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[Music]

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hi guys I'm not as well dressed or as

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poetic as the previous guy but uh we'll

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see what I can do all right so I'm

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Jonathan you can call me Johnny

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I'm from Imperial College and today I'm

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going to talk about to talk to you about

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lipids on Mars so there are two very

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important questions that I want to try

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and answer during the course of this

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talk firstly can we understand the

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processes of preservation of bio markers

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in Martian environments and two how can

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we use that to tell us more about and

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inform us about future life detection

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missions on Mars and to do that I'm

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going to talk about biomarkers

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appropriate terrestrial analogs and how

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they work together to give us an idea of

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the preservation potential of these

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environments so first thing we need to

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ask ourselves is what are we looking for

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because there's no point spending a

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million dollars billions of dollars on a

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rover to send to Mars and we don't know

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what we want to find so the answer there

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is of course biomarkers which Bradley

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has kindly told us and the definition of

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which is here but the question is what

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makes a use of biomarker Y how do we

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learn to choose what biomarker we want

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so for example let's say that you want

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to find out more about dinosaurs okay

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what biomarker to use for dinosaurs and

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the answer that is bones and there are

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two reasons there are two reasons why

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you use bones as a biomarker of

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dinosaurs the first one is that they're

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highly resistant to degradation

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dinosaurs died millions of years ago and

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you can still find bones in pristine

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conditions today the second thing is

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that bones are highly diagnostic of

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different types of dinosaurs for example

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if you see the plates of a Stegosaurus

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then you know that they're from a

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Stegosaurus and not from a t-rex for

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example so similarly when we look at

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microbial mats on Mars which is why we

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think I would have been the most evolved

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life on Mars we look at lipids so you

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guys already know what lipids are

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because Bradley told you what they were

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but essentially they are fatty acids we

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have a variety of functions in the cell

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such as triglycerides as energy stores

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glycol lipids as signalers and perhaps

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most importantly phospholipids as the

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components of some membranes which means

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that as

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long as your organism had a cell

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membrane it will have lipids so similar

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to bones lipids the hydrocarbon

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derivatives of lipids are highly

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resistant to degradation and lipids can

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be diagnostic indicators of different

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biosynthetic pathways or of different

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domains of life so now that we figured

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out what we want to look for we need to

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figure out where to look for them and in

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order to do that we need to identify

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what the most common rock types that

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were deposited in various p major

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periods of Martian history and we look

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at that through the mineralogical errors

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the fellow seein that the ekayon and the

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city rican and we can further constrain

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where we look for these rocks by

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figuring out where there is evidence for

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liquid water now the question is how do

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we understand the processes that are

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occurring in the environments millions

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and millions of miles away and we do

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this by using terrestrial analogs which

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are locations on earth that are assumed

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to mimic some if not all of the

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environmental conditions of Mars such as

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geological biological chemical and the

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reason why we do this is well we can't

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get Martian rocks just yet there's no

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sample return missions and with Trump in

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charge there may never be so instead we

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look closer to earth we try understand

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processes occurring on earth and then

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extrapolate that to Mars and so for

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example the fill ocean which comprises

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mostly of iron-rich clays they are

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derived from the weathering of mafic

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bath salts we use glazed oils or

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volcanic clastic sediments as simulants

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for this environment similarly when we

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look at the vehicle which is mostly jera

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sites which is an iron surface salt

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because the Deccan had a lot of sulfur

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outgassing we look at acid mine drainage

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or sulfur stream so for example this is

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one of the classical terrestrial

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analogues Rio Tinto in Spain and finally

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in the city region where there is mostly

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very high dry and other anhydrous ferric

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oxide we look at iron bogs and fens now

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these are still a lot of variety of

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environments so today I'm going to focus

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on my work in the thean environment and

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this particular terrestrial analogue so

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let's take a closer look at that so this

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is a this is a picture of my study area

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there is a guy here for size for scale

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geologists very careful about scales so

