HA won't boot after power outage

Power was turned off this morning and when restored, HA no longer boots. I can ping the box, but cannot ssh to it.

It’s a raspberry pi - monitor attached shows after ~20 seconds

Welcome to Home Assisstant
hassio : login

then sits in a display loop repeating the same message sequence every 15s or so.

I know the card may be corrupted, but is there any way to recover / diagnose. Don’t believe I have a recent snapshot - at least I thought I’d turned on snapshots, but not sure where they would have been stored…