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Planetary Habitability in and outside the Solar System
Robin WordsworthHBS Workshop on the
Business and Economics of Space11/4/2017
Robin WordsworthHBS Workshop on the
Business and Economics of Space11/4/2017
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…
Wordsworth, Ann Rev EPS, 2016Data and images from: 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?
R = 0.23p < 0.001
R = −0.0033p = 0.93
Wordsworth et al., JGR, 2015
WARMSCENARIO RAINFALL
COLDSCENARIO SNOWFALL
ORBITER OBSERVATIONS
MODEL / DATA INTERCOMPARISONS
GLOBAL VALLEY NETWORK MAPHynek et al. 2010
Wordsworth, Ann Rev EPS, 2016
Our ‘icy highlands’ hypothesis for the early martian climate
Bursts of methane and hydrogen may have warmed Mars in the past
http://photojournal.jpl.nasa.gov/catalog/PIA16834
Wordsworth & Pierrehumbert 2013, ScienceWordsworth et al. 2017, GRL
Curiosity rover drill core Etiope et al., Icarus, 2013
Bursts of methane and hydrogen may have warmed Mars in the past
http://photojournal.jpl.nasa.gov/catalog/PIA16834
Curiosity rover drill core Etiope et al., Icarus, 2013
ESA Trace Gas Orbiter:
Mars 2020 Landing Site Selection
NE Syrtis
Gusev CraterJezero Crater
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‐1system
Exoplanets: Is there life on other worlds?
Gliese 1132b:(discovered last year by Harvard CfA team)
Berta‐Thompson et al. 2016, Nature
TRAPPIST‐1system
Observational techniques
https://palereddot.org/696‐2/http://nexsci.caltech.edu/workshop/2012/talks/HeatherKnutson_124.pdf
TRANSIT SPECTROSCOPY HIGH‐DISPERSION DOPPLER SPECTROSCOPY
Snellen et al., 2010
How do we look for life remotely?
CO2 + H2O + hν CH2O + O2
Holland, 2006
Earth’s oxygen atmosphere is created by life! But O2 can also be produced abiotically…
Wordsworth & Pierrehumbert (2014)
Tian & Ida (2015); Luger & Barnes (2016)
LOW ATMOSPHERIC NITROGEN
HIGH EARLY LUMINOSITY (RED DWARF STARS)
Models of exoplanet atmosphere evolutionATMOSPHERIC CIRCULATION PHOTOCHEMISTRY
ATMOSPHERIC ESCAPE TO SPACE
OUTGASSING FROM INTERIOR
Atmospheric Predictions
Schaefer et al., ApJ, 2016Wordsworth 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.
http://time.com/4003903/best‐cassini‐saturn‐photos/
• 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?