Vixen
vent before and after fluid sampling the chimney. The chimney (before)
was composed of anhydrite which collapsed when touched by sampling
probe (after). Also visible are the HOBOs (high temperature probe),
2003 in both images, 2004 in after. (The 2003 HOBO was recovered after
the photo.)
The day began with the successful recovery of the 2004 BPR. The BPR will
undergo repairs and be redeployed on a subsequent cruise this year.
Dive
857, the final dive of NeMO 2004, began in the 1998 lava flow area. Sites
visited were Marker 113, Bag City, Vixen and Casper.
(See map). Vixen appeared to be smoking more strongly than last year,
the chimney color was darker and the base appeared larger. Scientists
speculate it may be building sulfide deposits although the sampled chimney
was still composed of anhydrite (collapsing when the temperature probe
touched).
ROPOS
transited next to the ASHES vent field to examine the 2004 NeMO Net RAS.
The data obtained from the NeMO Net satellite had indicated a temperature
drop in the instrument since its placement at the Virgin vent. On this
dive ROPOS observed since deployment of the intake funnel, a cluster of
small anhydrite chimney formed underneath the tripod (the site was excavated
bare at deployment). The formation of these chimneys had diverted some
of the hydrothermal fluid flow away from the funnel so ROPOS repositioned
the instrument for a more direct fluid intake. The last vent visited on
this expedition was Hell vent where the final samples were taken.
The
dive ended with the successful discovery of a Rumbleometer instrument
that had been deployed in 1999 but never recovered. Rumbleometers are
used to measure seafloor earthquakes. The location was marked for a future
recovery of the instrument.
