Mars Rover Uses Spectroscopy to Detect Diverse Organic-Mineral Associations in Jezero Crater

A new study published in the journal Nature reveals exciting findings from the Perseverance rover's exploration of Jezero crater on Mars. Lead authors Sunanda Sharma and Ryan D. Roppel from the Jet Propulsion Laboratory at the California Institute of Technology report the detection of diverse organic-mineral associations in the Máaz and Séítah formations within the crater floor sequences, revealing the extent and persistence of organic matter on the Martian surface (1).

crater on planet Mars, landscape scene on the red planet | Image Credit: © dottedyeti - stock.adobe.com

The chosen landing site of the Perseverance rover within Jezero crater combines high potential for a location where life could have potentially existed in the past with a diverse array of minerals, including carbonates, clays, and sulfates. The researchers observed interesting formations within the crater floor: Máaz and Séítah, which were investigated in the mission's first campaign. The compositions of these formations, rich in pyroxene, plagioclase, and olivine-bearing cumulate, provide promising conditions for preserving organic materials and potential biosignatures.

The Máaz and Séítah formations are located within the crater floor of the Martian Jezero crater. The Jezero crater is of scientific interest as it was once an ancient lake basin and holds potential evidence of past habitability. The Máaz formation, characterized by a highly cratered and mafic composition rich in pyroxene and plagioclase, is thought to be relatively younger compared to the underlying Séítah formation. Séítah, an older formation, contains rocks that represent an ultramafic olivine-bearing cumulate, rich in magnesium and iron (1). These formations within Jezero crater provide a diverse geological context for studying organic-mineral associations and the potential preservation of organic materials and biosignatures, contributing to our understanding of Mars' history and the potential for life on the planet.

The presence of preserved organic matter on Mars offers valuable insights into the planet's carbon cycle and its potential to support life. While previous studies have detected organic molecules in Martian meteorites at the Gale crater, the current research focuses on the Jezero crater. The team utilized Raman and fluorescence spectroscopy to identify aromatic organic molecules and their specific associations with minerals within the Máaz and Séítah formations. These associations suggest different fates for carbon across different environments, indicating the diversity of aromatic molecules present on the Martian surface.

The research team employed the SHERLOC instrument, a deep ultraviolet (DUV) Raman and fluorescence spectrometer, to analyze the distribution of organic molecules and minerals on rock surfaces within the crater. SHERLOC's unique capabilities allowed for simultaneous measurement of weak Raman scattering and strong fluorescence emission, revealing a range of fluorescence signals consistent with small aromatic compounds. These signals were detected on all ten observed targets and were grouped based on their distinct spectral features (1).

DUV Raman and fluorescence spectrometers utilize specialized instrumentation and techniques in order to detect organic molecules in Martian soil. The spectrometer's deep UV excitation source enables the selective enhancement of Raman scattering and fluorescence emission signals from organic molecules. By matching the excitation wavelength to the electronic transitions of target chromophores, the DUV spectrometer enhances the weak Raman scattering signals, allowing for their detection and analysis. Additionally, the spectrometer's ability to simultaneously measure both Raman scattering and fluorescence emission signals provides complementary information about the presence and characteristics of organic molecules. This technique, coupled with high-resolution spatial mapping capabilities, enables the identification and distribution analysis of organic molecules in Martian soil, contributing to our understanding of the potential for past or present life on Mars.

The findings suggest a diversity of aromatic molecules persisting on the Martian surface, even under harsh environmental conditions. Notably, the identified organic molecules were predominantly associated with minerals linked to aqueous processes, indicating the potential role of these processes in organic synthesis, transport, or preservation on Mars (1).

The detection of diverse organic-mineral associations in the Jezero crater opens new possibilities for studying the Martian carbon cycle, discovery of the potential history of organic material on Mars, and the potential for evidence of present life. Furthermore, these findings contribute to the ongoing Mars Sample Return campaign, as the identified rock cores associated with organic molecules may be used for future detailed analysis on Earth.

The Perseverance rover continues to explore and collect samples, enhancing our understanding of Mars and providing valuable insights into its geological and astrobiological history. The discoveries from spectroscopic studies of the Jezero crater demonstrate the scientific significance of this mission and pave the way for further investigations into the potential habitability of Mars and the existence of organic molecules beyond Earth.

Reference

(1) Sharma, S.; Roppel, R. D.; Murphy, A. E.; et al. Diverse organic-mineral associations in Jezero crater, Mars. Nature 2023, ASAP. DOI: 10.1038/s41586-023-06143-z