The new policykit in Ubuntu 9.10 Karmic doesn’t have a GUI for remembering settings like authentication password to mount a drive/partition. Even without a GUI you can change policies fairly easy by going to /usr/share/polkit-1/actions and editing the right XML file with your favorite editor.

Simply do the following.

Open terminal and enter:
sudo gedit /usr/share/polkit-1/actions/org.freedesktop.devicekit.disks.policy

Find the action id:

Within that action id look for the line:
and replace it with:

Save the file and witness the drives mounted without entering an authentication password.