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[Music]

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[Applause]

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good afternoon everyone i'm andrew

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Shumway I'm a graduate researcher at the

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University of Washington I'm working

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there with Professor Jonathan toner

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studying the formation and stability of

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Bryon's as they exist on the surface of

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Mars I'm here today to present some

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results about from some experimental

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work that we've done looking at how

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brian's may exist under more extreme

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conditions than previously thought

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possible

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in fact my results likely indicate that

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under certain conditions brian's may

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exist throughout the entire year and in

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the most extreme conditions on mars

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making them effectively unfeasible so

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trans transient or perpetually liquid

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water on the surface of Mars even in

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relatively small quantities it has deep

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Astra biological significance water is

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the cornerstone in our search for

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habitable environments beyond Earth and

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there are many hazards on Mars that

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potential organisms would face including

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low temperature low pressures high

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exposure to radiation but I think

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perhaps none are as difficult to

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overcome as the lack of water so life on

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Earth can thrive in some of these most

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extreme environments but all life as we

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know it needs water to survive so if

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there are microorganisms on Mars that we

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should be able to identify their source

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of water and even if there are no

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microorganisms alive on Mars today

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soon we will be bringing our own life to

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the planet humans and for potential

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future missions and missions to Mars

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humans are gonna require water and

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likely the first missions will bring

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their own water but this is inefficient

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because water is very heavy and

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expensive to transport so a much better

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it would be much more sustainable to

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find a source of water there on Mars

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that we could use so for these reasons

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characterizing water on Mars is critical

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in defining both present and future

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habitability of the planet and it's

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central to our mission as

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astrobiologists this presents a

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challenge though because when we look at

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the surface of Mars today we find a very

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cold and dry place it's not an ideal

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environment for life to exist and while

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there's past evidence that liquid water

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existed the water that is there or that

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if we look at the phase diagram of water

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and the range of Martian service

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conditions we can see that any pure h2o

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would exist only as a solid ice or as a

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water vapor gas but the surface of Mars

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is rich in salts which reduces the

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evaporation rate and can allow water to

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exist under these extreme conditions so

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a great deal of work has already been

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done to characterize Martian brian's

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like these brands made from Mars salts

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can have extremely low freezing points

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down to negative 74 degrees Celsius in

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the case of calcium perchlorate another

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way that water is predicted to exist on

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Mars is as adsorbed brines or as

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adsorbed water what's happening here is

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that water vapor will adhere to surfaces

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in this case soil this adhesion is just

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driven by Van der Waals forces which are

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weak electromagnetic interactions but

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neither of these previously studied

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systems tells the whole story

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realistically any brines that likely

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exists on Mars are within the soil so

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it's essential to understand the

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properties of soil brien mixtures soil

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and salt and water what distinguishes

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our expand experiment from these

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previously studied systems is that we

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investigate samples of soil and brine

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and find that they do not behave

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identically to either of these

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previously studied systems so the goal

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in this experiment is to answer the

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question under what conditions can Mars

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akan brines exist in Martian soils this

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comes in two steps the first is to study

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how brian's form the soil by taking up

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water from the atmosphere and we did

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this by measuring the water activity if

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you are not familiar with water activity

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essentially it is a measure of the the

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effective concentration of water or how

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much water is available for chemical and

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biological interactions next we looked

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at brine stability to identify phase

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transitions such as freezing salt

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precipitation and glass formation and

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soil brian mixtures this phase diagram

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shows the phases for pure magnesium

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perchlorate brian as a function of

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concentration and temperature

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and we find that soils cause Bryan's to

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deviate strongly from this picture in

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order to investigate these two themes we

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created soil Brian samples that are

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analogous to what we expect to find on

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Mars so we've never had a return mission

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from Mars so we don't have any real Mars

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soil to work with so we have the next

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best thing

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Mars soil simulant which is essentially

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just crushed weathered basaltic mimics

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the composition of Martian soil and for

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our salt we chose magnesium perchlorate

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we chose that this because the wet

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chemistry experiments on the Phoenix

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lander found approximately 0.6 weight

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percent per chlorate

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in Martian soil at its landing site so

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when you put it all together you get

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soil Brian sample that looks something

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like this and using these soil Brian

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mixtures our first task was to measure

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the water activity as a function of

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Brian salt concentration the way that we

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did this is we have our soil Brian

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sample of an unknown water activity and

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we introduce it to a reference material

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for which the water activity is known

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both of these materials are put into an

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evacuated chamber and held at a constant

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temperature and water vapor is allowed

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is able to exchange between the two

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samples until equilibrium is reached at

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that point we can compare the mass

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before and after equilibration and

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calculate the water activity so the

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water activities for both of the

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materials would be identical so

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calculating the water activity and the

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brian concentration so here are the

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results from that but first actually i

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want to show you this is what for the

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pure magnesium perchlorate solution

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would look like for water activity as a

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function of salt concentration you can

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see that water activity is lower at

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higher salt concentrations this is

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because at these higher concentrations

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more of the water is interacting with

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assault so less of it is available to be

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used in other processes here in black

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are the data for a mixture of martian

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soil simulant and magnesium perchlorate

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Brian the concentration of salt in this

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experiment was one weight percent that's

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because it's very similar to the what

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was detected by the Phoenix lander we

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also studied soil Brian mixtures

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higher salt concentrations so you can

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see here in orange is to weight percent

