April 28th, 2003; Leg 5, Day #8
Success! The Raman project made an
important transition today toward evolving the laser
Raman spectrometer (LRS) into an expeditionary tool when it completed
the first in situ measurements of a natural sample on the seafloor.
MBARI’s LRS made its debut last year as the first-ever deep-sea system,
and those experiments analyzed known lab samples to verify system
function. Today the LRS successfully measured spectra of hydrocarbon gas
venting from the seafloor at a site 1580 meters deep in the Guaymas Basin.
The research team of Peter Brewer, Sheri
Kirkwood, and Ed
Peltzer are very excited by the results. They learned what
manipulations were required to conduct the experiment and what
sensitivities to expect in the measurements. The ROV
Tiburon system delivered the data flawlessly, and the pilots
displayed their skill in performing the unusual handling protocols
required. The dominant spectral peaks in the data correspond to a methane
signature, the main constituent of the vent gas.
was launched into the water early this morning after the LRS and heated
funnel instrument were placed into its benthic drawer. The ROV descended
to a gas vent site that we have been studying, now dubbed “Pinky’s Gas
Vent” for the plastic flamingo lawn ornament that adorns the site (see
right). Sheri and Bill
monitored the LRS software system in the dry lab. Peter and Ed were in the control room noting the ROV data, videotapes, and coordinating the ROV movements. All communicated across the ship’s phone system, with bantering back and forth between the two areas throughout the day. There was a moment of suspense when Tiburon unexpectedly reset its control system. All functions turned off and the cameras went black. The pilots quickly responded to the situation and soon had everything under control. The LRS was powered on again with no ill effect.
Pinky's gas vent site. ROV Tiburon's manipulator arm is ready to grasp the heated gas funnel instrument to begin collecting gas from the vent. The laser light glows green in the sample box. The skin of methane hydrate within the box did not contaminate the sample as no water signatures were seen in the spectra.
The experiment involved a series of painstaking steps that each required waiting time. The overall procedure included making background measurements with the LRS, using the heated funnel to collect a gas sample from the vent, maneuvering the funnel to a sample box at the end of the LRS, tipping it delicately to transfer the gas into the box, and acquiring data about the sample from the LRS. The added step of emptying the gas funnel sample into the LRS box was a difficult maneuver. On only the second try, ROV pilot Buzz Scott successfully transferred the sample to the box. Sheri called “We've got some gas!” from the lab as the LRS data showed a methane peak. Each measurement step took several minutes during the data acquisition, with the final phase lasting nearly 2.5 hours. The glowing green laser light of the LRS system was all that could be seen for those long stretches as the vehicle's lights had to be turned off for the experiment.
Sheri White studies the spectral peaks as the LRS system acquires data. Bill Kirkwood looks on.
recovered in mid-afternoon, and the ship moved to a new location. The
purpose of this dive was to search for another gas vent. Charlie
Paull studied the muddy and nearly featureless seafloor as Tiburon
flew over it. He found no evidence of vent activity on the seafloor or on
the scanning sonar. There was much discussion in the control room after
the dive about where to look next.