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hi everyone thanks for tuning in to my

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talk today

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my name is denise buckner i'm a phd

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student at the university of florida

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and today i'll be presenting some of my

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research on the assessment of electron

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beam radiation as a lipid

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decontamination technique for light

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detection instruments

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as an overview first i'll discuss lipid

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biomarkers and their application for

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life detection

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then i'll introduce my group's novel

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life detection instrument the extractor

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for chemical analysis of lipid

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biomarkers in regolith or excalibur

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then i'll discuss the importance of

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decontamination and introduce electron

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beam of radiation as a potential

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solution

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then i'll explain the experiments we

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conducted and the results

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as a preview we found that the technique

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was not effective at removing lipid

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contaminants of interest

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finally i'll discuss my next steps and

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future research

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in the search for extraterrestrial life

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lipid biomarkers are organics of special

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interest

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lipids are universal to all life as we

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know it primarily for building membranes

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that protect and segregate biological

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materials from the external environment

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cellular life requires encapsulation and

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amphiphilic fatty acids are the organic

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molecules that fulfill this structural

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role

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lipids can form both biotically and

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abiotically and have been detected

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throughout the solar system

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particularly in carbonaceous meteorites

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delivered to earth and mars throughout

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both planets histories

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for reference fatty acids make up over

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sixty percent of the soluble organics

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found in carbonaceous meteorites

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additionally small simple hydrocarbons

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and chlorinated molecules have been

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detected on mars by the sample analysis

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of mars instrument onboard the curiosity

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rover

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but further exploration is needed to

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better understand what lipids could

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exist on mars

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and what the source of those lipids

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could be

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lipid sphere origin diagnostic molecular

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features and patterns

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mean that the confirmation of individual

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molecules and patterns and distributions

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of lipids within a sample

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can indicate whether those compounds

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were synthesized biotically or

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abiotically

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a potential key to detecting

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extraterrestrial life

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lipids are also recalcitrant and robust

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molecules that can persist for billions

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of years in the terrestrial geologic

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record

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which is orders of magnitude longer than

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other biomarkers like dna

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proteins and amino acid and antiomeric

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excess

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if life arose on mars during its most

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habitable epochs about 3 billion years

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ago

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lipid biomarkers could represent some of

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the only remaining molecular evidence of

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that life preserved there today

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to search for lipid biomarkers on mars

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and beyond we are building the extractor

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for chemical analysis of lipid

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biomarkers in regolith or excalibur

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this instrument will replicate and

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automate what chemistry lipid extraction

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and analysis techniques

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that have been successfully used in

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terrestrial laboratories for over 70

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years

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streamlining and scaling them for

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this image shows excalibur's sample

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processing steps

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first excalibur will accept a 50 gram

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regulator ice sample

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then convince or crush the sample to

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reduce particle size

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at this point any volatile organics will

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be cold trapped and sent to an evolved

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gas analyzer

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back to the sample lipids will then be

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extracted from the regolith via

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agitation and organic solvents

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and the mineral residue filtered out

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leaving behind a mixture of pure lipids

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suspended in solvent

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the resulting lipid extract will then be

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concentrated 2500 times to improve

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signal

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then sent to a suite of coupled

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analytical instruments for detailed

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molecular characterization

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these could include a gas chromatograph

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mass spectrometer or gcms

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a thermochemolysis gcms or a laser

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desorption ionization mass spectrometer

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however if excalibur is to effectively

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detect lipids decontamination is

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essential

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lipid biomarkers are abundant on earth

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but may be low in abundance in an

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extraterrestrial sample

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since excalibur will concentrate the

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lipid extract 2500 times

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any terrestrial lipids that end up in

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the aliquot will also become

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concentrated

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and sent to the analytical instruments

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those instruments coupling to excalibur

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have ultra low limits of detection

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with picota femtomole sensitivities so

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even trace amounts of contamination

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could present a significant problem

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further compounding the issue recent

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studies on contamination in spacecraft

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assembly clean rooms

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show that up to 10 to the fifth viable

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cells per square meter

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add up to 10 to the eighth total cells

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per square meter remain on hardware

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surfaces post cleaning

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this translates to roughly 500 picomoles

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of fatty acid

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per square meter finally traditional

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decontamination techniques approved by

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nasa for planetary protection purposes

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leveraged in clean rooms or applied in

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organic chemistry laboratories

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are either ineffective at sufficiently

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removing lipid contaminants

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or are effective at removing lipid

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contaminants but are incompatible with

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sensitive materials

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used to construct excalibur and other

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life detection instruments

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to address this issue we investigated

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electron nemo radiation as a potential

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solution

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electron fema radiation is a technique

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that's widely used for sterilization and

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decontamination

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in food medical device and wastewater

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treatment industries

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and is sometimes used to sterilize

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spacecraft for planetary protection

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compliance

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but has not been applied to life

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detection hardware in particular

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electron fema radiation works by

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generating and focusing a stream of high

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energy electrons onto materials

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undergoing sterilization

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decontamination is achieved in less than

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60 seconds

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the beam delivers tunable controlled

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doses that can penetrate up to 10

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centimeters through cardboard glass and

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other packaging materials

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potentially reaching trapped or

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encapsulated contaminants

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these electrons can kill microbes and

