chmod -v acknowledges but subsequent ls shows no change

/media$ ls -alF
total 24
drwxr-xr-x 4 root root 4096 Jun 12 2013 ./
drwxr-xr-x 26 root root 4096 Apr 4 12:01 ../
drwx------ 1 me me 12288 Apr 2 15:34 OS/
...
/media$ chmod -v o+x OS/
mode of ‘OS/’ changed from 0700 (rwx------) to 0701 (rwx-----x)
/media$ ls -alF
total 24
drwxr-xr-x 4 root root 4096 Jun 12 2013 ./
drwxr-xr-x 26 root root 4096 Apr 4 12:01 ../
drwx------ 1 me me 12288 Apr 2 15:34 OS/

OS is a NTFS file system.

Why can I not set the permissions of OS?

Ubuntu 13.10