International District Complete

With good weather, we are making rapid progress in completing all major tasks planned for the summit of Axial Seamount during Leg 1. Yesterday, upon completion of the Central Caldera geophysical Site, we made a full court press on a major hydrothermal experiment at the International District 1 Site. Tonight, we deployed and installed all instruments and cables within this hydrothermal field — the main sensor installation is at the vent called El Gordo, which we surveyed yesterday for instrument placement. During the evening last night, the fluid – microbial DNA sampler was lowered on the ship's trawl wire to the seafloor – in total, this sampler's mooring stands 60 ft in height.

It is always a good day when you get to see the extreme environments and the weird life that thrives at hydrothermal vents. ROPOS took the digital-still camera and the pH-H2S-temperature sensor down to the field in the tool sled latched under the vehicle. The mass spectrometer (middle instrument in the image above), an instrument that will measure gas concentrations (e.g., methane) in the diffuse vent fluids, was first installed. This was followed by the remote access fluid and microbial DNA sampler (to the right in the above image) that will provide time-series chemistry of the vent fluids and compositional information about the microbial communities at this vent. A titanium "hat" was placed within a tubeworm bush on top of the El Gordo edifice. Inside this "hat" are temperature sensors and sampling nozzles for the vent fluid and microbial DNA sampler. The cap prevents significant seawater mixing with the end-member hydrothermal fluids so that we can get undiluted fluids. A small intake nozzle for the mass spectrometer was placed in an opening under the vent cap. Finally, a beautiful underwater digital-still camera was installed (left side of image) that will document the change in vent-fluid flow and animal communities over time at this site.

A huge rattail fish followed the ROV for much of the dive – this is the largest fish we have ever seen at this site – at the end of the dive it seemed particularly curious about the tool sled basket, coming over to investigate it and at one point almost swimming inside.

Now we are diving at the ASHES hydrothermal field for final installations at the summit of Axial Seamount….Exciting times these are.