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and in red 5 weight percent and as we

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get higher and higher concentrations it

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approaches the trend for the pure brine

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so this has really big implications for

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the way that we study Mars relevant

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brian's the lower water activity means

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that brian's absorbed onto soil are less

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available to chemical and biological

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processes further to address the

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question of stability and when these

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brian's actually remain liquid this drop

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and water activity should correspond to

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depressed freezing point temperatures

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meaning that the brian's will be more

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stable than previously thought and we

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can confirm this by measuring the phase

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transitions directly using a

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differential scanning calorimeter DSC is

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it what it does is it identify his phase

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transitions by measuring the heat flow

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anytime that a phase transition occurs

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there will be a characteristic

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absorption or release of heat and the

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DSC measures those changes so here's the

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heat flow through one sample of one

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weight percent soil brine mixture and an

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activity of 0.91 the sample was cooled

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down to negative 150 degrees Celsius and

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this plot shows you the change in heat

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as we slowly warm it up towards zero at

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this point here the heat flow drops

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suddenly melting ice is an endothermic

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process meaning that it absorbs heat so

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and that's exactly what we're seeing

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here we see similar features at lower

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water activities 0.8 0.73 but when we

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get to really really low water

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activities below 0.5 this feature

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disappears entirely it doesn't appear so

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what this says is that water it never

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freezes in these samples even though it

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we lowered the temperature to negative

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150 degrees Celsius so let's go back to

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this figure which compares a pure brine

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with a one weight percent magnesium

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perchlorate Brian soil mixture like I

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mentioned before this decrease in water

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activity caused by the soil does in fact

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correspond to a decrease in freezing

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temperature the depression of the

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freezing point is so strong then in

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samples below 0.5

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water activity the Bryan's never freeze

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and this is what we deem unfreeze

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suitable water because in these dry

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Martian conditions such Bryan's will

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remain liquid over the full range of

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Mars's temperatures as I wrap up I'd

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like to leave you with just a few

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closing thoughts Brian's on Mars will

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likely exist as adsorbed phases onto

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soil and they will remain liquid at much

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lower temperatures than pure brines this

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expands the range of conditions where

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liquid water is stable and allows it to

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be available in some of the most extreme

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and conditions on the planet adsorbed

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brian's could serve as a potential

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source of water for microbes on mars but

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it would be an extremely hostile

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environment because of these very very

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low water activities that we're

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measuring and so this project has only

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just scratched the surface of this

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there's plenty of more future work to do

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many more salts to investigate many

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different types of soils that we can use

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clays as well so that's the direction

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that I'd like to go in the future with

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this project but to wrap up I'd just

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like to think like my sponsors and my

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home department and I'll take any

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you know we have time for a few

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questions

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hi Herman Martinez from the University

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of Michigan a very interesting

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presentation thank you very much for

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that I was wondering about the Mars

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analog soil that you that you'd used

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where did you get it from exactly or

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have you do you have details on that one

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yes you can actually buy it online it's

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that uh it is Mars Mojave simulant I

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bought this one name in soil it's

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Martian Gardens

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namely Mojave yes yes thank you very

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much Alex Paul of NASA gloried so when

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you did this experiment when you put

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both soil perchlorate and another

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solution with no one activity together

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how big are those samples whenever you

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put with what you try to equilibrate so

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the soil sample is about half a gram yes

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they're they're pretty small okay

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because concern was whenever I do

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experiments with quarries is that you

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can form like a crust

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you know whenever you know a particular

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pressure so it can be deceptiveness but

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you know at Papa Graham it's probably

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not the fact mm-hmm Jennifer Hanley low

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observatory can you explain again how

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you determine the activity water in your

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soil plus salt plus water one got it

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from the water plus salt one can just

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explain like made me go back to that

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slide and explain again please sure I

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don't want to go too far back but

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there's there's an equation to calculate

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it so we weighed the sample before

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calibration and after collaboration so

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we can know precisely how much water is

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in each sample and from that amount of

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water you can back out the brine

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concentration and use that to calculate

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water so your how's the water getting in

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there it's exchanged through water

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vapour okay okay

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David Stillman's very similar kind of

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question how much water do you have in

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this one weight percent sample like did

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you start with a known amount or a

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because yeah are you daily

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singing it in and then waiting and then

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making the water activity measurement

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sure so we start with perfectly dry soil

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we dehydrate it and treat it with a

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magnesium solution and then add we

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pipette in magnesium perchlorate brine

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and then allowed to equilibrate at a

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water activity all right and I've won -

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and I'm gonna pile on top of that but

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yeah and I get your process but it's all

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based on the mass balance

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have you taken into account that

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sorption

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because if you start from a perfectly

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dry so you're gonna probably adds up a

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significant amount of water and you have

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only one weight percent of perchlorate

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so it's really small so if you want to

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make sure that you really estimate

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properly the amount of water that goes

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in the liquid phase of the back row each

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enemy to make the same mass balance on

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the dry salt without a fly right yes we

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have done knowledge not include the

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results in this in this presentation

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yeah we did we did the same experiment

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without perchlorates just a soil sample

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to see the effect of adsorption when I

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salts do we have any other question no

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did those freeze if it was just absorb

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water cuz I would expect it wouldn't

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freeze we did not put those through the

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DSC okay yeah so we didn't measure the

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phase transitions but that's a very good

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interesting feature all right so let's

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think again our speaker for the money