Von Neumann seeding probe

The von Neuman seeding probe was a genetically engineered probe to either terraform other planets or be used as a weapon. It was named after John von Neumann, a scientist from Earth who theorised about such a creation.

The probe works in three stages. The first is biomass assimilation and consolidation, breaking down organic matter. The more organic matter it can break down the more complex its internal structure can become. The second stage is creating simple constructs using the data it has assimilated. The third is the "enquiry stage", a fail safe to make sure the probe can't knock out an intelligent species. The probe asks a question - explain ratio 1:812 - and if the question is answered correctly then the probe will self-terminate.

About 1000 years before the Doctor was born, the probe landed on Gallifrey and managed to kill about 7000 Time Lords. The Time Lords eventually managed to contain the probe, and to make sure such a catastrophe never happened again they engineered an immunity into their genes.

Not long after 1974, the probe landed on Earth at a place called Fort Casey. It wiped the whole town out, killing every organic thing inside it, as well as three of Major Platt's investigation team. The Eighth Doctor, making use of his immunity, successfully answered the failsafe question and the probe died. (PROSE: Spore)