In Situ Detection of Organics on Mars

Transcription

1 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

2 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

3 Intensity Intensity SAM measurements of organic volatiles from sample Gas chromatograph Gas release trap sniff Oven Mass spectrometer 1. Evolved gas analysis (EGA) Gas chromatography mass spectrometry (GCMS) Bulk gas evolution x Molecular separation and identification 10 Sample temperature in oven 0 GC retention time

4 Relative abundance What happens to a sample when its heated under helium? thermal desorption pyrolysis

5 Relative abundance What happens to a sample when its heated thermal desorption under helium? O2 pyrolysis O2 release from minerals leads to combustion of gas phase organics and CO2 release

6 Macromolecules Killops and Killops, 1993

7 Relative abundance Character of SAM background in Evolved Gas Analysis (EGA) CO 2 C 4 H 8 CH 4 Higher confidence that organic signals are indigenous to sample m/z and scaling factor The transition is dependent on sample chemistry

8 Relative abundance Rocknest Eigenbrod High temperature release from refractory organic matter CH 4 C3-4 alkyl Rocknest Eolian Drift - Gale Crater floor - scoop site, first analysis by SAM Eigenbrode et al, 2014 AGU Fall Meeting Eigenbrode et al., in prep NASA/JPL-Caltech/MSS

9 Wt. % Chemical composition of Gale, Meridiani and Gusev soils are basaltic and nearly identical in APXS measurements Global signature Composition suggests limited chemical weathering (Berger et al., 2013, JGR) Chemical components Yen et al., 2013, LPSC #2495; Blake et al. 2013, Science.

10 Sheepbed Mbr. Mudstones Murray fm. MSL Team s stratigraphy column (Grotzinger et al, 2015) Pahrump Hills/Marias Pass Confidence Hills Mojave2 Telegraph Peak Buckskin Yellowknife Bay Cumberland John Klein

11 Point Lake Gillespie Lake Sheepbed mudstone John Klein Cumberland Chlorinated C1-C4 chains and benzene detected Yellowknife Bay - Gale Crater floor sediments - drill sites analyzed by SAM - lake deposit (Grotzinger et al., 2015, Science) Freissinet et al., 2015, JGR NASA/JPL-Caltech/MSS

12 SAM EGA of Cumberland Single-Ring Aromatic Hydrocarbons m/z and scaling factor CH 2 CH 3 O CH 2 CH 2 Relatively weak signals Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

13 SAM EGA of Cumberland C1-C4 Alkyl Hydrocarbons m/z and scaling factor C1 Example carbon chain C2 C3 C4 Relatively weak signals Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

14 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

15 Buckskin Telegraph Peak Confidence Hills Mojave 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) NASA/JPL-Caltech/MSS

16 Relative counts per second SAM EGA of Mojave2 m/z and scaling factor C1 C1-C5? Alkyl Hydrocarbons C2 Example carbon chain C3 C4 C5? Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

17 Relative counts per second SAM EGA of Mojave2 Single-Ring Aromatic Hydrocarbons m/z and Scaling factor Cl CH 2 CH 3 O CH 2 CH 2 Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

18 Relative counts per second SAM EGA of Mojave2 Organic sulfur volatiles Methanthiol Dimethylsulfide Thiophene Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

19 MS Response (cps x 1000) Relative MS Response Identification of Organic Sulfur Compounds by SAM GCMS of Mojave Retention Time (seconds) s s MJ2 CB_Blank2

20 Comparison to Martian meteorites Example: Tissint

21 Lab EGA analysis of Tissint martian meteorite m/z and scaling factor C1 C1-C4 Alkyl Hydrocarbons Single-Ring Aromatic Hydrocarbons Organic sulfur volatiles O C2 C3 CH 2 C4 Thiophene CH 2 CH 2 Similar high temp release and composition as in situ Mars signals Eigenbrode et al, AGU, 2015 Eigenbrode et al., in prep

22 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.

23 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

24 Questions?