Since the last update we have conducted three ROV dives.

First we continued where we left off on the last dive: exploring the southern detachment termination. We made another southwards zig-zag traverse across the contact between the corrugated surface and the area to the east of it.

In the relatively flat terrain of the corrugated surface, we utilize slope maps to identify probable outcrops before diving. These maps we generate from the AUV bathymetry, often in a rush between the recovery of the AUV and the ROV dive hours after.

Since steeper slopes are less prone to sediment accumulation, they are often the most likely to have exposures of rock (in theory). These maps enable us to be very efficient in the way we use our cruise time – with clearly identified targets at the seafloor beforehand.

We then proceeded west, away from the termination of the corrugated surface. Here we searched for outcrops along the ridges with the most prominent slopes, and we also tried to identify the source for some other microstructures in the bathymetry. Then we turned north and made a profile perpendicular to the E-W trending ridges.

In addition to the ROV dives, three dredges has also been done on the southern part of the 13°20’N detachment. For the most part these dredges have been close to full.

Tonight we dive on the northern tip of the detachment. 

Today we dove in the eastern area of the 13°20’ detachment. Previous to the dive Abyss AUV surveying provided us with detailed bathymetry maps. Combining these with sidescan sonar maps, we were able to pick out good targets for the dive.

Our investigations started on the detachment toe, where the sidescan sonar show a strong reflection.  In order to figure out the nature of the contact between the striated surface and the rocks to the east of it, we made a thorough zig-zag traverse along the contact. 

The next objective was trying to uncover the nature of the corrugated surface. We made a westwards traverse along the ridges and grooves, where we recovered rock samples.

Now we are deploying Abyss for further mapping of the 13°20’ core complex. Later tonight we are diving further south on the same contact.

In the first dive we revisited the chimneys at Semenov 2 on the summit of the 13°30’ N detachment. This dive explored this hydrothermal vent system, and during the dive fluid samples and rocks where collected by VICTOR. 

Next day we conducted a geological exploration dive at the western part of the detachment. Starting from the base of a scarp near the axis we proceeded up slope, to reach a fault scarp where the rocks from the detachment were exposed, giving us a great target for sampling and looking into this massif. A final dive is planned to investigate the top of the massif tonight, at the limit between the striated surface and the seafloor to the W, and to better understand what causes these striations. 

For the first and second ROV dive we relied on the ship’s bathymetry for selecting dive targets. For future dives we will do AUV surveying prior to ROV dives, as these provide us with metre-scale bathymetry, significantly more detailed than the hundred metre-scale maps that can be acquired from a ship. Hence, features on the seafloor that can be then seen and recognized with Victor can be explored in detail. Any chemical anomalies from hydrothermal systems can also be detected by Abyss, using a variety of sensors to `sniff’ the seawater it passes through. Eventually, these sensors will allow us to the location of any active hydrothermal field prior to diving with Victor.  

The next dive was a long traverse across the detachment at 13°30’N, from its eastern termination in the axial valley across much of the corrugated, striated surface of the massif. VICTOR was deployed on the hanging wall, right next to the detachment toe, before continuing over on the footwall of the detachment. This area turned out to be highly sedimented, with evidence of fossil hydrothermal activity. 

Of two fault scarps mapped by Abyss, the first one was covered by talus, and the second gave us some spectacular outcrops. These we sampled and imaged for hours – looking into the core complex. Lastly, we traversed west to explore the nature of the E-W trending corrugations on the detachment, and hydrothermal mounds over it.

The next dive focused on the ridges between the 13°30’ N and 13°20’ N detachments. Exposed along the scarps of large faults we found basalts. 

Now while Abyss is collecting bathymetry from the 13°20’N detachment, we are going to conduct our, for the moment, last ROV dive at the summit of the 13°30’N detachment. We will then move our investigations to the southern dome.

At 21:00 today we did our first ROV dive.

An E-W trending chain of five hydrothermal vent fields (Semenov 1-5) has been located in the area, though only one, Semenov 2, has been inferred to be active (Beltenev, 2009).  The main purpose of our first dive was to locate, characterize and sample this active venting.

VICTOR was deployed in the northern part of the 13° 30’N core complex, then following a scarp uphill southwards towards shallowest point of the complex. We recovered basalts and metabasaltic rocks, serpentinized harzburgite and pieces of anhydrite chimney as we proceeded along the track. 

On the top of the slope we encountered shells of dead mussels indicating the proximity of hydrothermal activity where they live. Upon following this trail of mussels, we discovered an active, ~4 m high hydrothermal mound covered with white bacterial mats. Several smaller diffuse flows were also observed around the main chimney. 

In the main vent temperature measurements of hydrothermal fluids of > 300 °C were recorded. Samples of fluids and vent fauna (mostly shrimps) were recovered. Parts of the chimney itself were also sampled. We also deployed autonomous temperature probes in the main vent and in a diffuse flow nearby, and we will recover them towards the end of the cruise.

Upon surveying the surrounding area another black smoker vent was found, and surely other vents do exist around this area.

The AUV (Autonomous Underwater Vehicle) "Abyss" was deployed for the first time today. We had two rounds of testing, one during the day and one in the afternoon.