permission problem - disk on key on PI

[Shlomo Solomon]

Can anyone suggest why I can't seem to change permissions of files on a
disk-on-key mounted on my PI? 
The chmod command reports success, but nothing has changed. 
BTW - all commands over SSH

Here's the Raspbian version: 
pi at raspberrypi /media/D80C-5ACC/pictures $ uname -a
Linux raspberrypi 3.18.7-v7+ #755 SMP PREEMPT Thu Feb 12 17:20:48 GMT
2015 armv7l GNU/Linux

Here's the relevant line from /etc/fstab on the PI:
/dev/sda1      /media/D80C-5ACC vfat    defaults,noatime  0       1


pi at raspberrypi /media/D80C-5ACC/pictures $ ls -la
total 52484
drwxr-xr-x 2 root root    4096 Mar 10 19:51 .
drwxr-xr-x 7 root root    4096 Jan  1  1970 ..
-rwxr-xr-x 1 root root 3387111 Mar  3 08:32 a.jpg
-rwxr-xr-x 1 root root 3470696 Mar  3 08:31 b.jpg
-rwxr-xr-x 1 root root 2924927 Mar  3 08:30 c.jpg

<< snip snip >>

pi at raspberrypi /media/D80C-5ACC/pictures $ sudo chmod -v -R 777 *
mode of `a.jpg' changed from 0755 (rwxr-xr-x) to 0777 (rwxrwxrwx) 
mode of `b.jpg' changed from 0755 (rwxr-xr-x) to 0777 (rwxrwxrwx) 
mode of `c.jpg' changed from 0755 (rwxr-xr-x) to 0777 (rwxrwxrwx) 

<< snip snip >>

pi at raspberrypi /media/D80C-5ACC/pictures $ ls -la 
total 52484
drwxr-xr-x 2 root root    4096 Mar 10 19:51 . 
drwxr-xr-x 7 root root    4096 Jan  1  1970 .. 
-rwxr-xr-x 1 root root 3387111 Mar  3 08:32 a.jpg 
-rwxr-xr-x 1 root root 3470696 Mar  3 08:31 b.jpg 
-rwxr-xr-x 1 root root 2924927 Mar  3 08:30 c.jpg



-- 
Shlomo Solomon
http://the-solomons.net
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