Found your article on Planetary Resources during a web search, and wanted to let you know that you have used a term incorrectly: "Planetary Defense" is the proper term for preventing asteroid impacts to the Earth. "Planetary Protection" is the process of preventing biological contamination of other solar system objects, and also avoiding adverse effects to the environment of the Earth due to the introduction of extraterrestrial material. I hope this information is useful.
Sincerely, Catharine A. Conley
NASA Planetary Protection Officer