<p>Serpentinization and carbonation have affected ultramafic rocks on Noachian Mars in several places called here serpentinization-carbonation systems (SCS). Among the most prominent SCS revealing mineral assemblages characteristic of serpentinization/carbonation is the Nili Fossae region [1]. Jezero crater &#8211; the target of the Mars 2020 rover &#8211;hosted a paleolake which constitutes a sink for sediments from Nili Fossae [1]. Thanks to the near infrared spectrometer onboard Mars2020 [2], the mission has the potential to offer ground truth measurement for other putative serpentinization/carbonation system documented on Mars. Several important aspects that may be addressed are: Do carbonates result from primary alteration of olivine-rich lithologies or are they derived by reprocessing of previous alteration minerals [3]? What is the composition? and nature of the protolith, which appear to be constituted of considerable amounts of olivine [4]? To reveal critical information regarding the conditions of serpentinization/carbonation, accessory minerals need detailed studies [1; 5]. In case of Jezero Crater, and serpentinization on Mars in general, the main alteration minerals are identified, but little is known about the accessory minerals.</p>
<p>The Nili Fossae-Jezero system has potential analogues in terrestrial serpentinized and carbonated rocks, such as the Leka Ophiolite Complex, Norway (PTAL collection, https://www.ptal.eu). Here, distinct mineral assemblages record different stages of hydration and carbonation of ultramafic rocks [6].</p>
<p>We perform petrological and mineralogical analyses on thin sections to characterize the major and trace minerals and combine with Near Infrared (NIR) spectroscopy measurements. A set of spectral parameters are defined and compare to spectral parameters previously used on CRISM and OMEGA data [1, 4, 7, 8]. We study the significance of the mineralogical assemblages including nature of accessory minerals. Effect of the presence of accessory minerals on the NIR signal is investigated and their potential incidence on the amount of H<sub>2</sub>/CH<sub>4</sub> production in mafic or ultramafic system is discussed [5].</p>
<p>We started to apply the newly defined spectral parameters on several SCS on Mars. Results confirm local carbonation of earlier serpentinized rocks and suggest that different protoliths could have led to diversity of mineralogical associations in SCS on Mars. Multiple detection of brucite are also suggested for the first time on Mars. Altogether our results help to better describe key geochemical conditions of the SCS on Mars for habitability potential of the martian crust and Mars&#8217;s evolution.</p>
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<p>References:</p>
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<li>Brown, A. J., et al.&#160;<em>EPSL</em>1-2 (2010): 174-182.</li>
<li>Wiens, R.C.,&#160;et al.&#160;&#160;<em>Space Sci Rev</em><strong>217,&#160;</strong>4 (2021).</li>
<li>Horgan, B., et al.&#160;<em>Second International Mars Sample Return</em>. Vol. 2071. 2018.</li>
<li>Ody, A., et al.&#160;<em>JGR: Planets</em>2 (2013): 234-262.</li>
<li>Klein, F., et al. <em>Lithos</em>178 (2013): 55-69.</li>
<li>Bjerga, A., et al.&#160;<em>Lithos</em>227 (2015): 21-36.</li>
<li>Viviano-Beck et al, <em>JGR: Planets 11</em>8.9 (2013)</li>
<li>Viviano-Beck et al, <em>JGR: Planets 119.6</em>&#160;(2014)</li>
</ul>
Petrological implications for the production of methane and hydrogen in hyperalkaline springs from the Othrys ophiolite, Greece.
