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I'm Katie rembert I'm a second year PhD

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student here at Colorado Boulder working

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with Alexis Templeton as part of the

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rock powered life nei team and today I'm

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going to be presenting some of my

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initial work on geologic and hydrologic

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controls on the habitability of

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terrestrial serpentine izing

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environments and so now you're probably

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all very familiar with the serpent

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anization reaction but this is really

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the core geologic process that's behind

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my research and like Hannah mentioned

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what I'm really interested in is the

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oxidation of iron coupled to the

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reduction of water to form hydrogen gas

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because as is as you can see here from

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this electron tower that hydrogen is a

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powerful reductant it can act as a

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strong potential electron donor for

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microbial metabolism and of course this

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has great astrobiological implications

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we have detected serpentine on noachian

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age outcrops on Mars and from

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geochemical modeling of the plumes from

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Enceladus we believe that the ph of the

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subsurface ocean is 11 or 12 which could

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only be explained by serpentinization

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processes and so if serpent anization

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did happen in the geologic past in

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either Mars or Enceladus that suggests

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potential habitability of these

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environments and so I want to just bring

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up the definition of habitability

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traditionally in astrobiology you'll

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find a binary definition and so in this

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review paper by Kyle at all in 2016 and

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astrobiology Journal they say the

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ability of an environment to support the

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activity of at least one known organism

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and so on earth this definition doesn't

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work quite as well and so if you're

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comparing the Amazon rainforest to the

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Atacama Desert yes they are both

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habitable but there's varying degrees so

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the auto comet desert is not as

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habitable as the Amazon rainforest and

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so habitability at least on earth is a

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continuum life is ubiquitous

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and the distribution of life varies as a

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function of geology chemistry and

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physics these controlled amount of

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energy the amount of nutrients chemical

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compounds such as water that's available

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to life and so one of the aims of this

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work is to be able to use geologic and

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hydrologic controls to try to predict

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how that would influence the

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habitability of an environment so in

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trying to plan a mission where would you

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want to search for life what would be

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the most habitable environment within a

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terrestrial astre Penton izing ecosystem

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and so my natural laboratory is this

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mail if you light in oman oman is

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locates located southeast of Saudi

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Arabia and the Arabian Peninsula and

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here's Hannah mentioned we have oceanic

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crust Olga Bros and upper mantle

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prototypes that were emplaced on to the

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continent during the Cretaceous and you

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can kind of see a resemblance to an

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extraterrestrial environment with the

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smell a few light in the top image here

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and you can see there's very little

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plant cover and it's a very arid climate

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and so in Oman we have a unique

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opportunity to sample deep subsurface

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fluids domani government drilled Wells

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into the ophiolite in search for water

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resources for their country which was

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not successful because most of these

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waters are above a pH of 11 but these

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wells span the crustal mantle transition

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and so I've labeled the wells according

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to the rock type that they are located

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in and so we are able to sample various

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lithologies both gabbro and prototype

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across various hydrological regimes and

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I've labeled contact wells here in pink

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I distinguish these separately because

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they sit right between the gabbro and

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the pretty tight so it's difficult to

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tell what the water is actually reacting

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with and so in these wells we use a deep

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submersible pump to retrieve deep fluids

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for geochemical analysis and then we

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also filter five to ten liters of fluid

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to concentrate biomass so that we can

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sequence the DNA of any organisms that

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are living in the subsurface and so what

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we see at least geochemical e is highly

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variable chemistry and so I show here a

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principal component analysis of

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geochemical parameters that were

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measured all three years of our sampling

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we only sample 12 wells but we were

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turned in the winter for three years so

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we have a total of twenty deep well

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samples and I plotted the variable

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loadings as vectors on this principle

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component analysis to show the

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relationship of each of these chemical

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parameters to the first and second

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principle components and so principal

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component one explains 52.3 percent of

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the variance and what you see is kind of

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these fluid chemistry's parsing out

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based on chemistry to the right you see

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a higher pH calcium rich fluids which I

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labeled here as alkaline prototype which

