[development] Removing modules from Drupal.org

I have two ideas for Drupal modules a couple of years ago and immediately reserved the namespace for them at http://drupal.org/project/ariel and http://drupal.org/project/caliban. I've only just been reminded of these projects, and I now don't have the time to develop the ideas or write the code. How can I got about getting the projects removed from Drupal.org?