Four NASA Astrobiology Institute (NAI) scientists from three different NAI teams have joined the Integrated Ocean Drilling Program (IODP) Expedition 331 to the Iheya North hydrothermal field of the Okinawa Trough. This international expedition will use state-of-the-art drilling techniques to look for direct evidence of the active and diverse microbial ecosystems hypothesized to thrive deep beneath seafloor hydrothermal vent systems. This “Deep Hot Biosphere” expedition aims to study the physical, geochemical, and hydrogeologic parameters of the Okinawa Trough subseafloor and its endemic microbiota. The work is highly relevant to the field of Astrobiology because the hot subseafloor in this volcanic province is an extreme environment potentially similar to important habitats on the early Earth, and to hydrothermal systems that may have been important for the origin of life. Understanding microbial life in this type of environment will provide critical information regarding where such life can flourish throughout the cosmos. For this work, the NAI teams will be working with an international science team on the Japanese research vessel Chikyu operated by CDEX and with Co-Chiefs Ken Takai (JAMSTEC, Japan) and Mike Mottl (University of Hawaii NAI team). The other three NAI scientists are Leah Brandt (Penn State), Hilairy Hartnett (Arizona State University), and Chris House (Penn State). IODP is managed by IODP Management International with funding from a number of different agencies including the Ministry of Education, Culture, Sports, Science and Technology (Japan) and the National Science Foundation (United States).