A 2-day International RETH Workshop was held at Purdue University on October 22 and 23, 2018 to discuss the realistic challenges and opportunities associated with extraterrestrial habitats. In addition to engineering and planetary science issues, human factors researchers were involved to discuss concerns regarding the planning for such an effort. As we envisioned, over 60 attendees participated in the workshop. Also, 21 speakers (2 international, and the rest from the U.S.) presented on a range of topics from various academic institutions, industry and NASA. Strong participation of Purdue personnel, including Faculty, Post-Graduate Researchers, and students at all levels was observed.