Earths and super-Earths Science Enabled by Direct Imaging Technology Renyu Hu, Ph.D. Jet Propulsion Laboratory California Institute of Technology Workshop on Technology for Direct Detec4on and Characteriza4on of Exoplanets April 9, 2018 Pasadena CA
Earths and super-Earths Science Enabled by Direct Imaging Technology Renyu Hu, Ph.D. Jet Propulsion Laboratory California Institute of Technology WorkshoponTechnologyforDirectDetec4onandCharacteriza4onofExoplanetsApril 9, 2018 Pasadena CA
CommonalityofSmallPlanetsExoplanet Demography
2
Earth
Neptune
Jupiter
Transit RadialVelocity
Imaging Microlensing
DetectableviatransitH2 Atmospheres
4
HAT-P-11b, a Neptune-sized planet
100 120 140 160 180 200 220 240 260 280 300 320Equ. Temp [K]
0
2
4
6
8
10
12
14
Obs
Inde
x of
HST
Obs
Inde
x of
JW
ST /
2.7
HST Observable
JWST Observable
PH-2 bLHS-1140 b
K2-18 b
K2-3 dK2-9 b
K-16 bK-167 e
TRA-1 h (2)
TRA-1 e (3)
TRA-1 f (4)
TRA-1 g (6)
TRA-1 d (12)
Complica4onwithstellarvariabilityNon-H2 Atmospheres?
5 Rackham et al. 2018
TransitFeature- Upto10%forH2
atmospheres- <1%fornon-H2
atmospheres
EmissionFeature- 1-2%
StarshadeRendezvousMissionsimulatedimageofanearbystarDirect Detection of a Solar System
6 Seager et al. 2015
EXO-SFinalReport2015
Howdoweknowwhetheranexoplanethasanatmosphere?whetheranexoplanet’satmospherehasevolved?whetheranexoplanethasgeological/biologicalacDviDes?
9
Spectralfeaturesofrockyplanetarysurfaces
wavelength wavelength
Refle
c4vity
Refle
c4vity
Detect Rocky Exoplanet Surfaces
10
Directdetec4onofrockyexoplanets
Detect Rocky Exoplanet Surfaces
Huetal.2012
Metal-richPrimarycrustwithmantlerippedoff
UltramaficPrimarycrustwithmantleoverturnor
secondarycrustfromhotlavasFeldspathic
PrimarycrustwithoutmantleoverturnBasal4c
SecondarycrustGranitoid
Ter4arycrustClay
AqueouslyalteredcrustIce-richsilicate
Ice-richsurfaceFe-oxidized
Oxida4veweathering
11
WhatwelearnedfromDSCOVRobserva4onsofEarth
Rotation Period and Hydrological Cycle
Jiangetal.2018
Minimumsamplingrateis10hours
13
Howdoweknowwhetheranexoplanethasanatmosphere?whetheranexoplanet’satmospherehasevolved?whetheranexoplanethasgeological/biologicalacDviDes?
14
ImportanceofClouds
Detecting an Earth-like Atmosphere
16
H2O
500 600 700 800 900 1000Wavelength [nm]
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35Al
bedo
No CloudCumulus CloudCirrus CloudMean
Diverseatmosphericcomposi4onofrockyplanets
Detecting Earths and Super-Earths
17Gaillard&Scaillet2014
H2O
0.1 0.2 0.5 1 2 5 1000.10.20.30.40.50.60.70.80.9
1
XC/XO
X H
Water-richAtmosphere
Oxygen-richAtmosphere
Chemically as Gas Giant Atmospheres
Hydrocarbon-rich Atmosphere
H2, CO,CH4, CO2,H2O
CO,CO2
Depend on Temperature
DiversityofAtmospheres
Continuum from Super-Earths to Sub-Neptunes
18 Hu & Seager 2014
H2 – Rich
H2 – Poor
Carbon – Poor
Carbon – Rich
InreflectedlightDistinguish Water Worlds vs. Giant Planets
20Hu 2014; Filippatos & Hu in prep.
