Constraints on a potential aerial biosphere on Venus: I. Cosmic rays

Dartnell, Lewis; Nordheim, Tom; Patel, Manish R.; Mason, Jon; Coates, A. J.; Jones, G. H.

doi:10.1016/j.icarus.2015.05.006

Cited by 47 publications

(70 citation statements)

References 92 publications

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“…The Geant4-based ATMOCOSMICS code , usually combined with MAGNE-TOCOSMICS, simulates the interaction of cosmic rays with the Earth's atmosphere, allowing the computation of the flux of secondaries at different atmospheric depths and/or altitudes. PLANETOCOSMICS is a more evolved code with respect to MAGNETOCOSMICS and ATMOCOSMICS, extensively applied in the field of planetary cosmic ray studies, including Mars (Gronoff et al, 2015;Ehresmann et al, 2011;Gurtner et al, 2005), Mercury (Gurtner et al, 2006), Venus Dartnell et al, 2015) and Titan (Gronoff et al (2009a(Gronoff et al ( , b, 2011. The recently developed DYASTIMA code includes many of the same features considered in PLANETOCOSMICS (e.g input of a custom atmospheric description, detection of primary and secondary fluxes and directions at given altitudes, user-defined primary cosmic ray spectra).…”

Section: Introductionmentioning

confidence: 99%

Solar energetic particle interactions with the Venusian atmosphere

et al. 2016

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Abstract. In the context of planetary space weather, we estimate the ion production rates in the Venusian atmosphere due to the interactions of solar energetic particles (SEPs) with gas. The assumed concept for our estimations is based on two cases of SEP events, previously observed in near-Earth space: the event in October 1989 and the event in May 2012. For both cases, we assume that the directional properties of the flux and the interplanetary magnetic field configuration would have allowed the SEPs' arrival at Venus and their penetration to the planet's atmosphere. For the event in May 2012, we consider the solar particle properties (integrated flux and rigidity spectrum) obtained by the Neutron Monitor Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model (Plainaki et al., 2010) applied previously for the Earth case and scaled to the distance of Venus from the Sun. For the simulation of the actual cascade in the Venusian atmosphere initiated by the incoming particle fluxes, we apply the DYASTIMA code, a Monte Carlo (MC) application based on the Geant4 software (Paschalis et al., 2014). Our predictions are afterwards compared to other estimations derived from previous studies and discussed. Finally, we discuss the differences between the nominal ionization profile due to galactic cosmic-ray-atmosphere interactions and the profile during periods of intense solar activity, and we show the importance of understanding space weather conditions on Venus in the context of future mission preparation and data interpretation.

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Section: Introductionmentioning

confidence: 99%

Solar energetic particle interactions with the Venusian atmosphere

et al. 2016

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“…To simulate the hadronic and electromagnetic interactions, and thus the evolution of secondary particle cascades as well as the atmospheric radiation dose, Dartnell et al (2015) based their studies on the QGSP_BIC_HP model using the quark-gluon-string (QGS) model for high-energy particle interactions and the binary cascade model (BIC) for particle energies below 10 GeV. As discussed in Herbst et al (2019a), the more accurate model to use is the FTFP_BERT_HP model, which is explicitly recommended for radiation protection and shielding applications.…”

Section: Simulation Setupmentioning

confidence: 99%

“…Because of the stable Venusian cloud lapse rates, therefore, airborne (nutrient-rich) particles could be sustained within the cloud layer for extended time intervals (Limaye et al 2018). Dartnell et al (2015) investigated whether GCRs and SEPs, including extreme SEP events from the historical record, could represent a constraint on the possibility of cloud-based life on Venus. This study, however, did not include modeling on water-based shape-, size-, and composition-mimicking detectors (phantoms), which more realistically describes the radiation effects in living organisms.…”

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confidence: 99%

Revisiting the cosmic-ray induced Venusian radiation dose in the context of habitability

Herbst

Banjac

Atri³

et al. 2019

A&A

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Context. Cosmic rays (CRs), which constantly bombard planetary magnetic fields and atmospheres, are the primary driver of atmospheric spallation processes. The higher the energy of these particles, the deeper they penetrate the planetary atmosphere, and the more likely interactions become with the ambient atmospheric material and the evolution of secondary particle showers. Aims. As recently discussed in the literature, CRs are the dominant driver of the Venusian atmospheric ionization and the induced radiation dose below ∼100 km. In this study, we model the atmospherically absorbed dose and the dose equivalent to the effect of cosmic rays in the context of Venusian habitability. Methods. The Atmospheric Radiation Interaction Simulator (AtRIS) was used to model the altitude-dependent Venusian absorbed dose and the Venusian dose equivalent. For the first time, we modeled the dose rates for different shape-, size-, and composition-mimicking detectors (phantoms): a CO 2 -based phantom, a water-based microbial cell, and a phantom mimicking human tissue. Results. Based on our new model approach, we give a reliable estimate of the altitude-dependent Venusian radiation dose in water-based microorganisms here for the first time. These microorganisms are representative of known terrestrial life. We also present a detailed analysis of the influence of the strongest ground-level enhancements measured at the Earth's surface, and of the impact of two historic extreme solar events on the Venusian radiation dose. Our study shows that because a phantom based on Venusian air was used, and because furthermore, the quality factors of different radiation types were not taken into account, previous model efforts have underestimated the radiation hazard for any putative Venusian cloud-based life by up to a factor of five. However, because we furthermore show that even the strongest events would not have had a hazardous effect on putative microorganisms within the potentially habitable zone (51 km -62 km), these differences may play only a minor role.

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“…The Venusian surface temperature (∼738 K) is too high to sustain liquid water, so based on Earth-centric definitions it is uninhabitable. At the cloud deck at ∼55 km, where atmospheric temperatures are close to those at Earth's surface, liquid water is more readily available and conditions are more amenable to sustaining life (Cockell 1999;Schulze-Makuch et al 2004;Dartnell et al 2015). The Jovian atmosphere has also been considered to be potentially habitable.…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Habitable Zones in Y Dwarf Atmospheres

Yates

Palmer

Biller

et al. 2017

ApJ

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We use a simple organism lifecycle model to explore the viability of an atmospheric habitable zone (AHZ), with temperatures that could support Earth-centric life, which sits above an environment that does not support life. To illustrate our model we use a cool Y dwarf atmosphere, such as WISE J085510.83-0714442.5 whose 4.5-5.2 micron spectrum shows absorption features consistent with water vapour and clouds. We allow organisms to adapt to their atmospheric environment (described by temperature, convection, and gravity) by adopting different growth strategies that maximize their chance of survival and proliferation. We assume a constant upward vertical velocity through the AHZ. We found that the organism growth strategy is most sensitive to the magnitude of the atmospheric convection. Stronger convection supports the evolution of more massive organisms. For a purely radiative environment we find that evolved organisms have a mass that is an order of magnitude smaller than terrestrial microbes, thereby defining a dynamical constraint on the dimensions of life that an AHZ can support. Based on a previously defined statistical approach we infer that there are of order 10 9 cool Y brown dwarfs in the Milky Way, and likely a few tens of these objects are within ten parsecs from Earth. Our work also has implications for exploring life

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Constraints on a potential aerial biosphere on Venus: I. Cosmic rays

Cited by 47 publications

References 92 publications

Solar energetic particle interactions with the Venusian atmosphere

Solar energetic particle interactions with the Venusian atmosphere

Revisiting the cosmic-ray induced Venusian radiation dose in the context of habitability

Atmospheric Habitable Zones in Y Dwarf Atmospheres

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