Earth and super-Earth Atmospheres

Dimitar Sasselov

Harvard-Smithsonian Center for Astrophysics

&Harvard Origins of Life

Initiative

Outline

1. The ‘generic’ terrestrial planet

2. The ‘mini-Neptune’ problem

3. Characterizing geochemical cycles

The “Tree of super-Earths”S

uper

-Ear

ths

Mini-Neptunes

OceanPlanets /WaterPlanets

TerrestrialPlanets /Dry, RockyPlanets

Fe -richmantle

?H2O -richmantle

?

?

?

?

(Sasselov, 2008, Nantes)

Earth & super-Earthsvs. gas & ice giants

UV / photo-chemistry

surface /phase transition /boundary layer

atmosphereMatm << Mp

mantle

a well-mixedreservoir

fluxesLoss

Plate tectonics on a 1 MEarth Planet:

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

The “Tree of super-Earths”S

uper

-Ear

ths

Mini-Neptunes

OceanPlanets /WaterPlanets

TerrestrialPlanets /Dry, RockyPlanets

Fe -richmantle

?H2O -richmantle

?

?

?

?

(Sasselov, 2008, Nantes)

Super-Earthsvs.

mini-Neptunes

“Confusion region”

How to distinguish mini-Neptune from super-Earth:

(Mil

ler-

Ric

ci, S

eage

r,S

asse

lov

200

9)

How to distinguish mini-Neptune from super-Earth:

< The 3 types of atmospheres

(Miller-Ricci, Seager,Sasselov 2009)

Zoomed

Super-Earths geochemistry,e.g. the Carbonate-silicate cycle, or Sulfur cycle, etc.

Planets of differentinitial conditionscan be “driven” toa set of geochemicalequilibriaby global geo-cyclesover geologicaltimescales.

Dominant Sulfur outgasing: with JWST

Kaltenegger & Sasselov (2009)

SO2 CO2

No O2 or O3 , but N2 , CO2 , & CH4 .

Conclusions

• Understanding the bulk geochemistry of Earth-like1. planets is an achievable goal,• Use super-Earths as good proxies for Earth,• Much preparatory theory work still needed, e.g.:

• Does the Sulfur (SO2) cycle have a stabilizingfeedback;

• What is the full catalog of possible geo-cycles,incl. on water planets (convecting Ice VII mantle);

• Understand scaling of plate tectonics with mass.

The “Tree of super-Earths”S

uper

-Ear

ths

Mini-Neptunes

OceanPlanets /AquaPlanets

TerrestrialPlanets /Dry, RockyPlanets

Fe -richmantle

?H2O -richmantle

?

?

?

?

KeplerLegacy

TESS &JWSTLegacy

ADDITIONAL SLIDES

Interior Structure: Radius & Composition

Valencia, Sasselov, O’Connell (2007)

Pure Iron super-Earths ? - No.

Marcus, Sasselov,Hernquist, & Stewart (2009)

- giant impacts simulations

70% Fe core:only below4-5 MEarth

Water super-Earths vs. Dry

Zeng & Sasselov (2009)

CoRoT-7b

2

3

1

1 105 20

QuickTime™ and a decompressor

are needed to see this picture.

Front-end

Thermal enclosuresof the spectrograph

HARPS-NEF

The 4.2-m WilliamHerschel telescope,Canary Islands

1m/s in 1h for V=12

QuickTime™ and a decompressor

are needed to see this picture.

Front-end

Thermal enclosuresof the spectrograph

HARPS

The 4.2-m WilliamHerschel telescope,Canary Islands

QuickTime™ and a decompressor

are needed to see this picture.

Thermal enclosuresof the spectrograph

HARPS

A laser comb for HARPS-NEFwavelength calibration

Mode-lockedfemtosecond laser:essentially a 10-15s

‘strobe’

• narrow lines • coherent• equally-spaced• intense• spans optical octave

Li e

t al. 2

00

8

nm

Our red astro-comb in the lab.

Comb lines at the telescope - FLWO, 2008