Quick comments on the HiRISE images<br /><br />PIA09552: Typical northern plains with the rough possibly due to volatile sublimation.<br /><br /> <br />PIA09538: Nice example of "thumbprint" terrain, probably a patterned ground phenomena like in the terrestrial arctic. Not sure what you mean by "dark lines" - ay be the two things that look like dust devil trails?<br /><br />PIA09542: Do you mean building footers? If so, why to you think they might be artificial? What indicators are there of artificiality that makes you reject the many natural and likely ways to generate low circular mounds like relief inversion of small craters, ice diapirs, pingos etc?<br /><br />PIA09541: Ditto<br /><br />PIA09537: Bland as only the northern plains can be.<br /><br />PIA09550: The basic texture does look like a cantaloupe! But the dark markings are dust devil streaks. They are present in many, many images of Mars, change over time and we have seen them in the process of being formed. <br /><br />PIA09051: This is a THEMIS image, so much lower resolution. This crater is several km across and the crater walls are slumping. What you are seeing is a slump block. Other have pointed out the flow lines suggesting plastic flow, probably from ice. Did you notice the magnificent gullies?<br /><br />If you are going to look through larger numbers of Mars images I suggest you get a copy of Bill Hartmann's "A traveller's guide to Mars." It is a really excellent guide (pre 2004 missions unfortunately) to what is known and what is not known about Mars. It explains a lot of the common and less common features seen in images and places them in the context of Mars history and in the history of exploration. Bill Hartmann is something of a renaissance man - scientist, writer, artist - and this book is invaluable, easy to read and easy to browse through, with a understated humour and wit.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em> Arthur Clarke</p> </div>