Ionizing Radiation and Life

Dartnell, Lewis

doi:10.1089/ast.2010.0528

Cited by 161 publications

(132 citation statements)

References 322 publications

(400 reference statements)

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“…Anyhow, the trade-off between synthesis/degradation is positive. Data on the intensity of proton radiation on early Earth were reported and discussed (129). The cosmic rays flux into Earth's atmosphere was modeled (130) over the history of the planet based on the solar activity, on modulation of GCRs, and on estimations of the galactic star formation.…”

Section: Discussionmentioning

confidence: 99%

Meteorite-catalyzed syntheses of nucleosides and of other prebiotic compounds from formamide under proton irradiation

Saladino

Carota

Botta

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

168

157

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Liquid formamide has been irradiated by high-energy proton beams in the presence of powdered meteorites, and the products of the catalyzed resulting syntheses were analyzed by mass spectrometry. Relative to the controls (no radiation, or no formamide, or no catalyst), an extremely rich, variegate, and prebiotically relevant panel of compounds was observed. The meteorites tested were representative of the four major classes: iron, stony iron, chondrites, and achondrites. The products obtained were amino acids, carboxylic acids, nucleobases, sugars, and, most notably, four nucleosides: cytidine, uridine, adenosine, and thymidine. In accordance with theoretical studies, the detection of HCN oligomers suggests the occurrence of mechanisms based on the generation of radical cyanide species (CN·) for the synthesis of nucleobases. Given that many of the compounds obtained are key components of extant organisms, these observations contribute to outline plausible exogenous high-energy-based prebiotic scenarios and their possible boundary conditions, as discussed.origin of life | formamide | prebiotic syntheses | nucleosides | meteorites H ypothesizing formamide (FA) as parent molecule, we explored its potentiality in synthetic processes when exposed to proton irradiation. The purpose of this analysis is to verify a possible prebiotic scenario consisting of FA, considered here as starting one-carbon atom material, of proton beams mimicking solar energetic particles as energy source, and of meteorites as catalysts. The rationale of this approach is that the results could help in outlining exogenous prebiotic models and their boundaries.FA (NH 2 CHO) is becoming one of the most intensively studied precursors for prebiotic syntheses of compounds potentially relevant for the origin of life (1-4). FA is a ubiquitous molecule in the universe. It has been detected in galactic centers (Sgr A and Sgr B), in star-forming regions of dense molecular clouds, in high-mass young stellar objects, in the interstellar medium and in comets and satellites (5)(6)(7)(8)(9)(10)(11)(12)(13)(14).With the appropriate mineral as catalyst, different ensembles of intermediates of genetic and metabolic apparatuses are simultaneously synthesized from FA under thermal conditions (i.e., by heating liquid FA between 333 and 453 K at room pressure). DNA and RNA components (15-21), amino acids (22, 23), sugars (24), and carboxylic acids (25, 26) have been obtained. Minerals tune the selectivity of these transformations (1, 2), the mechanistic pathways for the synthesis of nucleobases requiring pyrimidine (27-30) or imidazole intermediates (31,32).Within the solar system, ionizing cosmic radiation is generated by the Sun [solar cosmic rays (SCRs), primarily protons accelerated by flares and coronal mass ejections to energies typically of tens to hundreds megaelectronvolts] and is also formed by particles coming from the deep universe [galactic cosmic rays (GCRs)] (33). The SCRs and GCRs differ in their components and energy spectra, but their overwhelming co...

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Section: Discussionmentioning

confidence: 99%

Meteorite-catalyzed syntheses of nucleosides and of other prebiotic compounds from formamide under proton irradiation

Saladino

Carota

Botta

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

168

157

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“…The excellent review by Dartnell (2011) mentions effects as diverse as: the modification of the atmospheric chemistry (which we discuss below), the excitation and ionization of atomic and molecular species, the creation of an ionosphere, ions driving atmospheric chemistry and potentially weather and climate dynamics, the possible influence on atmospheric lightning, the production of organic molecules within the atmosphere, the destruction of stratospheric ozone (see below), the possible sterilization of the planetary surface (see below), and the degradation of biosignatures (see below).…”

