The 2017 survey covered a larger area than the 2009 survey. Here, the overall image is the 2017 dataset, but the area within the polygon has been replaced by the 2009 data. If you use the back and forward buttons on your browser to flip between this image and the 2017 mosaic you can see clearly what has been done.

There is also a side-by-side comparison of the 2009 and 2017 data for the area within the polygon.

A few notes on the 2009 data: The 2009 survey was conducted in 2 parts. Only half of it was linked to still images. This portion is in the left half of the polygon on this image. When blending the two portions of the 2009 survey and registering it to the 2017 image some color balancing was done, thus there are also some color balancing differences betwen the two versions of the 2009 mosiac.