InterplaybetweencloudsandC,N,Oabundances
HazeProduc4oninPhotochemicalProcesses
NeptunesandH2O-richSuper-Earths
SpectralDegeneraciesandInforma4onContent
500 550 600 650 700 750 800 850 900 950 10000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Wavelength [nm]
Geom
etric
Albe
do
H2−Dominated Atmosphere, Cloud Deck at 0.4 BarsH2−Dominated Atmosphere, Cloud Deck at 2 BarsH2O−Dominated Atmosphere, Cloud Deck < 10−3 Bars
CH4
CH4
CH4
CH4
CH4
CH4
CH4
CH4CH4
CH4 H2O
H2O
H2O
NH3
Howdoweknowwhetheranexoplanethasanatmosphere?whetheranexoplanet’satmospherehasevolved?whetheranexoplanethasgeological/biologicalacDviDes?
21
The image part with relationship ID rId2 was not found in
JWST/WFIRST/Otherspacetelescopes
Planetary Spectrum
Atmospheric Composition
Surface Source flux
Radiative Transfer
Atmosphere Chemistry
TowardsCharacterizingRockyExoplanets’Atmospheres
22
VolcanicemissioncontrolsO2buildupinCO2atmospheresCharacterize Rocky Exoplanets’ Atmospheres
10−14 10−12 10−10 10−8 10−6 10−4 10−2 100
10−1
100
101
102
103
104
105
Mixing Ratio
O2
OO3
Pres
sure
[Pa]
Hu et al. 2012
Solid:Earth-likevol.emissionDashed:Lowvol.emissionDoged:Novol.emission
23
Escapeofhydrogenisbalancedbyanetoxidizingfluxfromtheatmospheretotheocean
O2andCH4togetherasabiosignatureCharacterize Rocky Exoplanets’ Atmospheres
Domagal-Goldman et al. 2014 24
MeasuringvolcanicoutgassingCharacterize Rocky Exoplanets’ Atmospheres
25
0.1 0.2 0.3 0.5 1 2 30
0.1
0.2
0.3
0.4
0.5
0.6
Wavelength [microns]
Refle
ctivit
y
N2 AtmospheredP = 0.1 µm
S8 Aerosol ReflectionS8 Absorption
Earth X 3000Earth X 1000Earth X 100
Earth X 10Earth X 1
0.1 0.2 0.5 1 2 5 10 20 50 1000
0.2
0.4
0.6
0.8
1
Wavelength [microns]
Tran
smiss
ion
N2 AtmospheredP = 0.1 µm
S8 Aerosols
Earth X 1
Earth X 10
Earth X 100
Earth X 3000Earth X 1000 H2SO4
AerosolsCO2
CO2
SO2H2SH2OSO2
5 8 10 20 30 50 80 100180
200
220
240
260
280
300
Wavelength [microns]
Brigh
tnes
s Tem
pera
ture
[K] H2SH2OH2O CO2
SO2
SO2
SO2
CH4
N2 AtmospheredP = 0.1 µm
Hu et al. 2013
Transit- Ground-basedtransitsurveys,TESS- JamesWebbSpaceTelescope
(JWST,launch2018)
Directimaging- StarshadeRendez-vouswithWFIRST- Flagshipconceptsfor2020
AstrophysicsDecadalSurvey(HabEx+LUVOIR)
§ Direct imaging will enable characterization of Earths and super-Earths
§ We may learn about: surface type, atmospheric H2O, O2, CO2, rotation period, variability of clouds
§ It may be hard to directly measure: size of planet, mass of atmosphere, liquid water ocean
§ Intrinsic widths of spectral features will determine the required resolution, and the need to measure variability will determine the required collection area
Conclusion
Sensi4vitytoatmosphericsurfacepressureCharacterize Rocky Exoplanets’ Atmospheres
James & Hu, in prep.
Oxygenbuilduppeaksat~1bar
28
10-1 100 101
Surface Pressure [Bar]
10-10
10-8
10-6
10-4
10-2
100
Colu
mn
Mixi
ng R
atio
H2 O2 O3 CO CH4
Tre’ShundaJamesInternatJPL
HowdoesO2buildupdependonsurfacepressureandirradia4on?
SynergybetweentransitanddirectimagingAtmospheres of Wide-Separation Exoplanets
29
Transitspectrumofa229-day-periodexoplanetKepler16-b(HSTGO14927,PIRenyuHu)