The pilot of the tailwheel, ski-equipped airplane reported that while landing off airport in flat light conditions, he was unable to maintain a good visual reference of the hardpacked snow covered landing area. After touchdown, the airplane drifted off the hardpacked snow and the left ski sunk in softer snow. He increased power and attempted to recover with "hard right control" with no prevail. The airplane struck a snow-covered tank with the left ski.
The airplane sustained substantial damage to the left-wing lift strut.
The pilot reported that there were no pre-accident mechanical failures or malfunctions with the airplane that would have precluded normal operation.