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can be distinguished from the pink

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pretty tight reacted fluids that are

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more silica rich and have a much lower

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pH and so and so this variable

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geochemistry can easily be explained by

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differences in depth and extent of water

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rock reaction and so in the shallow

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subsurface you would have weathering

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reactions in contact with atmospheric

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oxygen and carbon dioxide and so you

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would whether your magnesium bearing

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minerals enriching fluids and magnesium

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and bicarbonate and as Hannah mentioned

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you're also increasing the pH these

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weathering reactions consume protons and

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at least in the shallow subsurface this

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brings a pH to about eight or nine but

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if these fluids percolate deeper and

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lose contact with the atmosphere this is

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when we really sea serpent anization

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processes happening your magnesium is

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preferentially going into secondary

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minerals such as serpentine and brew

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site so your ritching fluids and calcium

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you're increasing the pH to about at NRL

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to about 10 and 11 maybe 12 and because

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of that most of your di

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see is in the form of the carbonate

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anion and no longer bicarbonate and so

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you can precipitate out carbonate

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minerals and this really lowers the

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dissolved inorganic carbon concentration

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which would impact biology would be

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really hard to fix carbon if there's not

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much carbon to fix and I just want to

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point out that most of the previous work

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in these terrestrial systems has focused

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solely on where these deep fluids

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re-emerged at the surface and seeps in

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contact with oxygen so the work I'm

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doing really expands a habitability

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assessment not only into the subsurface

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but i was looking at highly variable

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fluid chemistry and not just focusing on

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fluids that are ph 11 and 12 and so i

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end up seeing very diverse microbial

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communities don't worry i'm not going to

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go into particularly what organisms we

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see i just want to point out that we can

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predict at least somewhat what

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metabolisms might be occurring in the

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subsurface and from the looks of just

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looking at the what organisms that are

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there potentially we have hydrogen

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oxidation meth an agenda TSA's osita

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genesis sulfate reduction fermentation

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denitrification so very diverse

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metabolisms and just to point out we do

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see life so this isn't at a surface

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system where we have oxygen providing an

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accident these are probably very

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stressed fluids and we are easily able

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to sequence the DNA just using a basic

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power soil DNA kit concentrating just

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five to ten liters of fluid we can get

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great results but there are huge impacts

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on diversity with pH and so here I've

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plotted pH versus richness richness is

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just the total number of microbial

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species detected in a sample and as you

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can see there's a strong negative

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correlation we can't say this is a

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causation because pH co varies with a

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lot of other geochemical parameters such

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as calcium but you do know that these

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the ph of the fluids that you sample has

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a good indication of what type of

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diversity you might see and as you would

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expect different fluid chemistry's host

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different my

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Chromeo communities I show here an N MDS

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plot to ordinate the samples based on

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microbial community similarities so

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samples that plot closely together have

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more similar communities than samples

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that plot very far and the size of the

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sample point it correlates to the

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richness and so what we see from this is

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that geologic context and the extent of

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water action really control the

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microbial ecology our elkland prototype

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the shallow reaction and the gabbro have

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very similar communities which makes

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sense because on the principle component

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analysis geochemistry they plotted right

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next to each other we saw that the hyper

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elkland prototype fluids had a very

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disparate geochemistry and they plot on

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the opposite side of this ordination

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they have a very different microbial

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communities but I think most

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interestingly is that these contact

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fluids which on the PCA had a very

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variable geochemistry actually have a

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very unique microbial community

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composition compared to any other fluid

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type and so just to bring this all

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together and kind of expand a Hydra

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geochemical model of habitability there

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are a few sites of interest so in this

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study we sampled the shallow prototype

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fluids and deep fluids but we didn't

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really capture a transition so we just

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have these two end members but

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theoretically somewhere in the

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subsurface you have to have a transition

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from a more oxidized fluid to a more

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reduced and that would be very

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interesting biologically because that

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chemical disequilibrium would provide

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energy for microbial metabolism so in

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the future we're trying to find Wells

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and hopefully with a Mon drilling

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project maybe we can drill well that

