Unable to erase external hard drive with Disk Utility

Macbook Pro (mid 2010) running 10.9

Hello

Recently, my Seagate FreeAgent GoFlex 1 TB external hard drive has not been showing up on my desktop or in finder. The light is on when connected, and in the Disk Utility it appears.

1. It was naturally created with a partition on it (all of the 1TB allocated to it) and it appears in the Disk Utility as well; however, it is grayed out.

2. I clicked the actual drive in DU and it was verified as being ok. I clicked on the partition next to verify and it said "Error disk needs repaired"

3. So I clicked repair, "Disk Utility cannot repair the disk..restore as many as your backed-up files...etc."

4. No problem (the data on the hard drive is used for my Time Machine back ups and my current internal hard drive is working fine with all the data intact)

5. Ok, so I click the erase tab on the entire external hard drive...erase..."Disk cannot be unmounted"

6. Ok, I try to erase the invidual partition..."Could not open disk"

It seems every time I try to erase this drive completely im hitting blocks. I even tried this method from the OS X Recovery menu (Command+R on startup). I would greatly appreciate any help to just get this whole thing external hard drive erased and start anew. How else would I go about this?

(pictures for reference)

Thank you all