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what what let's take a look low so like

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I want to

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Oh screaming so this is a self esteem

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self esteems are caused by the

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dissolution of sulfides usually it is

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pyrite into water and what happens is

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that that this eventually deposits jera

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sites which an iron sulfate salt and is

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very similar to terror to environments

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formed on Mars such as in Meridiani

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Planum

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now as you can see very clearly these

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environments are capable of supporting

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extremely for the organisms ecosystems

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of these extremophiles organisms and

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these are very useful to us because if

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these environments can support extrema

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philic organism earth then these same

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invariants may have been able to sport

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similar organisms on Mars and if we can

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find out how what these organisms look

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like and how they are preserved in Earth

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rocks then we can figure out what they

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would look like if they had been on Mars

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and are preserved in Mars rocks so once

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again this is where my study area is of

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course the best analogues for Mars are

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found the south coast of England we like

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most other selfish streams this surface

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stream is derived from pyrite in the

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wheeldin beds in the surroundings

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geology and like Mariana Planum the

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primary meteorology is jarosite but

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there's also good light which is an iron

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oxide derived from the transmission of

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this jarosite

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under humid conditions also present of

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course is the ever-present Clay's now

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the organic inputs into this environment

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include acidophilic algae microbial mats

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which are primarily purple sulfur

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bacteria as well as like netic wood and

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what we try to investigate is how the

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lipids from these organic inputs are

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preserved in rocks in these sulfur rich

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environments so this is how we do it

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firstly we collect a bunch of samples we

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took nine different course in order to

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sample the lateral and vertical

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variations in the stream we then

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separate them by mineralogy send them

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for XRD analysis powder them so that we

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can prepare them for blind eye

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extraction which is a type of liquid

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liquid extraction technique that will

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remove the lipids from these samples we

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then derivatives them and put them on a

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gas chromatography mass spectrometer aka

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the GCMs now before I show you the gist

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this GCMs data let's take a look at what

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a core profile would look like in this

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soft stream so at the very top you have

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your microbial mat beneath that you have

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a gut layer that slow transitions into

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jarosite and the very bottom you have

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clays so this is the GCMs data where

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3m represents a microbial mat sample 3r

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represents a gunite sample and 3c

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represents a clay sample now not many of

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you may know how to interpret GCMs data

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so what is what you're showing here is

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the GC data each of these Peaks

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represents a different organic molecule

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in this case a different lipid species

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and you can identify that lipid species

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by looking at the mass spectrometer part

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the data the MS part of data the height

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of those Peaks represents the relative

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abundance of that particular lipid

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species to a different to all the other

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Peaks and we usually use an internal

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standard in this case the is to help

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give us a Quantic quantification of how

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much lipid there is in this sample so

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what do we want to find out from this

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GCMs data well obviously you want to

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figure out what lipids are being

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preserved secondly we want to figure out

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there any patterns in lipid preservation

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that would be able to distinguish them

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from abiotic sources or you then want to

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figure out if what these biomarkers can

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tell us about the organisms living in

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these environments and lastly we want to

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figure out if there's a preservation

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bias are some lipids better preserved

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than others and while the factors that

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affect them so before I go into the raw

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data etc let's take you let's remember

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what the different types of lipids are

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so these are saturated lipids they don't

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have any functional groups other than

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the carboxyl group at the end and the

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other fatty acids they are named

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depending on what functional group we

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have for example a double bond an extra

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methyl group or a hydroxyl group so this

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is the GCMs data except with colors this

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time you have abundance on the y-axis

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the different lipid species on the

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x-axis and each of those colored boxes

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represents a different group or

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different family of lipids now the one

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thing that should stick out to you is

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that there seem to be a lot larger

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abundance and diversity of lipids in the

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Gotha layer as compared to the clay

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layer now for geologists that seems

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really weird because clays are generally

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bought associated with the preservation

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of organic molecules then for example an

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iron oxide as you can see the clays only

