Our science is focused on fluid venting at isolated seamounts in the deep ocean as analog environments to hydrothermal systems on other Ocean Worlds. A major reason why Ocean Worlds such as Enceladus are thought to be habitable is the likelihood that water-rock reactions at their seafloors yield chemical reductants that, when combined with oxidants in the overlying ocean, provide redox couples that are energetically favorable for sustaining microbial metabolism. The discovery of plumes erupting from the surface of Enceladus during the Cassini mission has provided opportunities to constrain seafloor conditions there. Specifically, the presence of silica nanoparticles inferred to derive from Enceladus has been used as evidence for hydrothermal circulation at the seafloor at ~50-200°C. These water-rock reactions have guided associated predictions of the pH and redox conditions on Enceladus. To date, however, the primary Earth analog invoked for these Ocean World hydrothermal environments is mid-ocean ridge venting and associated activity at plate boundaries where maximum temperature ranges are typically 350-400°C. However, the driving force for these ridge systems is mantle convection, which may not manifest in a similar way or even exist on other Ocean Worlds, raising questions about the appropriateness of ridge-crest hydrothermal systems for predicting habitability on Ocean Worlds that lack plate tectonics.

The SUBSEA team will investigate intra-plate submarine volcanoes are important and relevant analogs to consider, and may challenge assumptions that mid-ocean ridge data impose on our models of Ocean World energetics and associated habitability predictions. These seamounts host a distinct class of lower-temperature (<150°C) fluid flow systems that have been comparatively overlooked on Earth, but which may be a particularly pertinent analog for any other Ocean World that possesses discrete seafloor volcanism regardless of planetary-scale tectonics. Furthermore, the conditions anticipated for Enceladus (T=50-200°C; P=10-50 MPa) coincide closely with those reported for submarine intraplate volcanoes.

In 2018, the SUBSEA team will explore an underwater volcano, called the Lō`ihi Seamount, which is off the eastern coast of the Big Island of Hawai`i. This seamount will be investigated as an analog of putative hydrothermal systems on the seafloor of Enceladus and other Ocean World systems. The team will be characterizing and systematically sampling across a range of pressures and temperatures at Lō`ihi Seamount. Existing and newly collected data from Lō`ihi will provide scientists with an opportunity to test predictions about the habitability of seafloor hydrothermal systems under a range of conditions that extend beyond the well-studied systems at mid-ocean ridges.

The SUBSEA team will conduct our scientific fieldwork from the Exploration Vessel (E/V) Nautilus, which is equipped with the Hercules and Argus ROVs. Ship-based human operators are provided scientific support and exploration direction by a remote Science Team that is connected to the Nautilus via a telepresence-enabled communications infrastructure control these ROVs under low latency feedback conditions.