Depending on what exactly you want to accomplish to match the root to a url, I do as follow:
url(r'^$', 'earth.views.Home'),
However, it is sometimes good to have a default page if a request didnt match the url requested (I would use this as the very last rule, otherwise it will catch every request):
url(r'^', 'earth.views.Home'),
As for your origina question, are you sure you have your session middleware activated?