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captures some of the microbiology in

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those transitional fluids but also as I

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just mentioned I am interested in these

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contact fluids so I have added gabbro to

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this Hydra geochemical model and at

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these contact fluids you have a huge

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change in permeability so gay bros are

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much more permeable you have these deep

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hyper elkland prototype foods injecting

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into gabbro which is facilitating mixing

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and again that's chemical disequilibrium

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that could support life and during this

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injection you're actually

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forcing these fluids up to the surface

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so astro biologically if you're looking

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at a serpentine outcrop on Mars and you

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see a contact between pretty tight and

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gabbro maybe that's a place where you

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would potentially find near-surface bio

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signatures and with that if any

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questions questions for Katie the risk

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of something obsessive I stucco mamonas

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and reach that high pH in your cultures

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to learn so I'm thinking maybe there's

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something interesting there when you

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look at the 16s yeah you see when you go

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to the higher pH is you have more

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abundance of coma Mona's compared to the

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other which is exactly what Stu the seed

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and I thought it's interesting the coma

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Mona Dacia the three you at higher pH is

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the same thing as your isolates yes so

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there does seem to be at least for my

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dad I didn't go into this and this talk

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but a core similarity to at least these

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deep hyper alkaline prototype fluids to

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other serpent enticing systems and even

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to trust us repented izing seeps but i

284
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actually do see i guess some species

285
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that aren't commonly associated with

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00:12:33,130 --> 00:12:30,980
other trust Joe serpent izing systems

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00:12:35,950 --> 00:12:33,140
like thermode a self over B Rene say and

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mayo thermos may a thermos has found its

289
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surface heaps and thought to be aerobic

290
00:12:41,590 --> 00:12:39,320
but I only find it in my deep fluid so

291
00:12:42,760 --> 00:12:41,600
it's interesting there is a core

292
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similarity but there's also a lot of

293
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differences to what other people are

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00:12:47,860 --> 00:12:46,130
seeing and yeah I'm one more question

295
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attention one more question is the rota

296
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cycle each other to detect in the NS HQ

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00:12:57,190 --> 00:12:52,670
do you know the characteristics of that

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00:13:04,510 --> 00:12:57,200
site and I say to you which one 410 and

299
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it's HQ 10 no I do not well NS HQ

300
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tenants a contact well we do weren't

301
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able to measure any reduce software

302
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species as some of those roto cycle ACR

303
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I'm involved in software cycling but

304
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that's like a pH of about eight

305
00:13:23,380 --> 00:13:21,170
okay yeah and what dude can you have an

306
00:13:26,620 --> 00:13:23,390
idea of what so there could be hydrogen

307
00:13:31,000 --> 00:13:26,630
oxidation coupled to metal reduction

308
00:13:33,880 --> 00:13:31,010
there so in most of these lower ph foods

309
00:13:35,620 --> 00:13:33,890
it seems like you have nitrate as the

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primary electron acceptor but you could

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have hydrogen oxidation coupled to

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nitrate but we don't actually detect

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hydrogen in the that fluid but it could

314
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be below the detection limit drawn down

315
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by microorganisms thank you I may be

316
00:14:03,730 --> 00:14:02,360
confusing concepts and maybe reaching a

317
00:14:05,440 --> 00:14:03,740
little bit on this one but I'm just

318
00:14:06,970 --> 00:14:05,450
noticing that as you were mentioning

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there was a correlation is saying that

320
00:14:12,310 --> 00:14:09,020
the authentic relation saying that there

321
00:14:14,800 --> 00:14:12,320
was more biodiversity at lower more

322
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acidic ph s and i realized that they may

323
00:14:19,750 --> 00:14:17,600
have more ideas may have more hydrogen

324
00:14:22,360 --> 00:14:19,760
concentrations and the hydrogen has

325
00:14:24,760 --> 00:14:22,370
electron donation is there a reason why

326
00:14:26,910 --> 00:14:24,770
a high electron donation and or hydrogen

327
00:14:30,670 --> 00:14:26,920
would actually be an increase of

328
00:14:33,010 --> 00:14:30,680
actually a biodiversity per se so it's

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00:14:34,660 --> 00:14:33,020
hydrogen gas that's the great electron

