Unveiling the nitrogen chemistry of Titan with the Dragonfly Mass Spectrometer

Titan offers a window to an extremely complex and abundant organic chemistry, initiated in its high atmosphere by solar radiation and energetic particles from Saturn’s magnetosphere, and which sediments and triggers chain reactions down to the surface. The final products are solid organic aerosols present in high concentration in the atmosphere and at the surface of Titan.

Remote sensing and in situ analyses of the atmosphere, composed primarily of N₂ and CH₄, have indicated that nitrogen is incorporated in significant amount in both the gaseous and solid phases [1]. Laboratory experiments simulating Titan’s atmospheric chemistry have yielded a wide variety of organic molecules based on C, N and H atoms [2], including pre-biotically important nitrogen-bearing molecules such as amines [3], nucleobases and possibly amino acids [4]. Once deposited at the surface, the solid organic materials may be exposed to geophysical conditions that promote chemical evolution beyond the atmospherically generated population. Notably, in certain regions organics may have been exposed to transient liquid water, such as in putative cryovolcanic regions or impact craters [5]

 

One major goal of the Dragonfly mission is to measure Titan surface materials found in sites that are representative of different environments such as dunes and icy surfaces. Chemical analyses of these different materials by the Dragonfly Mass Spectrometer (DraMS) will be performed with Laser Desorption/ionization Mass Spectrometry (LDMS) and Gas Chromatography Mass Spectrometry (GCMS). These two complementary analytical techniques combine to allow detection and identification of compounds with a wide range of mass and chemical functionalities. This dual approach is soon to be demonstrated in situ with the Mars Organic Molecule Analyzer (MOMA) experiment on the Rosalind Franklin martian rover [6]. However, as the nature of the samples and molecules to be analyzed significantly differs between Mars and Titan surface, the sample measurement approaches and the preparation techniques have to be optimized to the detection and identification of Titan’s organic molecules. We present here the LDMS and GCMS techniques that will be used to analyze in situ materials collected at Titan’s surface. We demonstrate the detection of chemical compounds of interest to prebiotic chemistry, with an emphasize on the amines and amides chemical families as well as nucelobases, such molecules being of high interest for prebiotic chemistry given their ubiquity in biochemical systems and possible role in red-ox energy pathways. We also present analyses of laboratory analog materials that represent Titan’s complex organics.