Today is the day… the day we will finally see some black smokin' hydrothermal chimneys! ROPOS is currently on its way down to the ASHES vent field, a site in Axial caldera with 7-8 hydrothermal chimneys. We are also going to unload the Sensor Bots and high speed camera ontot he sea floor, where they will be left for the next 5 or so days to blink their deep sea code, relaying information on temperature, pH, dissolved oxygen, ambient light and optical back scatter. This new technology is the start of the development of an array of deep-sea-sensing bots, that will provide invaluable information on ocean chemistry and the response of oceans to events such as the volcanic eruption that occurred at Axial Caldera in April.
Yesterday, ROPOS was used to survey the new lava flow in Axial Caldera – in some places, there is a 10m difference in height between the old flow and new flows! The cameras revealed many beautiful images of fresh, glassy basalts, pillow lavas, and multiple large collapse ponds and pillars. The orange colorus from oxidizing iron contrast beautifully with the black basalt under the light of the camera. We also came across a snow blower, a type of vent that forms after recent volcanic eruptions.
When not on ROPOS watch duty, I've been helping prepare the Sensor Bots for deployment, as well as aiding with, hydrogen, helium and methane sampling for fluids collected from CTDs (CTDs are used to collect water from hydrothermal 'plumes' – hydrothermal fluid that has mixed with the overlying seawater). The helium sampling process is pretty fun – the fluid taken for this gas has to be sealed in copper tubes to ensure that it is not contamined by atmospheric gas. We made the sample containers by cutting 1/2" copper tubing into 2' sections. On each section, we then flattened two 3" sections to ~5/16". Once filled with water, we re-roudned the tube. This created a vacuum in the tube, which we could use to ensure a sound seal of the water within the tubing, which is essential for accurate determination of the He concentration in the water. The helium isotope ratio is an excellent tracer of hydrothermal fluids since the isotope signature of the fluid is different from the isotope signature of the atmosphere. Isotopes are atoms of the same element, that have varying masses due to different numbers of neutrons in the nucleus. This causes them to behave differently in chemical and physical reactions, with light isotopes usually reacting faster than heavy isotopes. Different reservoirs of the element (for example the atmosphere, the ocean, and the subseafloor) can therefore have different isotope signatures as a result of the varying processes that occur bettransfer the element between the different reservoirs, causing the isotopes to fractionate between reservoirs. Since helium is not used in any reactions that occur within the ocean, (it's 'conservative') the signal of the hydrothermal fluid can be traced for miles. The helium samples will last for weeks inside the copper tubing, and will be taken to labs on land for analysis.
Aboard the ship, we can measure the methane and hydrogen concentrations using gas chromatography (GC). To remove methane and hydrogen from seawater, we first inject pure helium into the sample, providing air space for the tiny methane and hydrogen gas bubbles to escape into. Pure helium is run through the GC as a 'blank' gas – the sensors don't read it's presence, and it is just used to carry the hydrogen and methane through the 'column'. The column – is actually a long, narrow, hollow coil. We inject the methane and hydrogen gas (mixed with helium) into the GC and due to the difference in 'stickiness' and mass of hydrogen versus methane gas, they run through the coil at different rates, allowing them to separate. Sensors on the other side then measure first the concentration of hydrogen and then the concentration of methane as they exit the column. Hydrogen and methane are also excellent tracers of hydrothermal fluid – they can be used to determine the original source of the fluid and processes affecting it, as well as how old the hydrothermal plume they were sampled from is.
Alright, I'm sure you would love to read about more science, but there is lots else going on here as well! My hat is coming along quite nicely. I had an amazing lose in scrabble the other night to Sarah, one of the resident champions. There is a hammock set up at the bow of the boat which I use as my nightly star gazing spot – two nights ago I saw the biggest shooting star I have ever seen! The bow is also a great place to stretch out and lie in the sun. There are also many guitarists on board for musical entertainment, and a gym! Try running on a tredmill on a boat rocking side to side, in a room that is barely tall enough to fit you…. when the boat goes down on an up, watch out for your head!
There are so many people on board here who have traveled all over the world either as crew and cooks for various ships or other operations, or as scientists – it's such a great place to learn about and share experiences. I am continuing to have a great time abord the Thomas G. Thompson!