This market will predict the year when the first extraterrestrially mined material arrives on Earth. The material should be obtained and returned by a private enterprise, not primarily for scientific research, but for sale as a commodity. The venture doesn't need to be profitable or bring back a large quantity of material; it could be a small amount to demonstrate the concept. The market will resolve based on the most authoritative and widely accepted report or data source available after the event.

Possible examples;

Moon mining

Asteroid mining

Material mined from mars and returned to earth