Lifetime total radiation risk of cosmonauts for orbital and interplanetary flights.

This paper presents results of calculations of total radiation risk for cosmonauts over their lifetimes and assessments of possible shortening of life expectancy on the basis of generalized doses calculated for cosmonauts after a long term interplanetary and orbital space missions on "MIR" station and International Space Station with the use of mathematical expressions coming from a model of change mortality rate of mammals after irradiation. Tumor risk assessments for cosmonauts over lifetime after flights are also given. Dependences of the delayed radiation consequences mentioned above on flight duration, spacecraft shielding thicknesses, solar activity and cosmonauts' age are analyzed.     

Life before RNA

The hypothesis that life originated and evolved from linear informational molecules capable of facilitating their own catalytic replication is deeply entrenched. However, widespread acceptance of this paradigm seems oblivious to a lack of direct experimental support. Here, we outline the fundamental objections to the de novo appearance of linear, self-replicating polymers and examine an alternative hypothesis of template-directed coding of peptide catalysts by adsorbed purine bases. The bases (which encode biological information in modern nucleic acids) spontaneously self-organize into two-dimensional molecular solids adsorbed to the uncharged surfaces of crystalline minerals; their molecular arrangement is specified by hydrogen bonding rules between adjacent molecules and can possess the aperiodic complexity to encode putative protobiological information. The persistence of such information through self-reproduction, together with the capacity of adsorbed bases to exhibit enantiomorphism and effect amino acid discrimination, would seem to provide the necessary machinery for a primitive genetic coding mechanism.     

Eye light flashes on the Mir space station

The phenomenon of light flashes (LF) in eyes for people in space has been investigated onboard Mir. Data on particles hitting the eye have been collected with the SilEye detectors, and correlated with human observations. It is found that a nucleus in the radiation environment of Mir has roughly a 1% probability to cause an LF, whereas the proton probability is almost three orders of magnitude less. As a function of LET, the LF probability increases above 10 keV/micrometer, reaching about 5% at around 50 keV/micrometer.     

Long-term operation of "Orlan" space suits in the "Mir" orbiting station: experience obtained and its application

The started assembly of the International Space Station (ISS) and its further operation will call for a great number of extravehicular activity sorties (EVA) to be performed by ISS crews. Therefore, of great importance is to make use of the EVA experience gained by cosmonauts in the process of 15-year operation of the Mir orbiting station (OS). Over the 15-year period, Mir crewmembers wearing Orlan type semi-rigid space suits have accumulated 158 man/sorties from the orbiting station. Crewmembers used 15 suits in orbit and some of the suits were in operation for more than 3 years. The paper presents principal design features, which provide effective and safe operation of orbit-based suits, and briefly describes procedures for preparation and maintenance of suit systems, which ensure long-term operation of space suit in orbit. The paper gives results of the space suit modifications, presents suit performance characteristics and lists novel or upgraded components of the space suit and its systems. The paper also summarizes improvements in the Orlan type suits described in some earlier publications. They refer, in the first run, to the improvement of space suit operations characteristics and reliability, and the utilization of the Orlan type space suit in the ISS program. The paper analyses the experience gained and drawbacks detected and observations made, and gives statistical data on long-term space suit operations aboard the Mir station. The paper reviews certain problems in the process of EVAs performed from the station, and describes the ways of their solution as applied to the further utilization of the suit within the ISS program.     

Mass-independent fractionation of sulfur isotopes in Archean sediments: strong evidence for an anoxic Archean atmosphere

Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (> 2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O2 and high-O2 atmospheres. We show that in atmospheres with O2 concentrations < 10(-5) times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O2 concentrations > or = 10(-5) PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost. We conclude that the atmospheric O2 concentration must have been < 10(-5) PAL prior to 2.3 Ga.     

Study of cosmic rays and light flashes on board Space Station MIR: the SilEye experiment.

