In-situ resource utilization technologies for Mars life support systems.

The atmosphere of Mars has many of the ingredients that can be used to support human exploration missions. It can be "mined" and processed to produce oxygen, buffer gas, and water, resulting in significant savings on mission costs. The use of local materials, called ISRU (for in-situ resource utilization), is clearly an essential strategy for a long-term human presence on Mars from the standpoints of self-sufficiency, safety, and cost. Currently a substantial effort is underway by NASA to develop technologies and designs of chemical plants to make propellants from the Martian atmosphere. Consumables for life support, such as oxygen and water, will probably benefit greatly from this ISRU technology development for propellant production. However, the buffer gas needed to dilute oxygen for breathing is not a product of a propellant production plant. The buffer gas needs on each human Mars mission will probably be in the order of metric tons, primarily due to losses during airlock activity. Buffer gas can be separated, compressed, and purified from the Mars atmosphere. This paper discusses the buffer gas needs for a human mission to Mars and consider architectures for the generation of buffer gas including an option that integrates it to the propellant production plant.     

Exobiological exploration of Mars.

Of all the other planets in the solar system, Mars remains the most promising for further elucidating concepts about chemical evolution and the origin of life. Strategies were developed to pursue three exobiological objectives for Mars exploration: determining the abundance and distribution of the biogenic elements and organic compounds, detecting evidence of an ancient biota on Mars, and determining whether indigenous organisms exist anywhere on the planet. The three strategies are quite similar and, in fact, share the same sequence of phases. In the first phase, each requires global reconnaissance and remote sensing by orbiters to select sites of interest for detailed in situ analyses. In the second phase, lander missions are conducted to characterize the chemical and physical properties of the selected sites. The third phase involves conducting "critical" experiments at sites whose properties make them particularly attractive for exobiology. These critical experiments would include, for example, identification of organics, detection of fossils, and detection of extant life. The fourth phase is the detailed analysis of samples returned from these sites in Earth-based laboratories to confirm and extend previous discoveries. Finally, in the fifth phase, human exploration is needed to establish the geological settings for the earlier findings or to discover and explore sites that are not accessible to robotic spacecraft.     

Characteristics and formation of amino acids and hydroxy acids of the Murchison meteorite.

Eight characteristics of the unique suite of amino acids and hydroxy acids found in the Murchison meteorite can be recognized on the basis of detailed molecular and isotopic analyses. The marked structural correspondence between the alpha-amino acids and alpha-hydroxy acids and the high deuterium/hydrogen ratio argue persuasively for their formation by aqueous phase Strecker reactions in the meteorite parent body from presolar, i.e., interstellar, aldehydes, ketones, ammonia, and hydrogen cyanide. The characteristics of the meteoritic suite of amino acids and hydroxy acids are briefly enumerated and discussed with regard to their consonance with this interstellar-parent body formation hypothesis. The hypothesis has interesting implications for the organic composition of both the primitive parent body and the presolar nebula.     

Galactic cosmic rays and cell-hit frequencies outside the magnetosphere.

An evaluation of the exposure of space travelers to galactic cosmic radiation outside the earth's magnetosphere is made by calculating fluences of high-energy primary and secondary particles with various charges traversing a sphere of area 100 microns2. Calculations relating to two shielding configurations are presented: the center of a spherical aluminum shell of thickness 1 g/cm2, and the center of a 4 g/cm2 thick aluminum spherical shell within which there is a 30 g/cm2 diameter spherical water phantom with the point of interest 5 g/cm2 from the surface. The area of 100 microns2 was chosen to simulate the nucleus of a cell in the body. The frequencies as a function of charge component in both shielding configurations reflects the odd-even disparity of the incident particle abundances. For a three-year mission, 33% of the cells in the more heavily shielded configuration would be hit by at least one particle with Z greater than 10. Six percent would be hit by at least two such particles. This emphasizes the importance of studying single high-Z particle effects both on cells which might be "at risk" for cancer induction and on critical neural cells or networks which might be vulnerable to inactivation by heavy charged particle tracks. Synergistic effects with the more numerous high-energy protons and helium ions cannot be ruled out. In terms of more conventional radiation risk assessment, the dose equivalent decreased by a factor of 2.85 from free space to that in the more heavily shielded configuration. Roughly half of this was due to the decrease in energy deposition (absorbed dose) and half to the decrease in biological effectiveness (quality factor).     

Continuous tracking of cmes using MICA, andLASCO C2 and C3 coronagraphs

In this work we have tracked coronal mass ejections observed with the ground based Mirror Coronagraph for Argentina (MICA) and the Large Angle and Spectroscopic Coronagraph (LASCO) C2 and C3 on board of the Solar and Heliospheric Observatory (SOHO). The MICA telescope is located at El Leoncito (31.8 S, 69.3 W), San Juan (Argentina), since 1997 as part of a bilateral scientific project between Germany and Argentina. SOHO is a project of international cooperation between ESA and NASA. Together these instruments are able to observe the solar corona ranging from 1.05 to 32 solar radii. MICA images the Fe XIV emission line corona and LASCO coronagraphs observe the Thomson scattered white light corona. We have selected events for which there are observations from the three coronagraphs. Using the composite data we were able to obtain height-time diagrams for the corresponding dynamical coronal features traveling outwards in order to determine some of their kinematical properties, i.e., plane of sky velocity and acceleration.     

