Survival and death of the haloarchaeon Natronorubrum strain HG-1 in a simulated martian environment

Halophilic archaea are of interest to astrobiology due to their survival capabilities in desiccated and high salt environments. The detection of remnants of salty pools on Mars stimulated investigations into the response of haloarchaea to martian conditions. Natronorubrum sp. strain HG-1 is an extremely halophilic archaeon with unusual metabolic pathways, growing on acetate and stimulated by tetrathionate. We exposed Natronorubrum strain HG-1 to ultraviolet (UV) radiation, similar to levels currently prevalent on Mars. In addition, the effects of low temperature (4, −20, and −80 °C), desiccation, and exposure to a Mars soil analogue from the Atacama desert on the viability of Natronorubrum strain HG-1 cultures were investigated. The results show that Natronorubrum strain HG-1 cannot survive for more than several hours when exposed to UV radiation equivalent to that at the martian equator. Even when protected from UV radiation, viability is impaired by a combination of desiccation and low temperature. Desiccating Natronorubrum strain HG-1 cells when mixed with a Mars soil analogue impaired growth of the culture to below the detection limit. Overall, we conclude that Natronorubrum strain HG-1 cannot survive the environment currently present on Mars. Since other halophilic microorganisms were reported to survive simulated martian conditions, our results imply that survival capabilities are not necessarily shared between phylogenetically related species.     

Relation between galactic and solar cosmic radiation at aviation altitude

Cosmic radiation bombards us at high altitude with ionizing particles; the radiation has a galactic component, which is normally dominant, and a component of solar origin. Cosmic ray particles are the primary source of ionization in the atmosphere above 1 km; below 1 km radon is a dominant source of ionization in many areas.     

Responses of ionospheric foF2 to geomagnetic activities in Hainan

Responses of low-latitude ionospheric critical frequency of F2 layer to geomagnetic activities in different seasons and under different levels of solar activity are investigated by analyzing the ionospheric foF2 data from DPS-4 Digisonde in Hainan Observatory during 2002–2005. The results are as follows: (1) the response of foF2 to geomagnetic activity in Hainan shows obvious diurnal variation except for the summer in low solar activity period. Generally, geomagnetic activity will cause foF2 to increase at daytime and decrease at nighttime. The intensity of response of foF2 is stronger at nighttime than that at daytime; (2) seasonal dependence of the response of foF2 to geomagnetic activity is very obvious. The negative ionospheric storm effect is the strongest in summer and the positive ionospheric storm effect is the strongest in winter; (3) the solar cycle has important effect on the response of foF2 to geomagnetic activity in Hainan. In high solar activity period, the diurnal variation of the response of foF2 is very pronounced in each season, and the strong ionospheric response can last several days. In low solar activity period, ionospheric response has very pronounced diurnal variation in winter only; (4) the local time of geomagnetic activities occurring also has important effect on the responses of foF2 in Hainan. Generally, geomagnetic activities occurred at nighttime can cause stronger and longer responses of foF2 in Hainan.     

The organic aerosols of Titan

A dark reddish organic solid, called tholin, is synthesized from simulated Titanian atmospheres by irradiation with high energy electrons in a plasma discharge. The visible reflection spectrum of this tholin is found to be similar to that of high altitude aerosols responsible for the albedo and reddish color of Titan. The real (n) and imaginary (k) parts of the complex refractive index of thin films of Titan tholin prepared by continuous D.C. discharge through a 0.9 N₂/0.1 CH₄ gas mixture at 0.2 mb is determined from x-ray to microwave frequencies. Values of n (1.65) and k (0.004 to 0.08) in the visible are consistent with deductions made by ground-based and spaceborne observations of Titan. Many infrared absorption features are present in k(λ), including the 4.6 μm nitrile band. Molecular analysis of the volatile component of this tholin was performed by sequential and non-sequential pyrolytic gas chromatography/mass spectrometry. More than one hundred organic compounds are released; tentative identifications include saturated and unsaturated aliphatic hydrocarbons, substituted polycyclic aromatics, nitriles, amines, pyrroles, pyrazines, pyridines, pyrimidines, and the purine, adenine. In addition, acid hydrolysis produces a racemic mixture of biological and non-biological amino acids. Many of these molecules are implicated in the origin of life on Earth, suggesting Titan as a contemporary laboratory environment for prebiological organic chemistry on a planetary scale.     

Fast Probabilistic Particle Identification algorithm using silicon strip detectors

Active detectors used as radiation monitors in space are not usually able to perform Particle Identification (PID). Common techniques need energy loss spectra with high statistics to estimate ion abundances. The ALTEA-space detector system is a set of silicon strip particle telescopes monitoring the radiation environment on board the International Space Station since July 2006 with real-time telemetry capabilities. Its large geometrical factor due to the concurrent use of six detectors permits the acquisition of good energy loss spectra even in a short period of observation. In this paper we present a novel Fast Probabilistic Particle Identification (FPPI) algorithm developed for the ALTEA data analysis in order to perform nuclear identification with low statistics and, with some limitations, also in real time.     

Impact of geomagnetic variation over sub-auroral ionospheric region during high solar activity year 2014

The present work is an attempt to evaluate the impact of changing space weather condition over sub-auroral ionosphere during high solar activity year 2014. In view of this, the GPS based TEC along with Ionosonde data over Indian permanent scientific base “Maitri”, Antarctica (70°46′00″S, 11°43′56″E) has been utilized. The results suggested that the nature of ionospheric responses to the geomagnetic disturbances not only depended upon the status of high latitudinal electro-dynamic processes but also influenced by the seasonal variations. The results revel both negative and positive type of ionospheric response in a single year but during different seasons. The study suggested that the combination of equator-ward plasma transportation along with ionospheric compositional changes causes a negative ionospheric impact especially during summer and equinox seasons. However, the combination of pole-ward contraction of the oval region along with particle precipitation may lead to exhibit positive ionospheric response during the winter season. The plasma transportation direction has been validated with the help of convection boundary (HM boundary) deduced with the help of SuperDARN observations. The ground based ionosonde observations clearly provided the evidence of deep penetration of high energetic particles up to the E-layer heights which results a sudden and strong appearance of E-layer. The strengthening of E-layer is responsible for modification of auroral electrojet and field-aligned current system. Also, the sudden appearance of E-layer along with a decrease in F-layer electron density suggested the dominance of NO⁺ over O⁺ in a considered region under geomagnetic disturbed condition.     

Neurobiological problems in long-term deep space flights.

Future missions in space may involve long-term travel beyond the magnetic field of the Earth, subjecting astronauts to radiation hazards posed by solar flares and galactic cosmic rays, altered gravitation fields and physiological stress. Thus, it is critical to determine if there will be any reversible or irreversible, detrimental neurological effects from this prolonged exposure to space. A question of particular importance focuses on the long-term effects of the space environment on the central nervous system (CNS) neuroplasticity, with the potential acute and/or delayed effects that such perturbations might entail. Although the short-term effects of microgravity on neural control were studied on previous low earth orbit missions, the late consequences of stress in space, microgravity and space radiation have not been addressed sufficiently at the molecular, cellular and tissue levels. The possibility that space flight factors can interact influencing the neuroplastic response in the CNS looms critical issue not only to understand the ontogeny of the CNS and its functional integrity, but also, ultimately the performance of astronauts in extended space forays. The purpose of this paper is to review the neurobiological modifications that occur in the CNS exposed to the space environment, and its potential consequences for extended deep space flight.