THEMIS Image of the Day, April 17, 2019. This VIS image shows part of the floor of Pollack Crater. First imaged by Mariner 9, the high contrast between the crater floor and the bright feature, led to the informal name “white rock” for the bright floor feature. More recent images have shown that the floor of Pollack Crater is darker then normal in that part of the crater, which has produced the high contrast.
THEMIS infrared images of the feature indicate a composition produced by wind deposition, rather than water. Additionally, the deposit does not appear to be solid rock. The deposit is most likely a combination of dust and a more solid material. Taken together, the Mariner 9 image of white rock didn’t hold up under careful study, it’s not white and it’s not rock!
The THEMIS VIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. These false color images may reveal subtle variations of the surface not easily identified in a single band image.