Section: Discussionmentioning

confidence: 99%

Galactic cosmic rays on extrasolar Earth-like planets

Grießmeier

Vakili

Stadelmann

et al. 2016

A&A

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Context. Theoretical arguments indicate that close-in terrestial exoplanets may have weak magnetic fields. As described in the companion article (Paper I), a weak magnetic field results in a high flux of galactic cosmic rays to the top of the planetary atmosphere. Aims. We investigate effects that may result from a high flux of galactic cosmic rays both throughout the atmosphere and at the planetary surface. Methods. Using an air shower approach, we calculate how the atmospheric chemistry and temperature change under the influence of galactic cosmic rays for Earth-like (N 2 -O 2 dominated) atmospheres. We evaluate the production and destruction rate of atmospheric biosignature molecules. We derive planetary emission and transmission spectra to study the influence of galactic cosmic rays on biosignature detectability. We then calculate the resulting surface UV flux, the surface particle flux, and the associated equivalent biological dose rates. Results. We find that up to 20% of stratospheric ozone is destroyed by cosmic-ray protons. The effect on the planetary spectra, however, is negligible. The reduction of the planetary ozone layer leads to an increase in the weighted surface UV flux by two orders of magnitude under stellar UV flare conditions. The resulting biological effective dose rate is, however, too low to strongly affect surface life. We also examine the surface particle flux: For a planet with a terrestrial atmosphere (with a surface pressure of 1033 hPa), a reduction of the magnetic shielding efficiency can increase the biological radiation dose rate by a factor of two, which is non-critical for biological systems. For a planet with a weaker atmosphere (with a surface pressure of 97.8 hPa), the planetary magnetic field has a much stronger influence on the biological radiation dose, changing it by up to two orders of magnitude. Conclusions. For a planet with an Earth-like atmospheric pressure, weak or absent magnetospheric shielding against galactic cosmic rays has little effect on the planet. It has a modest effect on atmospheric ozone, a weak effect on the atmospheric spectra, and a noncritical effect on biological dose rates. For planets with a thin atmosphere, however, magnetospheric shielding controls the surface radiation dose and can prevent it from increasing to several hundred times the background level.

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“…However, the same factors can also prove to be detrimental to the sustenance of complex biospheres (Dartnell 2011). …”

Section: Implications Of Seps For Exoplanetsmentioning

confidence: 99%

The Propitious Role of Solar Energetic Particles in the Origin of Life

Lingam

Dong

Fang

et al. 2018

ApJ

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We carry out 3-D numerical simulations to assess the penetration and bombardment effects of Solar Energetic Particles (SEPs), i.e. high-energy particle bursts during large flares and superflares, on ancient and current Mars. We demonstrate that the deposition of SEPs is non-uniform at the planetary surface, and that the corresponding energy flux is lower than other sources postulated to have influenced the origin of life. Nevertheless, SEPs may have been capable of facilitating the synthesis of a wide range of vital organic molecules (e.g. nucleobases and amino acids). Owing to the relatively high efficiency of these pathways, the overall yields might be comparable to (or even exceed) the values predicted for some conventional sources such as electrical discharges and exogenous delivery by meteorites. We also suggest that SEPs could have played a role in enabling the initiation of lightning. A notable corollary of our work is that SEPs may constitute an important mechanism for prebiotic synthesis on exoplanets around M-dwarfs, thereby mitigating the deficiency of biologically active ultraviolet radiation on these planets. Although there are several uncertainties associated with (exo)planetary environments and prebiotic chemical pathways, our study illustrates that SEPs represent a potentially important factor in understanding the origin of life.

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Ionizing Radiation and Life

Cited by 161 publications

References 322 publications

Meteorite-catalyzed syntheses of nucleosides and of other prebiotic compounds from formamide under proton irradiation

Meteorite-catalyzed syntheses of nucleosides and of other prebiotic compounds from formamide under proton irradiation

Galactic cosmic rays on extrasolar Earth-like planets

The Propitious Role of Solar Energetic Particles in the Origin of Life

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