How to Search for Life in the Solar System
Morgan L. Cable, Damhnait Gleeson, Abby Allwood, Steve Vance, Britney Schmidt, Ty Robinson and David J. Des Marais Astrobiology Webinar 16 January 2014
Where do we look for life?
Earth Analogue: Hydrothermal Vents
Europa •
Ice shell
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Hydrated minerals, SO2 on surface
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Utilize redox chemistry to thrive
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Subsurface liquid water ocean
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Possible hydrothermal activity
Micro and macromolecular flora, fauna
Where do we look for life?
Earth Analogue: Atacama Desert, Chile
Mars •
Warm, wet past
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Reasonable temperature regime
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Low water activity
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Halophiles (high salinity tolerant)
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Bacterial spores
Where do we look for life?
Titan • • • • •
Thick (1.5 bar) atmosphere Water-ice surface coated in organics Subsurface liquid water ocean Hydrocarbon lakes at the poles Huge inventory of organic molecules
Earth Analogue: Pitch Lake (Trinidad and Tobago) •
Hydrocarbon-metabolizing bacteria
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Poly-extremophiles
Where do we look for life?
Earth Analogue: Antarctica
Enceladus •
Icy crust
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Subsurface liquid water ocean
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Subglacial ecosystems
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Geysers in south pole
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Psychrophilic, halophilic organisms
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Some higher life forms
Platforms to search for life •
Remote observation – Look at the planet from orbit, or using a telescope – Benefits: Large surface area, can study global effects – Drawbacks: Poor resolution (compared to in situ), low limits of detection
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In situ detection – Use a lander, rover, or other robotic explorer (or humans) – Benefits: Good resolution and limits of detection (depending on technique) – Drawbacks: Limited sample scope, issue of contamination
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Sample return – Get a sample, bring it back to Earth for analysis – Benefits: Can use ultrasensitive techniques not available for space flight – Drawbacks: Prohibitively expensive, sample preservation, issue of contamination
Platforms to search for life
Remote sensing •
Imaging spectroscopy – Uses sunlight as light source, measures surface reflectance – Usually UV to near-IR, sometimes thermal IR – Relevance for life: Can detect the ‘red edge’ of chlorophyll, water, and the signatures of gases (methane) and minerals
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Gamma-ray spectroscopy – Measures the gamma ray distribution emitted from a surface (usually due to bombardment by cosmic rays) – Relevance for life: Can map the elemental and isotopic distribution of the entire surface of airless bodies (Europa, Enceladus, etc.)
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Radar – Measures reflectance of radio frequencies (typically) – Relevance for life: Can be used to look for water
In situ detection •
Microscopy – Can image samples down to micron or even sub-micron level (depending on optics) – Can use various excitation sources to capture fluorescence – Relevance for life: Identification of microfossils (stromatolites), bacterial cells
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Molecular analyses (GC-MS, HPLC) – Separates species in the gas or liquid phase (based on size, charge, interaction w/substrate) – Detection via mass spectrometry, conductivity, etc. – Relevance for life: Identification of specific molecules (amino acids, ATP, sugars), isotope ratios
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Immunoassays – Targets specific molecules using antibodies – Microfluidics-based techniques could do real-time PCR – Relevance for life: Can detect specific proteins and other biomarkers, chiral discrimination
Challenges to in situ life detection •
Detection in soil/regolith – Poor extraction efficiencies – Reactivity induced upon adding water (i.e., perchlorates)
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Organic analysis on Titan – Tholins (simulated Titan aerosols) change once they are warmed up to room temperature, or exposed to liquid water – How do we analyze the sample without chemically altering it?
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Radiation on Europa – On the surface, a human would get a lethal dose of radiation in minutes – Need to protect reagents in addition to electronics
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Sample collection on Enceladus – How do we get a plume sample without destroying it?
Looking to the future •
We need to fly new life detection technologies – “Failure is not an option” is the wrong strategy here
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Take advantage of low cost, high risk opportunities – CubeSats, NanoSats
Thank you!
