"Invalid Index Key" Error - External HFS+ Drive

So I've got this external drive (Seagate Freeagent Go) that I formated with the Journaled filesystem. All of a sudden yesterday I could not access the drive after restarting my computer and when I could no longer see it on my desktop I opened Disk Utility. DU was able to see the drive and the partition but couldn't mount it, and when I ran a Verify/Repair I got the following:

Verify and Repair volume “Artimis”
Checking Journaled HFS Plus volume.
Checking Extents Overflow file.
Checking Catalog file.
Invalid index key
Rebuilding Catalog B-tree.
The volume Artimis could not be repaired.

Error: Filesystem verify or repair failed.


Can anyone help me with a potential fix? I've had no power surges and had just been using the drive with no issues the night before