The Zito probe is a deep Earth probe launched by Giovanni Zito in the fourth book, the Opal Deception. It was released ten years ahead of schedule, and threw Foaly's predictions into disarray. It was able to be used early as Opal Koboi had given Giovanni Zito (whom she had mesmerised) the technology to cut through the crust without "frying half a continent". It was released into a rich high grade (around 80%) heamatite (iron ore) orebody which allowed it to travel to the core at 5 metres a second without being destroyed.