You win some, you lose some

September 8, 2013

It was a frustrating day for the science team today. Although we managed to get in a full day’s ROV dive, we did not end the day with the data and discoveries we had hoped for. We went back to the Eel River Slump area, and targeted the mound right in the middle of the slump, starting very close to the oily, gassy site we worked at yesterday.

MBARI intern Wilson Sauthoff in control room

MBARI intern Wilson Sauthoff controls the ROV’s main science camera while the laser Raman spectrometer is taking a reading. The spectra can be seen at the top right; the various peaks in the graph indicate the presence of different gases. Wilson is beginning a Ph.D. program at the University of California, Santa Cruz, at the end of the month.

We traveled up and over the mound, stopping in several locations to take laser Raman spectrometer readings of the pore water-the water within the sediment on the seafloor. To get accurate and useful data is a slow and painstaking process, taking several hours. The trusty laser Raman spectrometer tripod system, which has worked so well on so many expeditions, did not return any signal of interesting chemical activity in the pore water. Perhaps the tripod was not working properly, or perhaps there truly was no chemical activity of substance there, even though we knew that just 200 meters away on the same mound there was abundant oil and gas. Either way, it was a bust.

elongate mound

The elongate mound in the middle of the larger slump was the target of today’s work.

We moved back to the more productive site, but soon ran into other technical problems that prevented us from getting the Raman spectra profiles from the pore water. When we inserted the probe into a gassy sediment, a bubble of gas entered the optical cell and froze into a solid hydrate, gumming up the works. With the system blocked with a plug of hydrate ice, there was nothing to do but fly the vehicle up to about 300 meters to get the warmer temperature and lower pressure required to relieve the blockage. This took valuable time. When the ROV was back on the seafloor to resume our work and the tool sled drawer jammed, preventing access to our instruments, it was time to call it a day.

tripod with laser

The tripod containing the laser Raman spectrometer pore-water probe is set down in a field of clams. The tripod helps to assure a controlled insertion of the probe (the white rod in the middle) into the sediment.

The science team’s motto of the day: “Some days you’re the windshield, some days you’re the bug.”

— Nancy Barr