ASM - v$asm_disk not showing group# shown by v$asm_diskgroup

Hi, we have a 10g R2 database with RAC and ASM

Looking at the following queries, can someone please shed some light as to why v$asm_disk is showing only group_number 2 and 3 and not 1?
As evident from v$asm_diskgroup, there are 3 group_number but for some reasons, v$asm_disk is not showing group_nmuber 1 (ARCLOG Disk Group)

SQL> select group_number,name,total_mb/1024,free_mb/1024 from v$asm_diskgroup;

  GROUP_NUMBER NAME            TOTAL_MB/1024   FREE_MB/1024
-------------- -------------- -------------- --------------
             1 ARCLOG           136.71484375 136.1806640625
             2 DATA           838.1220703125 717.8642578125
             3 FRA              419.16796875   198.17578125

SQL> select group_number,disk_number,name,total_mb/1024 from v$asm_disk;