2004
RAS fluid intake funnel in place at Virgin Vent. Visible are the excavation
tool, HOBO and temperature sensor (T1) at the base of tripod (counter-clockwise
from lower left). New RAS is in the background.
Dive R854 was largely devoted to recovering the 2003 RAS (Remote Access
Sampler) and replacing it with 2004 RAS. The new RAS is essentially the
same as last year's model but has an additional sensor for Eh (a redox
measurement of electron movement). The new RAS had been dropped to the
seafloor the previous day from the Thompson and ROPOS had to move it into
its final position. The 2003 RAS first had to be nudged to the surface
by the ROV as it had been caught on a thin line when given its release
signal. After placing the new RAS, ROPOS then positioned the intake funnel
and temperature probe over the vent where the anhydrite chimney had formed
the prior year. The anhydrite chimney had been knocked over on yesterday's
dive when recovering the old RAS and after only a day, more anhydrite
deposits were being formed.
The
remainder of the dive was devoted to recovering and deploying long-term
temperature sensors, and collecting digital images of several vents (Mushroom,
Hell, and Phoenix). One HOBO (high temperature probe) instrument was placed
at Virgin, another recovered at Marshmallow and a suction sample of blue
microbial mat was made at Phoenix vent.
