In Situ Detection of Organics on Mars

Jennifer Eigenbrode, Andrew Steele, Roger Summons, Amy McAdam, Brad Sutter, Heather Franz, Caroline Freissinet, Maeva Millan, Danny Glavin, Doug Ming, Rafael

Navarro-Gonzales, Pan Conrad, Paul Mahaffy,

the SAM and MSL teams

NAS SSB Search fro Life Across Time and Space

• The SAM instrument and background signals

• In situ detection of refractory organic matter via EGA

• In situ identification of molecules via GCMS

• Comparison to Tissint martian meteorite

SAM measurements of organic volatiles from sample

Gas release trap

Gas chromatograph

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x10

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1000900800700600500400300

GC retention time

2. Gas chromatography mass spectrometry (GCMS)

Inte

nsi

ty

1. Evolved gas analysis (EGA)

Sample temperature in oven

Inte

nsi

ty

Mass spectrometer

Oven

Bulk gas evolution Molecular separation and identification

sniff

What happens to a sample when its heated under helium?

pyrolysis thermal desorption

Rel

ativ

e ab

un

dan

ce

What happens to a sample when its heated under helium?

Rel

ativ

e ab

un

dan

ce O2

pyrolysis

thermal desorption O2 release from

minerals leads to combustion of gas phase organics and CO2 release

Macromolecules

Killops and Killops, 1993

Character of SAM background in Evolved Gas Analysis (EGA)

The transition is dependent on sample chemistry

CO2

CH4

C4H8+

m/z and scaling factor

Higher confidence that organic signals are indigenous to

sample

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e ab

un

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ce

Eigenbrod

Rocknest Eolian Drift - Gale Crater floor - scoop site, first analysis by SAM

High temperature release from refractory organic

matter CH4

C3-4 alkyl

Rocknest

Eigenbrode et al, 2014 AGU Fall Meeting Eigenbrode et al., in prep

NASA/JPL-Caltech/MSSS

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• Global signature

• Composition suggests limited chemical weathering (Berger et al., 2013, JGR)

Chemical composition of Gale, Meridiani and Gusev soils are basaltic and nearly identical in APXS measurements

Yen et al., 2013, LPSC #2495; Blake et al. 2013, Science.

Chemical components

Wt.

%

MSL Team’s stratigraphy column

(Grotzinger et al, 2015)

Pahrump Hills/Marias Pass

Confidence Hills Mojave2 Telegraph Peak Buckskin

Yellowknife Bay

Cumberland John Klein

Mu

rray

fm

. Sh

eep

be

d M

br.

Mu

dst

on

es

Sheepbed mudstone

Gillespie Lake

John Klein Cumberland

Point Lake

NASA/JPL-Caltech/MSSS

Freissinet et al., 2015, JGR

Yellowknife Bay - Gale Crater floor sediments - drill sites analyzed by SAM - lake deposit (Grotzinger et al., 2015, Science)

Chlorinated C1-C4 chains and benzene detected

SAM EGA of Cumberland

m/z and scaling factor

CH2

+

CH3

+

O

+

CH2

+

CH2

+

Single-Ring Aromatic Hydrocarbons

Relatively weak signals

Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

SAM EGA of Cumberland

m/z and scaling factor

C1

C3

C4

C2

Example carbon chain

C1-C4 Alkyl Hydrocarbons

Relatively weak signals

Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

From refractory organic matter to chlorohydrocarbons proposed mechanism: Fenton-like reactions

Ionizing radiation + Organics + Metal catalysts

Low temperature evolution of chloro-hydrocabons may be an indication of radiolytic weathering

Mojave

Confidence Hills

Buckskin Telegraph Peak

NASA/JPL-Caltech/MSSS

Murray Formation at Pahrump Hills - bottom of Lower Mound outcrop at Gale Crater - drill sites analyzed by SAM - lake deposit (Grotzinger et al., 2015, Science)

Example carbon chain

SAM EGA of Mojave2

C1-C5? Alkyl Hydrocarbons

C1

C3

C4

C2

C5?

m/z and scaling factor

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cou

nts

per

sec

on

d

Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

+

Cl

CH2

+

CH3

+

O

+

CH2

+ CH2

+

SAM EGA of Mojave2 Single-Ring Aromatic Hydrocarbons

m/z and Scaling factor

Rel

ativ

e

cou

nts

per

sec

on

d

Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

Thiophene

Dimethylsulfide

Methanthiol

SAM EGA of Mojave2 Organic sulfur volatiles R

elat

ive

co

un

ts p

er s

eco

nd

Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

Identification of Organic Sulfur Compounds by SAM GCMS of Mojave2

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MJ2 CB_Blank2

MS

Res

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cps

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Retention Time (seconds)

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Comparison to Martian meteorites Example: Tissint

Lab EGA analysis of Tissint martian meteorite

C1

C3

C4 Thiophene

C2

m/z and scaling factor

C1-C4 Alkyl Hydrocarbons

Similar high temp release and composition as in situ Mars signals

CH2

+

O

+

CH2

+

CH2

Single-Ring Aromatic Hydrocarbons

Organic sulfur volatiles

Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

Conclusions

• Refractory organic matter is present in the Rocknest eolian sediments and some lacustrine mudstones in Gale Crater

• Possible sources: • Abiotic igneous/hydrothermal?

• Meteoritic?

• Heavily processed biological?

• We don’t know the organic source. Could be a mixture.

Implications

• Organic matter may be widely distributed over the surface and throughout the rock record of Mars

• Supports habitability of the ancient lake environment in Gale Crater ~3.6 billion years ago

Organic molecules = energy and C source for metabolisms

• Supports modern and future habitability

Questions?