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in this talk i'm going to be covering

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some of the work we performed in

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characterizing color peak springs and

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analog environments for the waters of

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for the purpose of this talk we are

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defining an analog environment as a site

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possessing a chemistry approximating

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so in terms of an analog for the surface

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of modern day mars you would expect an

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analog environment to have one of the

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following traits

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it would be sailing

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oxidizing potentially anaerobic or

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microaerophilic and be exposed to high

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levels of ultraviolet radiation

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which of course highlights that an

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analog environment is an analog at a

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specific point in a celestial body's

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history and in a specific location the

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geology of mars is not homogeneous so

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there is variation in chemistry between

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different sites the surface of modern

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day mars is believed to be greatly

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different from the subsurface

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and mars 4 billion years ago is believed

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to be incredibly different and much more

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water-rich than its modern day

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color peak springs is located on axel

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heiberg island which is in the canadian

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high arctic

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it's characterized by polar desert

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conditions meaning it's both very cold

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and very dry and it lies within the

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region of continuous permafrost

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the island is host to a series of

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sulphur rich and saline cold springs

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with some marked on the map shown here

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with either red dots or the gold star

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color peak is incredibly sailing like

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the other springs on the island and

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sulfurous

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but one delineating trait is it is also

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incredibly sulfidic as evidenced from

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the black coloration visible in these

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sediments following from these spring

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source

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this environment was worthy of further

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characterization from the

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microbiological perspective because the

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microbes that survive and are active

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within this environment have previously

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only been partially characterized and

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from the astrobiology perspective this

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environment is argued to be an analog

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when we are considering analog

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environments we first have to ask is it

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chemically and physically relevant

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no environments on earth will be a

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perfect fit but we want it to be as

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relevant as possible

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in terms of the temperatures experienced

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by the color peak springs these fall

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within the range of colder temperatures

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that are modeled in predictions that

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estimate a cold and wet nowakian mars as

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opposed to a warm and white snowakian

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mars

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we then analyze the chemistry of the

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color peak springs

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using icp oes

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shown on the ternary plot we have the

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three most abundant elements calcium

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sulfur and sodium

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and in the bottom right corner

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we have

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here in the red circles

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and the other circles directly on top

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the different chemistries of the color

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peak samples showing that sodium was the

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most abundant elements

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the other markings on this ternary plot

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designates other analog environments on

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earth such as the deccan traps in india

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however some also represent

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modelled martian waters

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for the purpose of this study the

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program chim-xpt was used by dr susanna

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schwentzer

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using as inputs pure water and the

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chemistry of rockness sand collected a

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gale crater by the curiosity rover chim

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xpt estimates what would the chemistry

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of the solution be like if the minerals

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were to dissolve

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and if we go back to this ternary plot

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and we look to the right of the red

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circles and to the left most side of the

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outer red circle we see two diamond

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shapes representing the thermochemically

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modelled waters based on these gale

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crater evaporates

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so at least in terms of the most

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abundant elements the chemistry of the

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waters and sediment of color peak are

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close to the modelled martian water

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the next question in our set of

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experiments was what microbes are

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present in color peak that are

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withstanding this chemical and physical

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regime

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in order to answer this we extracted the

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dna from replicate sediment samples

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using

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a specially tailored dna extraction

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technique to account for the high

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concentrations of salt within the sample

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we then sequenced the 16s rrna gene the

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universal barcode gene that's found in

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all microbes and it gave us the

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the key takeaway from this bar graph is

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the dominance of purple and shades

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thereof

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across these three different bars from

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the replicate sediment samples

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these represent sulfur oxidizing

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bacteria and as is clear from these

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graphs

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sulfur oxidizing bacteria dominates the

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color peak sediment

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so who are the sulfur oxidizers

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sulfur oxidizing microbes are those that

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yield energy through the oxidation of

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reduced sulfur compounds which we know

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to be abundant within the color peak and

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present on the surface of mars and

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within martian meteoritic materials

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sulfide oxidation can occur using oxygen

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as a terminal electron acceptor

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it can also occur in the absence of

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oxygen using nitrate as an alternate

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terminal electron acceptor which is also

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relevant in terms of mars given the

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detection of nitrates within martian

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mudstone samples as reported in the

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sternatile 2015 paper

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many of the sulfur oxidizing bacteria

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that we detected within the color peak

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sediment are also autotrophic organisms

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that convert inorganic carbon in this

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case carbon dioxide to produce organic

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carbon

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in the same way that plants

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they do not need nor can they utilize an

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external source of organic carbon as we

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there is however a slight issue with

