Abstract EANA2026-59

One of the main goals of the Rosalind Franklin mission is the search for biosignatures in the Martian soil and subsurface. This includes the detection of complex organic molecules with the MOMA instrument [1], including laser desorption and ionization mass spectrometry (LDMS) and Gas chromatography mass spectrometry (GCMS). One main issue regarding GCMS is the abundance of perchlorate salts on Mars: The perchlorate ion (ClO4)- emerges oxygen during the initial pyrolysis step which causes combustion of organics to CO2.
This leads to the question of what extent perchlorates affect detection of organic molecules with LDMS. While initial results show that the detection of certain organic compounds remains possible [2], there has been no systematic study looking into the possible effect on detection limits and the influence of different mineral matrices.
Here, we present results from a measurement series with different Mars-relevant mineral matrices such as nontronite, vermiculite, olivine, and magnesite.  These minerals were mixed with different target organics in different concentrations, for instance cholesterol [3], alkanoic acids and one aromatic substance. Magnesium perchlorate (1 wt% which corresponds to the concentration in Martian soil) was added to the samples to compare the limit of detection with and without perchlorate. LDMS spectra were obtained with a Thermo Scientific LTQ XL mass spectrometer in combination with an atmospheric pressure matrix-assisted laser desorption and ionization (AP-MALDI) source with a 266 nm UV laser.
 

References:

[1] Goesmann, F. et al. (2017) Astrobiology 17, 655-684.

[2] Li, X. et al. (2015) Astrobiology 15, 104-110.

[3] Raith, M.C. et al. (2026) Icarus 444, 116829.