deposits

So in a recent column I told you all the problems with having water on Mars in recent history -- namely that the atmosphere is too thin to have supported it. But many of you have (rightly) pointed out to me that there is some evidence that there could have been water on Mars a very long time ago, and that would explain some of the major features on Mars. But one problem that remained is this: where are the carbonate deposits at the bottoms of these so called streambeds or dried-up lakes? Well, over the weekend I got an interesting email from National Geographic Magazine about Holden Crater on…