Martian sub-surface ionising radiation: biosignatures and geology

Abstract. The surface of Mars, unshielded by thick atmosphere or global magnetic field, is exposed to high levels of cosmic radiation. This ionising radiation field is deleterious to the survival of dormant cells or spores and the persistence of molecular biomarkers in the subsurface, and so its characterisation is of prime astrobiological interest. Here, we present modelling results of the absorbed radiation dose as a function of depth through the Martian subsurface, suitable for calculation of biomarker persistence. A second major implementation of this dose accumulation rate data is in application of the optically stimulated luminescence technique for dating Martian sediments. We present calculations of the dose-depth profile in the Martian subsurface for various scenarios: variations of surface composition (dry regolith, ice, layered permafrost), solar minimum and maximum conditions, locations of different elevation (Olympus Mons, Hellas basin, datum altitude), and increasing atmospheric thickness over geological history. We also model the changing composition of the subsurface radiation field with depth compared between Martian locations with different shielding material, determine the relative dose contributions from primaries of different energies, and discuss particle deflection by the crustal magnetic fields.

[1]  John M. Ward,et al.  Modelling the surface and subsurface Martian radiation environment: Implications for astrobiology , 2007 .

[2]  T. Stenström,et al.  Thermophilic, anaerobic bacteria isolated from a deep borehole in granite in Sweden. , 1994, Proceedings of the National Academy of Sciences of the United States of America.

[3]  Michael H. Carr,et al.  Water on Mars , 1987, Nature.

[4]  Gerhard Kminek,et al.  The effect of ionizing radiation on the preservation of amino acids on Mars , 2006 .

[5]  K. Venkateswaran,et al.  Rapid inactivation of seven Bacillus spp. under simulated Mars UV irradiation , 2006 .

[6]  Ness,et al.  Global distribution of crustal magnetization discovered by the mars global surveyor MAG/ER experiment , 1999, Science.

[7]  Sheila A. Thibeault,et al.  Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays , 1998 .

[8]  M. Hecht,et al.  Evidence that the reactivity of the martian soil is due to superoxide ions. , 2000, Science.

[9]  C. Cockell,et al.  The ultraviolet environment of Mars: biological implications past, present, and future. , 2000, Icarus.

[10]  L. Orgel,et al.  Prebiotic chemistry and the origin of the RNA world. , 2004, Critical reviews in biochemistry and molecular biology.

[11]  M. le Maire,et al.  Protein gamma-radiolysis in frozen solutions is a macromolecular surface phenomenon: fragmentation of lysozyme, citrate synthase and alpha-lactalbumin in native or denatured states. , 2000, International journal of radiation biology.

[12]  Gerhard Kminek,et al.  ExoMars - searching for life on the Red Planet , 2006 .

[13]  R. Katz,et al.  Theory of RBE for heavy ion bombardment of dry enzymes and viruses. , 1967, Radiation research.

[14]  D. Goodhead.  Mechanisms for the biological effectiveness of high-LET radiations. , 1999, Journal of radiation research.

[15]  Jan-Peter Muller,et al.  Evidence from the Mars Express High Resolution Stereo Camera for a frozen sea close to Mars' equator , 2005, Nature.

[16]  G. Horneck,et al.  Natural Transfer of Viable Microbes in Space: 1. From Mars to Earth and Earth to Mars , 2000 .

[17]  James W. Rice,et al.  Mars chronology: assessing techniques for quantifying surficial processes , 2004 .

[18]  Rudolf Rieder,et al.  Chemical Composition of Rocks and Soils at the Pathfinder Site , 2001 .

[19]  M. Gurtner,et al.  Atmocosmics:. a Geant 4 Code for Computing the Interaction of Cosmic Rays with the Earth's Atmosphere , 2005 .

[20]  Bernard H. Foing,et al.  Amino acid photostability on the Martian surface , 2005 .

[21]  J. Rossier,et al.  Lysozyme fragmentation induced by gamma-radiolysis. , 1997, International journal of radiation biology.

[22]  G. Nelson,et al.  Fundamental space radiobiology. , 2003, Gravitational and space biology bulletin : publication of the American Society for Gravitational and Space Biology.

[23]  F. Forget.  Scatter Infrared Radiation Warming Early Mars with Carbon Dioxide Clouds , 2008 .

