrain, erasing other craters, especially smaller ones. If you look, you'll notice that there do seem to be a pretty good set of very big craters underlying the fresher, smaller ones; seismic shaking wouldn't tend to get rid of those. I think.
When he sent me the image, Ted remarked to me something that I'd been thinking: "That is one funky crater on the terminator. I would probably suspect it was of something other than impact origin if it was on, say, the Moon." I totally agree. It's just not the right symmetrical shape, and it has a weird round lip at its edge, and that dark halo above it. I've got no idea what it is, but it doesn't look like the other craters.