Unintended seafloor sampling

We completed deep-towing our second profile today and brought SUESI back on deck around lunch time.  Samer told me that two days ago during the tow down the continental slope they had an unintended low altitude event on the Vulcan receiver that is towed on a tether 500 m behind SUESI, and that it likely had scraped the sea bottom. Sure enough, the Vulcan receiver came back up today with its nose electrode pushed in about three centimeters with the pipe full of seafloor mud. The acoustic relay transponder towed behind it also had a small fan shaped plant attached it. We haven’t seen any animal or plant life on the instruments yet other than jelly fish tentacles so it was  nice to finally see evidence of life on the seafloor.  We also discovered some corrosion on the back half of SUESI’s pressure case on the unpainted but anodized sections. Steve thinks something may have come loose inside and is shorting current to the pressure case; that current travels out the easiest paths, which are the non-painted parts of the pressure case, where it electrochemically corrodes the aluminum. This is the first time we’ve seen this on SUESI in its ten years of service, so we’re planning to switch to the spare SUESI for the final two planned deep-tows. Photos from today below.

Goran watching one of SUESI’s copper electrodes being brought back on deck.
Reeling in the final section of SUESI’s antenna which is terminated with a 50 foot long copper electrode.
Some of the white corrosion on the aft half of SUESI’s pressure case on both the edges of the seal screws and the gap in the main cylinder.
The Vulcan towed EM receiver back on deck. Note the mud inside the nose electrode’s tube.
Plant that was scraped off the seafloor in about 1700 m water depth during the Vulcan’s low altitude event.