The SilEye experiment aims to study the cause and processes related to the anomalous Light Flashes (LF) perceived by astronauts in orbit and their relation with Cosmic Rays. These observations will be also useful in the study of the long duration manned space flight environment. Two PC-driven silicon detector telescopes have been built and placed aboard Space Station MIR. SilEye-1 was launched in 1995 and provided particles track and LF information; the data gathered indicate a linear dependence of FLF(Hz) ( 4 2) 10(3) 5.3 1.7 10(4) Fpart(Hz) if South Atlantic Anomaly fluxes are not included. Even though higher statistic is required, this is an indication that heavy ion interactions with the eye are the main LF cause. To improve quality and quantity of measurements, a second apparatus, SilEye-2, was placed on MIR in 1997, and started work from August 1998. This instrument provides energetic information, which allows nuclear identification in selected energy ranges; we present preliminary measurements of the radiation field inside MIR performed with SilEye-2 detector in June 1998.     

Halo White Dwarfs and Baryonic Dark Matter

We describe the formation of hot intergalactic gas along with baryonic remnants in galaxy halos. In this scenario, the mass and metallicity of the hot intracluster and intragroup gas relates directly to the production of baryonic remnants during the collapse of galactic halos. We construct a schematic but self-consistent model in which early bursts of star formation lead to a large remnant population in the halo, and to the outflow of stellar ejecta into the halo and ultimately the Local Group. We consider local as well as high redshift constraints on this scenario. This study suggests that the microlensing objects in the Galactic halo may predominantly be 0.5M white dwarfs, assuming that the initial mass function for early star formation favored the formation of intermediate mass stars with m 1M. However, the bulk of the baryonic dark matter in this scenario is associated with the ejecta of the white dwarf progenitors, and resides in the hot intergalactic medium.     

Cause and Effect At the Magnetopause

Recent analyses of spacecraft data, especially AMPTE/IRM data, provide a test of reconnection theory; an analysis for the signature of a local tangential stress balance in a one-dimensional time-stationary rotational discontinuity has left crucial questions unanswered. A key result is that the electron temperature profile inward through the magnetopause current sheet shows heating followed by cooling. Electrons must be one of the carriers of the current; hence this result reflects the sign of E · J in the frame of reference of the magnetopause current carriers. Since the current is directed from dawn to dusk, the inescapable conclusion is that the electric field must reverse within the current sheet. This is direct evidence of a load–dynamo combination; in that dynamo, energy is transferred from the solar wind plasma to the electromagnetic field. A dynamo is not included in the reconnection model which includes only the electrical load; therefore, we argue that the reconnection problem is improperly posed. A second compelling observation is a remarkable difference of the normal component of the plasma velocity between inbound and outbound crossings. For an inbound crossing (outward current meander) this component does reverse, but not quite as assumed in the reconnection model; on the other hand, for outbound crossings of the spacecraft (corresponding to erosion) there is no reversal at all. The normal component is approximately constant at 20 km s^-1, anti-Sunward throughout. Since the typical motion of the magnetopause is 10 km s^-1 this revealing result shows that solar wind plasma can go across the magnetopause, even onto closed field lines to feed the low latitude boundary layer. This is in stark contrast to the reconnection model where the plasma goes to open field lines. The interaction can be understood by appealing to Poynting's theorem, where E · J describes the net effect on or by the plasma. Time-dependent terms (even in the initial conditions) must be used so that it is possible to draw upon energy which has been stored locally in both electrical and magnetic forms. An extended discussion of observational results from ground-based, rocket, and satellite instruments indicate the impulsive nature of the solar wind–magnetospheric interaction. There is a lot of plasma involved in this interaction, over 10²⁷ ions electrons^-1 per second; the anti-Sunward flow takes place in the low latitude boundary layer. There is no flux catastrophe produced by this flow since the frozen-field theorem does not hold for plasma transfer across the magnetopause. The LLBL completely envelops the plasma sheet; the LLBL is the source of its plasma, not the plasma mantle as hypothesized in the reconnection model of the magnetotail. A number of serious errors have occurred in some articles in the literature on reconnection, and we list and discuss the most important of these. In the conclusion it is emphasized that the failure to provide a viable energy source, within the necessary spatial and temporal constraints, is responsible for the failure of reconnection model. This does not mean that the state of interconnection between the geomagnetic field and the interplanetary magnetic field can not change, but it does mean that the advocated process is not relevant to such changes. True reconnection requires that the electric field has a curl so that an electromotive force = E · dl = -d_Mdt exists through which energy can be interchanged with stored magnetic energy.