[24]  B. Simoneit,et al.  Biomarkers as Tracers for Life on Early Earth and Mars , 1996, Origins of life and evolution of the biosphere.

[25]  G. Flynn.  The delivery of organic matter from asteroids and comets to the early surface of Mars , 1996 .

[26]  S. S. Kim,et al.  Concepts and approaches to in situ luminescence dating of Martian sediments. , 2003, Radiation measurements.

[27]  Jeffrey R. Johnson,et al.  In Situ Evidence for an Ancient Aqueous Environment at Meridiani Planum, Mars , 2004, Science.

[28]  N. Hoffman.  Modern Geothermal Gradients on Mars and Implications for Subsurface Liquids , 2001 .

[29]  J L Bada,et al.  Racemization and the origin of optically active organic compounds in living organisms. , 1987, Bio Systems.

[30]  M. Engel,et al.  Distribution and enantiomeric composition of amino acids in the Murchison meteorite , 1982, Nature.

[31]  R. Phillips,et al.  Mars' volatile and climate history , 2001, Nature.

[32]  C. Cockell.  The ultraviolet history of the terrestrial planets — implications for biological evolution , 2000 .

[33]  B. Clark.  Surviving the limits to life at the surface of Mars , 1998 .

[34]  S. Squyres.  The history of water on Mars , 1984 .

[35]  V. Krasnopolsky.  Some problems related to the origin of methane on Mars , 2006 .

[36]  A. S. Kozyrev,et al.  Soil Water Content on Mars as Estimated from Neutron Measurements by the HEND Instrument Onboard the 2001 Mars Odyssey Spacecraft , 2004 .

[37]  L. Richter,et al.  Neutron activation analysis, gamma ray spectrometry and radiation environment monitoring instrument concept: GEORAD , 2005 .

[38]  A. Zent,et al.  On the thickness of the oxidized layer of the Martian regolith. , 1998, Journal of geophysical research.

[39]  Bernd Kromer,et al.  Solar proton events in cosmogenic isotope data , 2006 .

[40]  R. Haberle.  Early Mars Climate Models , 1998 .

[41]  C P McKay,et al.  On the possibility of chemosynthetic ecosystems in subsurface habitats on Mars. , 1992, Icarus.

[42]  C. Baumstark-Khan,et al.  Life under Conditions of Ionizing Radiation , 2002 .

[43]  S. McKeever,et al.  Development of methods for in situ dating of martian sediments , 2006 .

[44]  G. Flynn,et al.  The delivery of organic matter from asteroids and comets to the early surface of Mars. , 1996, Earth, moon, and planets.

[45]  F Forget,et al.  Warming early Mars with carbon dioxide clouds that scatter infrared radiation. , 1997, Science.

[46]  J. Beringer,et al.  Validation of Geant4 hadronic physics , 2003, 2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515).

[47]  R. Greeley,et al.  Geomorphologic Evidence for Liquid Water , 2001 .

[48]  A. V. Blinov,et al.  Sterilization of Martian surface by cosmic radiation , 2002 .

[49]  Rudolf Beaujean,et al.  Precursor Measurements of the Mars Surface Radiation Environment with the Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) , 2009 .

[50]  J. Bridges,et al.  Luminescence dating on Mars: OSL characteristics of Martian analogue materials and GCR dosimetry , 2006 .

[51]  E. Sagstuen,et al.  Alanine Radicals, Part 4: Relative Amounts of Radical Species in Alanine Dosimeters after Exposure to 6–19 MeV Electrons and 10 kV–15 MV Photons , 2003, Radiation research.

[52]  Marco Giuranna,et al.  Detection of Methane in the Atmosphere of Mars , 2004, Science.

[53]  F. Hutchinson.  RADIATION EFFECTS ON MACROMOLECULES OF BIOLOGICAL IMPORTANCE. , 1963, Annual review of nuclear science.

[54]  R. Jaumann,et al.  Geomorphological Record of Water-related Erosion on Mars , 2002 .

[55]  H. Melosh,et al.  The rocky road to panspermia , 1988, Nature.

[56]  K. Amako,et al.  Comparison of Geant4 electromagnetic physics models against the NIST reference data , 2005, IEEE Transactions on Nuclear Science.

[57]  M. A. Moreno.  Microorganism transport from Earth to Mars , 1988, Nature.

[58]  J. Cain,et al.  An n = 90 internal potential function of the Martian crustal magnetic field , 2003 .