False Signs of Life:Abiotic O3 Buildup on

Planets Around M-DwarfsShawn Domagal-Goldman (UW)Ba

ttles

tarG

alac

tica,

200

3

Victoria Meadows Ty Robinson Noe Khafka Mark Claire James Kasting Antigona Segura IGERT/NSF VPL/NAI

Acknowledgements & Collaborators

Spectral model

Chemistry Model

Salary & Computers

Beich

man

, Woo

lf, a

nd L

inde

nsm

ith, 1

999

Beich

man

, Woo

lf, a

nd L

inde

nsm

ith, 1

999

Beich

man

, Woo

lf, a

nd L

inde

nsm

ith, 1

999

Original Question:Are there anoxic biosignatures?

New

Wor

lds O

bser

ver,

2008

Original Question:Are there anoxic biosignatures?

Original Question:Are there anoxic biosignatures?

CH3SHC2H6

CH3SHC2H6

Dom

agal

-Gol

dman

et a

l., in

pre

p.

Original Question:Are there anoxic biosignatures?Yes. But only for planets that orbit M-dwarfs and have high production rates of organic S.

Stumbled Upon Question:Are there ways to make O3 without cyanobacteria?

very

preli

minary

!!

Are there ways to make O3 without cyanobacteria?Are there ways to make without cyanobacteria? Yes.

Dom

agal

-Gol

dman

et a

l., in

pre

p.

How is the O3 madewithout cyanobacteria?

Segu

ra e

t al.,

200

5

How is the O3 madewithout cyanobacteria?

Segu

ra e

t al.,

200

5

O3 + hn O2 + OO3 + hn O2 + O1D

SO2 + hn (SO2)1O2 + hn O + O1D

CO2 + hn CO + O1DCO2 + hn CO + OH2O + hn H + OH

H2CO + hn HCO + HH2CO + hn H2 + CO

SO2 + hn SO + OO2 + hn O + O

Is this signal observable?

C2H6

O3

C2H6

O3

Dom

agal

-Gol

dman

et a

l., in

pre

p.

AD Leo

log (fCH4)

log

(fCO

2)m

ax fO3 (ppb)

Haze

Dom

agal

-Gol

dman

et a

l., in

pre

p.

Is this signal distinguishable?

C2H6

O3

C2H6

O3

Dom

agal

-Gol

dman

et a

l., in

pre

p.

Results/Conclusions This may be something we have to

worry about… but we need to couple the photochemical code to a climate code to verify this result.

Fortunately, the O3 buildup is limited to planets around M-stars… and a haze that is almost certainly detectable.

Future “worry tests”: Planet with lower CO2 levels Planet around a “quieter” M-Dwarf Planet with higher/lower H escape

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