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Planetary Habitability in and Outside the Solar System

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Planetary Habitability in and Outside the Solar System Planetary Habitability in and outside the Solar System Robin Wordsworth HBS Workshop on the Business and Economics of Space 11/4/2017 Talk Outline • Mars climate and habitability research – The Faint Young Sun Paradox – Mars 2020 Rover Landing Site Selection • Exoplanet research – How do exoplanet atmospheres evolve? – Is remote life detection possible? • Thoughts on the intersection between fundamental science and space exploitation Abundant liquid water flowed on Mars in the past… Data and images from: Wordsworth, Ann Rev EPS, 2016 Tanaka (1987), Williams et al. (2013), Malin & Edgett (2003), Howard et al. (2005), Head & Pratt (2001) …but the climate should have been very cold! • The young Sun was 25% fainter than it is today • Our models show that under these conditions, early Mars should have been cold enough to freeze out CO2 onto the surface • How could Mars have possibly sustained habitable conditions? ORBITER OBSERVATIONS GLOBAL VALLEY NETWORK MAP Hynek et al. 2010 MODEL / DATA R = 0.23 p < 0.001 INTERCOMPARISONS WARM SCENARIO RAINFALL R = −0.0033 p = 0.93 COLD SCENARIO SNOWFALL Wordsworth et al., JGR, 2015 Our ‘icy highlands’ hypothesis for the early martian climate Wordsworth, Ann Rev EPS, 2016 Bursts of methane and hydrogen may have warmed Mars in the past Curiosity rover drill core Etiope et al., Icarus, 2013 Wordsworth & Pierrehumbert 2013, Science http://photojournal.jpl.nasa.gov/catalog/PIA16834 Wordsworth et al. 2017, GRL Bursts of methane and hydrogen may have warmed Mars in the past Curiosity rover drill core Etiope et al., Icarus, 2013 ESA Trace Gas Orbiter: http://photojournal.jpl.nasa.gov/catalog/PIA16834 Mars 2020 Landing Site Selection Jezero Crater Gusev Crater NE Syrtis Mars 2020 Landing Site Selection http://www.americaspace.com/wp‐content/uploads/2015/08/si‐mars_w_v8.jpg Exoplanets: Is there life on other worlds? Gliese 1132b: (discovered last year by Harvard CfA team) TRAPPIST‐1 system Exoplanets: Is there life on other worlds? Gliese 1132b: (discovered last year by Harvard CfA team) Berta‐Thompson et al. 2016, Nature TRAPPIST‐1 system Observational techniques TRANSIT SPECTROSCOPY HIGH‐DISPERSION DOPPLER SPECTROSCOPY https://palereddot.org/696‐2/ Snellen et al., 2010 http://nexsci.caltech.edu/workshop/2012/talks/HeatherKnutson_124.pdf How do we look for life remotely? Earth’s oxygen atmosphere is created by life! But O2 can also be produced abiotically… LOW ATMOSPHERIC NITROGEN CO2 + H2O + hν CH2O + O2 Wordsworth & Pierrehumbert (2014) HIGH EARLY LUMINOSITY (RED DWARF STARS) Holland, 2006 Tian & Ida (2015); Luger & Barnes (2016) Models of exoplanet atmosphere evolution ATMOSPHERIC CIRCULATION PHOTOCHEMISTRY ATMOSPHERIC ESCAPE TO SPACE OUTGASSING FROM INTERIOR Atmospheric Predictions Schaefer et al., ApJ, 2016 Wordsworth et al. submitted, 2017 Atmospheric Predictions Testable by JWST from 2019 onwards! Morley et al., ApJ, 2017 Science Conclusions • Mars was intermittently habitable in the past, and the most viable explanation for this is transient H2/CH4 greenhouse warming of a mainly icy early climate. • Mars 2020 Rover and Trace Gas Orbiter data will help test these ideas further, as well as many other aspects of the planet’s geology, climate and potential for human habitation. Beyond 2020, the future of Mars exploration in the U.S. is uncertain. • Earth‐like exoplanets have been discovered. We are developing models to allow us to search for life on them remotely. The James Webb Space telescope and other large‐scale facilities will be able to detect the atmospheres of these planets and hence directly test model predictions. • Images such as this one, and space science in general, are an important public good • Traditional funding system = small amount of direct taxation, missions by national agencies (e.g. NASA) • In the knowledge economy, are there alternative ways to drive space exploration (citizen science, outreach, philanthropy, ?) that better reflect its true worth to society? http://time.com/4003903/best‐cassini‐saturn‐photos/.
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