Tuesday, June 14, 2011
As promised, Dawn's team has released new images of Vesta, the second release of images so far. The first were taken on 3 May, and the ones released today were taken on the first of June. Since then, it has changed from a bright dot into this:
The video shows the same 30 or so minutes of rotation over and over again. Taken almost two weeks ago, the clarity shown here already rivals that of our best images taken from Earth by the Hubble Space Telescope. For comparison this is what the HST showed us a few months ago:
Looking at both of them you can make out the same two dark areas as it spins around with the ridge in between.
The distance right now is about 270,000 km, so already Dawn is almost twice as close as it was when these images were taken and images taken now certainly surpass those taken by the HST. Dawn is still in navigation mode though and images are taken once a week in order to aid this, meaning that we will not be treated to a daily show. I have no problem with waiting a week or two, but I and many others were more than a bit irritated by the month it took between these and the previous ones. Apparently though Dawn's team is well and ready to release many more images, so we won't have to complain again until 2015 if they decide to be stingy with images of Ceres as well. Until then it's all roses and sunshine.
So what is so exciting about Vesta? First of all, it's extremely massive. Put next to a planet it comes out looking like a runt, but its surface area is equal to Ontario or British Columbia, Texas plus Oregon, or a number of other combinations that I've listed here.
Vesta is also massive enough that it has a differentiated interior, which simply means that it was large/massive enough that it was molten when first formed (about 4.6 billion years ago), and eventually the heavier elements sunk to the core while others rose to the top, giving it a crust and core and all the other features that make it more than just a rock and instead a protoplanet.