The Perseverance rover has collected rock samples from the floor of Jezero crater, Mars, set to be returned to Earth through the Mars Sample Return (MSR) mission. These surface rocks are continuously bombarded by cosmic rays, resulting in the formation of cosmogenic nuclides. To accurately date these rocks and understand past geological events, precise estimates of nuclide production rates are essential. Here, we simulate neutron-induced cosmogenic nuclide production in the igneous rocks of Jezero crater using neutron flux data from the radiation assessment detector (RAD) and rock compositions from the planetary instrument for X-ray lithochemistry (PIXL). Our calculations focus on stable and long-lived isotopes up to Z = 27 (Co) over an exposure period of 100,000 years (0.1 Ma). The highest yields are observed for <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({}^{1}H\)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({}^{4}He\)</EquationSource> </InlineEquation>, followed by <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\({}^{12}C\)</EquationSource> </InlineEquation>, <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\({}^{13}C\)</EquationSource> </InlineEquation>, <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\({}^{15}N\)</EquationSource> </InlineEquation>, <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\({}^{23}Na\)</EquationSource> </InlineEquation>, <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\({}^{27}Al\)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\({}^{36}Cl\)</EquationSource> </InlineEquation>. We show that the predicted cumulative production over 0.1 Ma of long-lived radionuclides such as <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(^{10}Be\)</EquationSource> </InlineEquation> (T1/2 = 1.39 Ma), <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(^{26}Al\)</EquationSource> </InlineEquation> (0.72 Ma), <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(^{36}Cl\)</EquationSource> </InlineEquation> (0.301 Ma), and <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(^{41}Ca\)</EquationSource> </InlineEquation> (0.104 Ma) reaches ~ 108–109 nuclei per gram, a concentration well within the detection limits of current accelerator mass spectrometry (AMS) techniques. We project the impact of extended cosmic radiation exposure (1.4 billion years) on isotopic ratios, showing significant shifts in δ13C and δ15N values, whose correct interpretation is critical for astrobiology. These calculations can help define the instrumentation requirements for the future analysis of the Martian samples on Earth, ensuring accurate interpretation and helping to distinguish radiation effects from other planetary and biological cycles.

Recent production rates of cosmogenic nuclides in the igneous rocks of Jezero crater floor, Mars

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2025年12月27日

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M. -P. Zorzano,
A. C. García-Herrera,
J. Martín-Torres

摘要

The Perseverance rover has collected rock samples from the floor of Jezero crater, Mars, set to be returned to Earth through the Mars Sample Return (MSR) mission. These surface rocks are continuously bombarded by cosmic rays, resulting in the formation of cosmogenic nuclides. To accurately date these rocks and understand past geological events, precise estimates of nuclide production rates are essential. Here, we simulate neutron-induced cosmogenic nuclide production in the igneous rocks of Jezero crater using neutron flux data from the radiation assessment detector (RAD) and rock compositions from the planetary instrument for X-ray lithochemistry (PIXL). Our calculations focus on stable and long-lived isotopes up to Z = 27 (Co) over an exposure period of 100,000 years (0.1 Ma). The highest yields are observed for \({}^{1}H\) and \({}^{4}He\) , followed by \({}^{12}C\) , \({}^{13}C\) , \({}^{15}N\) , \({}^{23}Na\) , \({}^{27}Al\) and \({}^{36}Cl\) . We show that the predicted cumulative production over 0.1 Ma of long-lived radionuclides such as \(^{10}Be\) (T_1/2 = 1.39 Ma), \(^{26}Al\) (0.72 Ma), \(^{36}Cl\) (0.301 Ma), and \(^{41}Ca\) (0.104 Ma) reaches ~ 10⁸–10⁹ nuclei per gram, a concentration well within the detection limits of current accelerator mass spectrometry (AMS) techniques. We project the impact of extended cosmic radiation exposure (1.4 billion years) on isotopic ratios, showing significant shifts in δ¹³C and δ¹⁵N values, whose correct interpretation is critical for astrobiology. These calculations can help define the instrumentation requirements for the future analysis of the Martian samples on Earth, ensuring accurate interpretation and helping to distinguish radiation effects from other planetary and biological cycles.