For people without DXT support, I now have uploaded my 2k,4k,8k Mars textures in JPG format to my Texture Foundry site (cf mars images in site's gallery!).
http://www.celestiaproject.net/~t00fri/texfoundry.php4
Do not forget to deactivate the DXT support button before entering into the download section of the site.
Otherwise, you will not see the new JPG's;-)
Bye Fridger