The atmospheric radiation response to solar-particle-events.

High-energy solar particles, produced in association with solar flares and coronal mass ejections, occasionally bombard the earth's atmosphere. resulting in radiation intensities additional to the background cosmic radiation. Access of these particles to the earth's vicinity during times of geomagnetic disturbances are not adequately described by using static geomagnetic field models. These solar fluxes are also often distributed non uniformly in space, so that fluxes measured by satellites obtained at great distances from the earth and which sample large volumes of space around the earth cannot be used to predict fluxes locally at the earth's surface. We present here a method which uses the ground-level neutron monitor counting rates as adjoint sources of the flux in the atmosphere immediately above them to obtain solar-particle effective dose rates as a function of position over the earth's surface. We have applied this approach to the large September 29-30, 1989 ground-level event (designated GLE 42) to obtain the magnitude and distribution of the solar-particle effective dose rate from an atypically large event. The results of these calculations clearly show the effect of the softer particle spectra associated with solar particle events, as compared with galactic cosmic rays, results in a greater sensitivity to the geomagnetic field, and, unlike cosmic rays, the near-absence of a "knee" near 60 degrees geomagnetic latitude.     

HZE-dosimetry on MIR92, IML-1 and D-2

Nuclear track detectors were used to measure the integral Linear Energy Transfer (LET) spectra above 1 GeV per cm water behind the complex material shielding inside a spacecraft. The measurements are compared with predictions of the contribution of high charge, high energy HZE particles of the galactic cosmic radiation taking into account the influence of solar and geomagnetic modulation and shielding by matter.     

Surface tension-driven flows in horizontal liquid metal layers

The problem of surface tension-driven flows in horizontal liquid layers has been studied experimentally, and theoretically by direct numerical simulation and small perturbation analysis. We focus our attention on situations in which the depth of the fluid (liquid tin; small Prandtl number, Pr=0.015) is small enough to ensure the predominance of the surface tension forces over those due to the buoyancy. The surface velocity has been experimentally obtained for liquid tin layer with various aspect ratio (length to height) in the range 5<A<83. The thermal gradients are ranged from 5 to 40°K/cm. In the numerical study, the Navier-Stokes and energy equations are solved by an efficient finite difference technique. The parameters governing the flow behaviour in the liquid are varied to determine their effects on thermocapillary convection: the Reynolds number 10<Re<210⁴ and the aspect ratio 2<A<25; with Pr kept constant at Pr=0.015. The linear eigenequation resulting from small spatial disturbances of the Couette flow solution is solved using an Tau-Chebyshev approximation. A notable feature of the theoretical study is the totally different end circulations. In the region near the cold wall a multicell structure is evident. This agrees with the eigensolution which is of complex type, indicating spatial periodicity. In the hot wall region the flow is accelerated to reach the velocity value for the fully-developed Couette flow which is reached under conditions such as Re/A<20. The transition from viscous to boundary layer regime occurs for a critical value (Re/A)_c of nearly about 200, as deduced from the numerical and experimental results.     

Some comparisons of orbit determination and parameter estimation based on LAGEOS 1 and LAGEOS 2 data

The modelling accuracy of the LAGEOS 1 orbit was continously improved since its launch in 1976. In spite of these experiences the modelling accuracy of LAGEOS 2 is still about 20 per cent worse. Considering e. g. only the influence of different gravity field models it has been shown that the orbital fits for arc lengths of one month is generally about 25 mm for LAGEOS 1 and more than 30 mm for LAGEOS 2. This is mainly due to the fact that LAGEOS 2 has not yet been used for the determination of most gravity field models. The influences of different model parameters on the estimation of station coordinates, Earth rotation parameters, the geogravitational coefficient, the radiation pressure coefficient, and the empirical acceleration has been studied. The differences and peculiarities of both satellites are discussed. Although the analysis of LAGEOS 2 data still does not reach the high level of LAGEOS 1 combination solutions using both satellites allow new insights, higher accuracies, and a higher time resolution for the parameters and phenomena investigated.     

Formation of amino acid precursors in cometary ice environments by cosmic radiation.

Cometary ices are believed to contain water, carbon monoxide, methane and ammonia, and are possible sites for the formation and preservation of organic compounds relating to the origin of life. Cosmic rays, together with ultraviolet light, are among the most effective energy sources for the formation of organic compounds in space. In order to study the possibility of the formation of amino acids in comets or their precursory bodies (interstellar dust grains), several types of ice mixtures made in a cryostat at 10 K ("simulated cometary ices") were irradiated with high energy protons. After irradiation, the volatile products were analyzed with a quadrupole mass spectrometer, while temperature of the cryostat was raised to room temperature. The non-volatile products remaining in the cryostat at room temperature were collected with water. They were acid-hydrolyzed, and analyzed by ion-exchange chromatography. When an ice mixture of carbon monoxide (or methane), ammonia and water was irradiated, some hydrocarbons were formed, and amino acids such as glycine and alanine were detected in the hydrolyzate. These results suggest the possible formation of "amino acid precursors" (compounds yielding amino acids after hydrolysis) in interstellar dust grains by cosmic radiation. We previously reported that amino acid precursors were formed when simulated primitive planetary atmospheres were irradiated with cosmic ray particles. It will be of great interest to compare the amount of bioorganic compounds that were formed in the primitive earth and that brought by comets to the earth.