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possess c16 and c18 saturated fatty

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acids so I'll talk about that later but

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another thing I would like to point out

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to you is what we call an even overall

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predominance in the carbon chain lengths

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of the saturated fatty acids so

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c14 c16 and c18 carbon are much higher

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in abundance than c 15 and C 17 carbons

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and this makes sense because this is a

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configuration that's very preferred by

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terrestrial organisms but what this

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means that this is a Biogen pattern

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right you can't form this kind of

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pattern abiotic lis so this is a pattern

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that would be good for distinguishing

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between biotic and abiotic signals so

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next let's take a look at what these

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biomark can tell us about the organisms

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that lived in these environments so we

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can split them into two there are

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general and specific biological

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indicators a general biology indicator

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is something that is indicative of life

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in general and usually these are the

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most well preserves and they should be

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ubiquitous in all samples and in this

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case it would be c16 and c18 saturated

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fatty acids because as you can saw as

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you saw they were found in all samples

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including clays and this makes sense

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because they're the most common

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saturated fatty acids in all of

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organisms the only thing is that these

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don't provide a lot of texts on my data

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so we look to specific biological

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00:09:59,580 --> 00:09:57,610
markers to tell us that and we can use

278
00:10:01,650 --> 00:09:59,590
these to figure out whether or not

279
00:10:05,820 --> 00:10:01,660
something was an anaerobe an Arab a

280
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bacteria or archaea now some of these

281
00:10:09,510 --> 00:10:07,810
are not super useful for example we

282
00:10:12,270 --> 00:10:09,520
don't think that life on Mars would have

283
00:10:14,430 --> 00:10:12,280
developed aerobic metabolism or plants

284
00:10:15,870 --> 00:10:14,440
so we can cross those out but the rest

285
00:10:18,290 --> 00:10:15,880
of them are still very relevant in case

286
00:10:21,000 --> 00:10:18,300
we find any organic signals on Mars

287
00:10:22,470 --> 00:10:21,010
unfortunately one thing you need to

288
00:10:25,190 --> 00:10:22,480
notice is that most of these are

289
00:10:27,150 --> 00:10:25,200
functional functionalized lipids and

290
00:10:28,710 --> 00:10:27,160
what usually happens is that

291
00:10:30,270 --> 00:10:28,720
functionalize lipids aren't very well

292
00:10:32,940 --> 00:10:30,280
preserved so this is the relative degree

293
00:10:35,010 --> 00:10:32,950
of preservation on the y-axis over the

294
00:10:36,900 --> 00:10:35,020
lipid diversity on the x-axis and you

295
00:10:38,730 --> 00:10:36,910
can see that so these are the

296
00:10:40,620 --> 00:10:38,740
functionalize lipids and you can see

297
00:10:42,330 --> 00:10:40,630
that the relative degree of preservation

298
00:10:44,640 --> 00:10:42,340
is much lower for these lipids as

299
00:10:46,800 --> 00:10:44,650
compared to the saturated fatty acids so

300
00:10:49,200 --> 00:10:46,810
although functionalize lipids are very

301
00:10:51,360 --> 00:10:49,210
good at telling us taxonomy information

302
00:10:53,400 --> 00:10:51,370
about the organisms that live in these

303
00:10:55,680 --> 00:10:53,410
environments they may not be very well

304
00:10:58,530 --> 00:10:55,690
preserved or Martian on Martian

305
00:10:59,940 --> 00:10:58,540
environments right so this is the

306
00:11:01,740 --> 00:10:59,950
preservation bias that we need to take

307
00:11:04,050 --> 00:11:01,750
an account off when we look at Mars

308
00:11:06,960 --> 00:11:04,060
so what other what other things could

309
00:11:07,769 --> 00:11:06,970
affect this preservation bias well there

310
00:11:09,869 --> 00:11:07,779
appears to be a min

311
00:11:12,509 --> 00:11:09,879
gobias as we saw because goethite

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00:11:14,730 --> 00:11:12,519
possessed more fatty acids then did the

