So how long has it been since they landed? Also why have they only traveled 3 miles. That seems pretty slow but If they are gathering every bit of Information that could be a reasonable speed. I'll look into the article and tell you what I think.

He said they only travelled 7 miles, and that is because they are very slow in order to avoid running into an object hard enough to be damaged. Furthermore, they have pretty much been going over the same area again and again, not travelling outward very much, and they do shut down every night to rest.