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| Deep sea Marmite from 7000m |
Milly: Ugly Fish pt 7
Life on board a research ship can, at times, be rather boring. It is imperative that, to stave off derangement, you make your own fun preferably without damaging yourself or others. We have had a few ideas, after a particularly uneventful evening of mud measuring: 1) Deep sea fish top trumps 2) a horror film featuring a radioactive or chemical spill creating GIANT holuthorians, I'd quite like to call it 'Horrorthurian', not a catchy title and 3) sending weird objects to the ocean floor to see what happens to them.
During my last research cruise Alan very kindly allowed me to place a jar of marmite atop his lander and send it down into the Peru-Chile trench (7000-8000m). Sealed with a plastic top, the marmite was put under an enormous amount of pressure and subsequently its consistency was altered rather dramatically. The top layer became runny like water and at the bottom, set like concrete. I had a great deal of fun digging around in my marmite jar for hours trying to stir it all up whilst an American scientist looked on, grimacing every once in a while when he caught a whiff of its beefy goodness.
So, what does happen to things when they go down the the bottom of the ocean? Well, have a look at this polystyrene cup I put down to 4800m strapped to the lander below. Unfortunately for me, Alan, at 5am, thought it would be really funny if he put it into the bag he had been storing his bait in, before sending it down into the abyss. The reason my cup is now the size of a thimble (and strangely distorted) is due to the effect pressure has on air. Inside the polystyrene lies little air pockets that get compressed with depth, as the pressure increases. The cup is, of course, now also impregnated with mackerel juice, thank you Alan.
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| My polystyrene cup (left) looking rather distorted and how it looked before compression (right) |
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| A previous effort...much better! |
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| Getting slightly more creative....OCUPTOPUS! |
Pressure is measured in pascals (Pa) which corresponds to one newton per square meter (imagine one newton force as the force of the Earth's gravity on an apple). 100kPa (100,000 Pa) is typical air pressure at the surface of the Earth. With every 10m that the cup descends, another 100kPa of pressure is added, constantly squeezing the air into a smaller area until it reaches a point where most of the air is squeezed out of the cup entirely. I've been asked by an alarming number of people whether I will be doing any deep sea diving on this trip. Unfortunately, much like the cup, the air in my lungs would be squeezed out and although this can be rectified by using pressurised air (as with SCUBA diving) to fill up my lungs again, after about 60m the oxygen in the air at high partial pressure would start to poison me, forming reactive species, damaging my cells. Commercial divers are able to reach depths of 100m using gas mixtures with snazzy names like 'hydreliox' (helium, hydrogen and oxygen) or 'neox' (neon and oxygen) which have reduced levels of oxygen and are therefore less likely to cause damage. I say less because there is still the risk of inert gas bubbles forming in the blood or tissues of a diver as they ascend from depth, 'the bends'. It has also been pointed out to me that in carrying enough air for such a trip, I would be squashed like a ripe pear.
At 100m there is 1100kPa of pressure. The deepest living fish ever recorded were at 7.7km (Alan Jamieson, again) where pressure is about 77,500kPa! So how do they survive at these depths under extreme pressure?
I shall explain all in a future post...there is a trawl afoot.