313
00:11:16,530 --> 00:11:14,740
Clay's and that's really unusual so

314
00:11:18,179 --> 00:11:16,540
there could be a number of reasons for

315
00:11:19,860 --> 00:11:18,189
this right the gunfight contains more

316
00:11:22,949 --> 00:11:19,870
abundance and a higher diversity of

317
00:11:24,360 --> 00:11:22,959
lipids but the implication of this is

318
00:11:26,460 --> 00:11:24,370
that organic material could be

319
00:11:29,429 --> 00:11:26,470
sequestered in what we call a rusty sink

320
00:11:30,989 --> 00:11:29,439
these are the organic molecules could be

321
00:11:33,329 --> 00:11:30,999
attached to these ions and they could be

322
00:11:35,759 --> 00:11:33,339
buried and this is mimics a terrestrial

323
00:11:37,769 --> 00:11:35,769
phenomenon where up to 21% of organic

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00:11:40,259 --> 00:11:37,779
carbon in terrestrial segments is bound

325
00:11:41,730 --> 00:11:40,269
to iron phases and so the implication of

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00:11:44,009 --> 00:11:41,740
this and this is the one thing that you

327
00:11:45,780 --> 00:11:44,019
take away from this talk is that goodbye

328
00:11:49,170 --> 00:11:45,790
and other iron oxides could you have

329
00:11:50,519 --> 00:11:49,180
astrobiological portance on Mars so one

330
00:11:53,040 --> 00:11:50,529
more thing before I wrap at the top as

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you can obviously see these lipids were

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00:11:56,970 --> 00:11:54,970
found in an extant community they were

333
00:11:58,439 --> 00:11:56,980
being produced in real time we need to

334
00:12:00,749 --> 00:11:58,449
find out what these lipids look like

335
00:12:03,629 --> 00:12:00,759
three to four billion years later right

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because Mars Mars life likely existed

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only 3 4 billion years ago so the

338
00:12:08,850 --> 00:12:06,999
primary process that me to look out for

339
00:12:11,100 --> 00:12:08,860
is what we call deep carboxylation and

340
00:12:12,509 --> 00:12:11,110
this is a very simplified explanation of

341
00:12:14,850 --> 00:12:12,519
what it is but essentially what happens

342
00:12:17,970 --> 00:12:14,860
is that your saturated fatty acids

343
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become alkanes by losing a co2 group and

344
00:12:21,360 --> 00:12:20,110
if you remember the even overawed

345
00:12:23,460 --> 00:12:21,370
predominance pattern that I talked about

346
00:12:25,290 --> 00:12:23,470
in the fatty acids well because you're

347
00:12:27,329 --> 00:12:25,300
losing a single carbon atom what happens

348
00:12:29,689 --> 00:12:27,339
is that this predominance becomes an

349
00:12:32,670 --> 00:12:29,699
over even predominance in alkanes and

350
00:12:35,610 --> 00:12:32,680
remember the general biological markers

351
00:12:41,220 --> 00:12:35,620
well they become from c16 and c18 fatty

352
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acids C 15 and C 17 alkanes so let's go

353
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over the conclusions let's return to the

354
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two questions that we asked themself at

355
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the very beginning of this lecture what