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destroy some organics via radiolysis

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through direct hits to molecules and by

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generating radicals

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but effects on molecular lipid

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contaminants had not previously been

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investigated

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so the goal of our study was to test

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this technique as a final

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decontamination step

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that could be applied to the assembled

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excalibur instrument

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the intention was to enhance but not

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replace traditional

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cleaning for example the figure on the

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right shows how electron beam of

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radiation could factor into the

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excalibur cleaning plan

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first heat tolerant components would be

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baked to the highest allowable

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temperatures

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then throughout assembly the instrument

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would be frequently flushed with

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solvents to remove any introduced

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contaminants

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these same solvents could also be used

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to pre-clean components that were unable

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to be baked

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finally once the assembly of the

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instrument is complete excalibur could

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then undergo a radiation to destroy

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any residual lipids

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so for this study we first selected five

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target lipids to test

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shown on the left including a saturated

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and unsaturated fatty acid

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and n-alkane cholesterol and cholesterol

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these molecules were selected for their

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astrobiological relevance and

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contamination potential

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we took our selected lipids and

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deposited them individually into glass

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vials and sealed them each under high

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purity nitrogen

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we then sent the lipid samples to

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undergo a radiation at stereotech

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sterilization facility

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at doses of either zero kilograms 50

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kilograms or 100 kilograms

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following a radiation we use gcms to

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analyze the lipids

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quantify breakdown and identify

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radiolytic products

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we expected that the five lipids would

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be effectively degraded following

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treatment

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but we actually observed no substantial

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reduction in the standards

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this graph illustrates the abundance of

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each lipid relative to starting

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concentration

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after 500 kilograms and 100 kilograms of

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radiation

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you can see that the concentration is

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close to 100 for all five of the lipids

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at each dose

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which indicates that no significant

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degradation occurred

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the pink line representing palmitic acid

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shows that lipid abundance for this

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compound

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decreased to approximately 79 following

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100 kilograms of irradiation

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but no corresponding reduction was

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observed for the palmitic acid samples

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that were irradiated at 50 kilograms

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likewise the green line representing

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cholesterol

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shows that the abundance for this

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compound decreased to approximately 84

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following a radiation at 50 kilograms

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but no corresponding reduction

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was observed for the cholesterol samples

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that were radiated at 100 kilograms

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so we conclude that none of our five

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standards are consistently or

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substantially degraded

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however while we observe no substantial

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reduction in overall lipid abundance

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numerous minor breakdown products were

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identified in the irradiated samples

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so some degradation or transformation is

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occurring

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radiolytic products include shorter or

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smaller molecules and recombinants

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in these two example chromatograms from

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the saturated and unsaturated fatty

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acids that were radiated at 100

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kilograms each

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we identified a homologous series of

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fatty acids and hydrocarbons

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of every chain length shorter than the

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parent compound these represent

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breakdown products that were either

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decarboxylated

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or cleaved at various points in the

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hydrocarbon tail

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we also identified recombinants which

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include some of the molecules

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illustrated here

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like the unsaturated fatty acid with one

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double bond that was formed after the

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saturated fatty acid

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with no double bonds was irradiated we

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also see short dicarboxylic acids and

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oxoaccidents

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which could represent fragments of two

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fatty acids that were cleaved and then

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combined together

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we also observe a pheron which appears

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to have formed via cyclization of the

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hydrocarbon tail around the carboxyland

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so what does this mean according to our

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results the 50 and 100 kilogram doses

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applied to the five lipid standards

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did not sufficiently destroy or remove

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the molecules under our experimental

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perimeters

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but some breakdown is apparent much

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higher doses could potentially be more

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effective at destroying lipid

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contaminants

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but those doses could also damage or

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degrade instrument hardware

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so we don't recommend using electron

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beam radiation as a lipid

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decontamination technique for excalibur

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or other lipid-based life detection

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instruments however the resilience of

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the lipids could suggest that these

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organics are a bit more resistant to

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radiation-induced degradation than we

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had initially expected

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this is astrobiologically relevant

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because understanding lipid degradation

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rates in planetary

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environments where surface radiation is

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higher than on earth

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is key for informing where and how deep

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to dig when searching for minimally

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altered lipids

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the results are especially relevant to

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europa a body that experiences high

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levels of electron radiation

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sourced from jupiter's magnetosphere to

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follow up on this research we're

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focusing on two sets of tasks

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first we're continuing to look for

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cleaning methods that can sufficiently

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remove lipid molecules

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without damaging excalibur hardware

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these include thermal

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chemical and laser-based methods second

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we hope to further explore the effects

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of radiation on lipid lifetimes

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in support of future life detection

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missions to mars and europa

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these analyses will include experiments

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that apply geologically relevant

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doses and types of radiation to analog

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samples made up of simulated martian

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regolith or european ice

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spiked with lipids so that lifetimes can

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be quantified and breakdown products

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predicted

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so finally i'd like to thank nasa ames

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research center for funding this project

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with the center innovation funds grant

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blue marble space institute of science

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for supporting me during my research

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the north dakota space grant consortium

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for providing you with research

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fellowship

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and the university of north dakota's

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department of space studies for

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facilitating my work

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so thanks again everybody for listening

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to my talk