ubuntu@ubuntu:~$ sudo mount /dev/sda6 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/sda6,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

ubuntu@ubuntu:~$ dmesg | tail
[ 1886.641045] Descriptor sense data with sense descriptors (in hex):
[ 1886.641046]         72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00
[ 1886.641051]         6e 4a 60 08
[ 1886.641053] sd 0:0:0:0: [sda]
[ 1886.641055] Add. Sense: Unrecovered read error - auto reallocate failed
[ 1886.641056] sd 0:0:0:0: [sda] CDB:
[ 1886.641057] Read(10): 28 00 6e 4a 60 08 00 00 08 00
[ 1886.641061] end_request: I/O error, dev sda, sector 1850368008
[ 1886.641076] ata1: EH complete
[ 1886.641105] EXT4-fs (sda6): can't read group descriptor 0