356
00:12:51,329 --> 00:12:49,269
are the processes of preservation of

357
00:12:53,999 --> 00:12:51,339
Mars and can we understand them answers

358
00:12:56,040 --> 00:12:54,009
yeah we can because we can use lipids as

359
00:12:58,530 --> 00:12:56,050
biomarkers we can select appropriate

360
00:13:00,869 --> 00:12:58,540
terrestrial analogs in this case sulfur

361
00:13:02,970 --> 00:13:00,879
streams for Tek and Mars we know that

362
00:13:04,559 --> 00:13:02,980
certain species of lipids can be used

363
00:13:06,030 --> 00:13:04,569
for as diagnostic indicators for

364
00:13:08,210 --> 00:13:06,040
different metabolisms or different

365
00:13:10,350 --> 00:13:08,220
domains of life but that these are

366
00:13:12,179 --> 00:13:10,360
affected by the preservation of these

367
00:13:13,889 --> 00:13:12,189
species depending on what species they

368
00:13:15,990 --> 00:13:13,899
are and what mineralogy is present in

369
00:13:17,790 --> 00:13:16,000
the analogue environment so how do we

370
00:13:20,940 --> 00:13:17,800
use this to figure out more about future

371
00:13:22,290 --> 00:13:20,950
missions to Mars well we know that we

372
00:13:23,700 --> 00:13:22,300
figured out that good fights and other

373
00:13:25,500 --> 00:13:23,710
iron oxides are possibly of

374
00:13:27,360 --> 00:13:25,510
astrobiological importance and we've

375
00:13:30,630 --> 00:13:27,370
identified several potential biogenic

376
00:13:33,360 --> 00:13:30,640
sanctions such as c16 and c18 saturated

377
00:13:36,030 --> 00:13:33,370
fatty acids as well as you pee or eel or

378
00:13:39,510 --> 00:13:36,040
sorry yo p or OAP patterns in fatty

379
00:13:59,010 --> 00:13:39,520
acids and alkanes respectively and thank

380
00:14:02,190 --> 00:13:59,020
you the n hi um for a given organism or

381
00:14:05,370 --> 00:14:02,200
organism group how many up to how many

382
00:14:06,930 --> 00:14:05,380
different lipids signatures can result

383
00:14:09,050 --> 00:14:06,940
is a strictly one-to-one or could it be

384
00:14:13,560 --> 00:14:09,060
many - well it could be many - one um

385
00:14:15,300 --> 00:14:13,570
mostly because basically many organisms

386
00:14:17,160 --> 00:14:15,310
organisms basically produce a large

387
00:14:18,450 --> 00:14:17,170
amount of lipids and this the lipids

388
00:14:20,130 --> 00:14:18,460
I've shown you are only a small fraction

389
00:14:21,690 --> 00:14:20,140
of that of that number there are many

390
00:14:22,770 --> 00:14:21,700
many other different types of little bio

391
00:14:24,360 --> 00:14:22,780
signatures that could be present

392
00:14:26,670 --> 00:14:24,370
depending on the type of organism and

393
00:14:28,710 --> 00:14:26,680
it's usually quite difficult to to

394
00:14:30,390 --> 00:14:28,720
pinpoint a specific lipid to a specific

395
00:14:32,100 --> 00:14:30,400
organism which is why sometimes you just

396
00:14:33,900 --> 00:14:32,110
have lipids that correspond to entire

397
00:14:36,270 --> 00:14:33,910
domains of life like for example certain

398
00:14:38,100 --> 00:14:36,280
but aspin lipid could say this is formed

399
00:14:43,620 --> 00:14:38,110
by bacteria but we have no idea what

400
00:14:45,120 --> 00:14:43,630
bacteria it is um in your preservation

401
00:14:48,450 --> 00:14:45,130
um

402
00:14:50,820 --> 00:14:48,460
slide your palmitic acid seem to be a

403
00:14:53,070 --> 00:14:50,830
lot less preserved than the stearic acid

404
00:14:55,260 --> 00:14:53,080
yeah it's just interesting that is it

405
00:14:56,820 --> 00:14:55,270
they're not very that they're very

406
00:14:57,990 --> 00:14:56,830
structurally similar and all yeah even

407
