AmazonS3 is having issues right now which is affecting the display/download/upload of some content on the site (notably file downloads, uploads, the mosaic and some other images), apologies for the inconvenience!
Seeing as this is affecting a large portion of the internet, it should be back soon - we'll keep you updated on the status if there are any changes.
Update 1:00pm PST - Service seems to be slowly resuming - expect slow downs as the entire internet tries to access their data at the same time