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identifying what microbes are present in

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color peak only by looking at dna

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and that is in a cold and saline

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environment

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dna from long dead cells could

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hypothetically persist for millennia

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in order to try and move past this issue

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we also extracted rna from the color

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peak sediment in order to try and look

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at what microbes were more genuinely

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present within this specific environment

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as rna has a much shorter half-life even

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under optimal conditions

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comparing a collapsed dna profile

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to the rna profile

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we see that there is a significant

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reduction in the diversity present

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within the environment

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and we see that there is this continued

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persistence

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both of these sulfur oxidizing bacteria

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represented again in purple

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and of some of the additional diversity

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within the sediment

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but the active microbes

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are still mostly sulfur oxidizing

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the question is then

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independent of the microbiology point of

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view why is this an interesting result

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why is it interesting that microbes with

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this specific metabolism are living and

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thriving in this

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cold pool in the arctic

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and moreover why do we perform any kind

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of characterization of analog

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environments

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and the answer is it enables us to

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generate hypotheses

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we know that a lot of the diversity

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detected within this sediment of this

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self-oxidizing bacteria

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are capable of autotrophy meaning that

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they can fix carbon dioxide as their

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sole carbon source

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combined with how carbon poor the

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sediment is they're most likely

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surviving within this environment

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through the fixation of carbon dioxide

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however as these cells are growing some

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will be leaking either intentionally or

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unintentionally and as some are growing

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they will be dying releasing a pool of

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organic carbon that they themselves

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cannot utilize and we know that there is

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this additional

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package of diversity within the color

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peak sediment

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it is therefore possible that the other

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bacteria within the color peak sediments

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are surviving by growing on the carbon

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produced by the autotrophic sulfur

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oxidizers and this is something shown to

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occur in other environments such as

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hydrothermal vents

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and also in cultivation-based studies

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now in terms of this metabolic process

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we know the concentrations of the

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individual elements that are key for

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sulfur oxidation

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the same is also true

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for martian conditions we know the

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concentrations of nitrates detected

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within the mudstone samples and we know

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the thermochemical composition of the

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waters that were derived from the

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chemistry of the gal crater evaporates

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using gibbs energy equations it's

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possible to deduce whether based on the

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abundance of the elements that are

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required for specific metabolic

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processes whether there would be

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sufficient energy yielded to make this a

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thermodynamically favorable metabolism

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and doing these gibbs energy

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calculations

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only was aerobic and anaerobic sulfur

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oxidation feasible under these proposed

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martian conditions

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they were two of some of the few

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metabolisms that were indeed capable in

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this specific chemical environment

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so how can we take this one step further

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how can we test if the analog community

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is viable in genuine martian chemistries

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moving one step beyond the

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characterization of the proxy

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environments and the modeling of martian

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chemistries

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and we can do this through performing

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simulation experiments

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if we take one step back to the chim

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modeling of the rockness sand chemistry

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and the pure water

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we can use this output to produce a

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liquid medium in which to challenge

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cells

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we can then combine this with two

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different chemically accurate martian

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regolith simulants one based on the

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chemistry of rock nest and one based on

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the more iron iii enriched chemistry of

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hematite slope

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establishing two distinct simulated

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martian chemistries performing this

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under anaerobic conditions in

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combination with the color peak sediment

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to more accurately simulate martian

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conditions

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the question is then is the analog

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community that we're arguing is viable

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under a proxy martian condition

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viable under simulated conditions

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and do we see the persistence of these

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sulfur oxidizing

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bacteria we look at the general

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microbial community again

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and compare this to under rock nest

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conditions we see that the answer is

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indeed yes the purple persists

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indicating that sulfur oxidizers can

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grow under these chemical conditions

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however we do not observe this under the

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iron iii in rich conditions of hematite

289
00:11:36,630 --> 00:11:34,000
slope where the sulfur oxidizers are in

290
00:11:38,630 --> 00:11:36,640
fact eliminated and substituted by these

291
00:11:40,630 --> 00:11:38,640
sulfate-reducing bacteria with the

292
00:11:43,750 --> 00:11:40,640
reasons why requiring further

293
00:11:47,509 --> 00:11:46,069
in conclusion color peak is an

294
00:11:50,069 --> 00:11:47,519
appropriate analogue for mars in the

295
00:11:52,230 --> 00:11:50,079
late nowakian and it's dominated by

296
00:11:54,550 --> 00:11:52,240
sulfur oxidizing bacteria a metabolic

297
00:11:57,110 --> 00:11:54,560
process that is feasible and proposed