00:15:00,150 --> 00:14:58,000
that those are the two that show up the

408
00:15:01,530 --> 00:15:00,160
most that is that's quite an unusual and

409
00:15:04,170 --> 00:15:01,540
unusual pattern that we had I observed

410
00:15:07,410 --> 00:15:04,180
I'm still not very sure why that was the

411
00:15:09,090 --> 00:15:07,420
case because c16 and c18 obviously

412
00:15:12,690 --> 00:15:09,100
permit against es is obviously the

413
00:15:14,370 --> 00:15:12,700
highest most abundant of those of the of

414
00:15:16,650 --> 00:15:14,380
the saturated fat is all fatty acids in

415
00:15:18,720 --> 00:15:16,660
general so it was quite unusual that we

416
00:15:21,270 --> 00:15:18,730
saw this particular pattern and we're

417
00:15:22,830 --> 00:15:21,280
still not sure what caused it if you

418
00:15:24,390 --> 00:15:22,840
have any ideas like I would love to hear

419
00:15:25,830 --> 00:15:24,400
them yeah I mean just structurally I

420
00:15:26,970 --> 00:15:25,840
can't think of it especially they are

421
00:15:28,110 --> 00:15:26,980
pretty much the same all that's

422
00:15:30,150 --> 00:15:28,120
happening is that you have an additional

423
00:15:32,580 --> 00:15:30,160
methyl group at the end right sorry I -

424
00:15:33,980 --> 00:15:32,590
the two methyl groups at the end so by

425
00:15:35,720 --> 00:15:33,990
right that shouldn't be any

426
00:15:53,490 --> 00:15:35,730
friends in terms of preservation but we

427
00:15:57,220 --> 00:15:55,690
so in a few months MSL is going to

428
00:16:00,160 --> 00:15:57,230
arrive at hematite Ridge in Gale Crater

429
00:16:01,960 --> 00:16:00,170
if we see kite as part of that Ridge how

430
00:16:03,580 --> 00:16:01,970
do you think they should sample it how

431
00:16:07,830 --> 00:16:03,590
do i think they should sample it well I

432
00:16:10,630 --> 00:16:07,840
hope they don't blow it up yeah well

433
00:16:12,130 --> 00:16:10,640
that's not that's so that's so one of

434
00:16:15,430 --> 00:16:12,140
there was another thing about biomarkers

435
00:16:16,780 --> 00:16:15,440
that that was a that's a key point

436
00:16:19,000 --> 00:16:16,790
biomarkers that I didn't explain and

437
00:16:20,680 --> 00:16:19,010
that is that they should be easily and

438
00:16:23,350 --> 00:16:20,690
analyzed in the a geochemical

439
00:16:26,710 --> 00:16:23,360
environment and one of the problems is

440
00:16:28,510 --> 00:16:26,720
the way that we analyze biomarkers on

441
00:16:30,790 --> 00:16:28,520
Mars is that we tend to blow them up

442
00:16:33,190 --> 00:16:30,800
because we use thumper thermal thermal

443
00:16:34,780 --> 00:16:33,200
pyrolysis and that's actually quite a

444
00:16:36,520 --> 00:16:34,790
large problem of Mars it's the reason

445
00:16:37,660 --> 00:16:36,530
why we can't sample much of massive

446
00:16:39,790 --> 00:16:37,670
surface because of the presence of

447
00:16:42,370 --> 00:16:39,800
perchlorates or other oxidants on the

448
00:16:44,050 --> 00:16:42,380
surface because what happens is when you

449
00:16:45,970 --> 00:16:44,060
have a strong oxidant and you have

450
00:16:49,030 --> 00:16:45,980
hydrocarbons and you put them together

451
00:16:51,550 --> 00:16:49,040
and you burn them combustion occurs and

452
00:16:53,230 --> 00:16:51,560
you lose all your signals so that's

453
00:16:55,750 --> 00:16:53,240
another that's a very big problem which

454
00:16:58,120 --> 00:16:55,760
obviously I would I would like for that

455
00:17:00,310 --> 00:16:58,130
to be wet chemistry to do it but that

456
00:17:08,140 --> 00:17:00,320
may or may not be possible because bring

457
00:17:10,069 --> 00:17:08,150
solvents over to Mars etc etc all right