330
00:14:37,540 --> 00:14:34,670
donor for metabolism we see that in the

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really high ph fluids but for as for pH

332
00:14:41,440 --> 00:14:39,170
being at a high pH is really stressful

333
00:14:44,530 --> 00:14:41,450
for microorganism you need a proton pump

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to be able to have metabolism and so

335
00:14:50,140 --> 00:14:47,390
somehow they're having to compensate for

336
00:14:54,190 --> 00:14:50,150
the lack of protons in those fluids to

337
00:14:57,550 --> 00:14:54,200
be able to live at all and so when i say

338
00:15:00,490 --> 00:14:57,560
more it's there still elkland so it's

339
00:15:02,320 --> 00:15:00,500
like a ph 8 to 9 but that's way less

340
00:15:04,570 --> 00:15:02,330
stressful to my our microorganism you'd

341
00:15:06,310 --> 00:15:04,580
expect many more microorganisms to be

342
00:15:18,870 --> 00:15:06,320
able to adapt to that type of setting as

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thank you thank you add a related

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00:15:26,710 --> 00:15:24,530
question i was wondering in terms of

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00:15:29,140 --> 00:15:26,720
diversity is there a cut off into

346
00:15:31,930 --> 00:15:29,150
revocable threshold when you go below

347
00:15:34,630 --> 00:15:31,940
the ph's that you showed today in terms

348
00:15:36,270 --> 00:15:34,640
of large amounts of diversity what do

349
00:15:38,230 --> 00:15:36,280
you see in terms of the more acidic

350
00:15:40,570 --> 00:15:38,240
systems that you're not necessarily

351
00:15:43,450 --> 00:15:40,580
looking at in this study so i would say

352
00:15:45,370 --> 00:15:43,460
usually phu in most environments you

353
00:15:46,990 --> 00:15:45,380
wouldn't see such a gradient of pH and

354
00:15:49,810 --> 00:15:47,000
pH wouldn't necessarily be your

355
00:15:51,400 --> 00:15:49,820
controlling factor so this is a system

356
00:15:54,400 --> 00:15:51,410
or look talking about an oligotrophic

357
00:15:56,080 --> 00:15:54,410
groundwater system there probably isn't

358
00:15:58,870 --> 00:15:56,090
a lot of organic carbon we did measure

359
00:16:02,080 --> 00:15:58,880
organic acids and they're like in micro

360
00:16:03,330 --> 00:16:02,090
molar concentrations but those possibly

361
00:16:05,470 --> 00:16:03,340
arose from serpent anization

362
00:16:07,750 --> 00:16:05,480
photosynthesis we have no idea at this

363
00:16:09,580 --> 00:16:07,760
point but compared to like an organic

364
00:16:11,710 --> 00:16:09,590
rich system you can support a lot more

365
00:16:15,820 --> 00:16:11,720
diversity just because you have a lot

366
00:16:17,530 --> 00:16:15,830
more energy so at our low pH wells that

367
00:16:20,020 --> 00:16:17,540
are less stressful to the microorganisms

368
00:16:22,090 --> 00:16:20,030
there's not many electron donors that we

369
00:16:24,370 --> 00:16:22,100
know of that are in those fluids to

370
00:16:25,990 --> 00:16:24,380
support life and so there are some

371
00:16:28,060 --> 00:16:26,000
organic molecules so there's some

372
00:16:29,830 --> 00:16:28,070
heterotrophic organisms there's possibly

373
00:16:33,370 --> 00:16:29,840
hydrogen that's just being drawn down

374
00:16:37,300 --> 00:16:33,380
but there actually isn't much to support

375
00:16:40,180 --> 00:16:37,310
life there it's freshwater so you would

376
00:16:43,000 --> 00:16:40,190
expect an even greater diversity on the

377
00:16:50,110 --> 00:16:43,010
scale of all life looking at anything