Bitcoin Prizes - How to keep secure?

Hi all,

Suppose I want to establish a prize to encourage space exploration. I get NASA to agree to create a small compartment on their next Mars rover, which I am allowed to place a few small objects into before launch. I want to somehow create a public/private keypair, and place the private key into the compartment in some way (paper key, USB drive, metal engraved key). After the rover is launched, I announce what I have done, along with the public key. Interested bitcoin users then can fund the Mars Bitcoin prize by sending payments to the public address. The first person or group to get to Mars on their own, find the rover, and open the compartment gets the private key, and thus the prize.

Now obviously, some will suspect that I somehow kept the private key, and will simply steal the prize once the funds accumulate. This suspicion will decrease the number of potential funders of the prize, and create acquisitions against me, which I don't want either.

So the question is, in exactly this scenario, how can I or a group of people best generate the keypair and place the private key into the compartment while assuring to everyone else we did not retain the private key? I have thought about rolling cameras during the whole process, purchasing a new computer on camera, etc., but there will always be suspicion.

Also note of the key options I have mentioned, I would highly prefer the metal engraving. The USB key may get destroyed by radiation, and the paper may burn if containment systems fail.