Here is the full list of all 23 Ski-Doo Snowmobile Challenge achievements worth 1,000 gamerscore.
Unlock all unlockables in career mode.
Perform a double frontflip (Not achievable in splitscreen).
Stay airborne for 5 seconds (Not achievable in splitscreen).
Perform a double backflip (Not achievable in splitscreen).
Stay in adrenaline mode for 60 seconds (Not achievable in splitscreen).
Stay in adrenaline mode for 30 seconds (Not achievable in splitscreen).
Perform a three stunt combo (Not achievable in splitscreen).
Unlock half of all unlockables in career mode.
Collect $50000 in career mode without spending them.
Collide with 3 trees in a race (Not achievable in splitscreen).
Take down four opponents in a row without crashing (Not achievable in splitscreen).
Take down three opponents in a row without crashing (Not achievable in splitscreen).
Lead a race from start to finish (Not achievable in splitscreen).
Hold a stunt for 4 seconds (Not achievable in splitscreen).
Perform a two stunt combo (Not achievable in splitscreen).
Collide with the spectators (Not achievable in splitscreen).
Perform a frontflip (Not achievable in splitscreen).
Stay airborne for 3 seconds (Not achievable in splitscreen).
Hold a stunt for 2 seconds (Not achievable in splitscreen).
Perform a backflip (Not achievable in splitscreen).
Win a career race with your sled intact (Not achievable in splitscreen).
Land on top of another player (Not achievable in splitscreen).
Take down one opponent (Not achievable in splitscreen).