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PubMed2000

Solar wind record on the moon: deciphering presolar from planetary nitrogen.

Ion microprobe analyses show that solar wind nitrogen associated with solar wind hydrogen implanted in the first tens of nanometers of lunar regolith grains is depleted in 15N by at least 24% relative to terrestrial atmosphere, whereas a nonsolar component associated with deuterium-rich hydrogen, detected in silicon-bearing coatings at the surface of some ilmenite grains, is enriched in 15N. Systematic enrichment of 15N in terrestrial planets and bulk meteorites relative to the protosolar gas cannot be explained by isotopic fractionation in nebular or planetary environments but requires the contribution of 15N-rich compounds to the total nitrogen in planetary materials. Most of these compounds are possibly of an interstellar origin and never equilibrated with the 15N-depleted protosolar nebula.

Argon↗
PubMed2005

Human behavioral research in space: quandaries for research subjects and researchers.

With the advent of long-duration spaceflight on board the International Space Station (ISS) and possible future missions beyond low Earth orbit (LEO) such as Mars, it is critical that those at NASA have a realistic assessment of the challenges that will face individuals on long-duration missions so that they can develop preventive and real-time countermeasures to behavioral health issues. While space travellers are very interested in having countermeasures to the deleterious effects of space missions, they have a powerful disincentive to participate in this research if they feel it could in any way negatively affect their flight status. The behavioral issues of isolation and confinement for extended-duration space missions are reviewed. Areas of basic and clinical behavioral research are listed. And the classical clinical model for research is not considered appropriate for the current configuration of the space program. The use of analogue environments and advanced statistical analysis are suggested as ways to address the limited spaceflight research opportunities. The challenge of research subject or patient confidentiality vs. mission safety and issues of personal flight status are addressed.

Adaptation, Physiological↗
PubMedDate not supplied

Lunar exploration and development--a sustainable model.

A long-term goal of space exploration is the development of a lunar settlement that will not only be largely self-sufficient but also contribute to the economy of the Earth-Moon system. Proposals for lunar mining and materials processing developments, as well as tourism-based applications, have appeared in the literature for many years. However, so great are the technical and financial difficulties associated with sustained lunar development that, more than 30 years after the end of the Apollo programme, there have been no practical advances towards this goal. While this may soon be remedied by a series of proposed unmanned orbiters, landers and rovers, the philosophy of lunar exploration and development remains the same as it has for decades: conquer, exploit, and ignore the consequences. By contrasting the well-recognised problems of Earth orbital debris and the barely recognised issue of intentional spacecraft impacts on the lunar surface, this paper illustrates the need for a new model for lunar exploration and development. This new paradigm would assign a value to the lunar environment and provide a balance between protection and exploitation, creating, in effect, a philosophy of sustainable development for the Moon. It is suggested that this new philosophy should be an integral part of any future strategy for lunar colonisation.

Containment of Biohazards↗
PubMed1994

The lunar environment as a fractional-gravity biological laboratory.

A quarter of a century ago men stepped upon the lunar surface and established the possibility of human expansion beyond Earth. When humans return to the moon to occupy it with greater permanency, an applied lunar biological laboratory would provide a means of conducting experiments on the long-term effects of fractional gravity in animals and plants and provide necessary data to enhance the health, safety and well-being of lunar workers and inhabitants. In-depth studies can go beyond zero-g observations, on-orbit centrifuge studies, and ground-based research providing important insight into continuous 1/6-g effects on biological systems. Studies concentrating on development, gravity sensing, and adaptation/readaptation would provide preliminary data on whether long-term fractional gravity is detrimental or compromising to fundamental biological function. Food production research in 1/6-g would provide important information for on site application to improve the yield and quality of food (animal and plant) produced in the unique lunar environment. The purpose of this paper is to discuss some examples of the major gravitational biology areas that could be studied on the moon and applied to lunar population needs utilizing lunar biological facilities and continuous fractional gravity.

Adaptation, Physiological↗
PubMed2005

Implications of the space radiation environment for human exploration in deep space.

Human exploration of the solar system beyond Earth's orbit will entail many risks for the crew on these deep space missions. One of the most significant health risks is exposure to the harsh space radiation environment beyond the protection provided by the Earth's intrinsic magnetic field. Crew on exploration missions will be exposed to a complex mixture of very energetic particles. Chronic exposures to the ever-present background galactic cosmic ray (GCR) spectrum consisting of all naturally occurring chemical elements are combined with sporadic, possibly acute exposures to large fluxes of solar energetic particles, mainly protons and alpha particles. The background GCR environment is mainly a matter of concern for stochastic effects, such as the induction of cancer with subsequent mortality in many cases, and late deterministic effects, such as cataracts and possible damage to the central nervous system. Unfortunately, the actual risks of cancer induction and mortality owing to the very important high-energy heavy ion component of the GCR spectrum are essentially unknown. The sporadic occurrence of extremely large solar energetic particle events (SPE), usually associated with intense solar activity, is also a major concern for the possible manifestation of acute effects from the accompanying high doses of such radiations, especially acute radiation syndrome effects such as nausea, emesis, haemorrhaging or, possibly, even death. In this presentation, an overview of the space radiation environment, estimates of the associated body organ doses and equivalent doses and the potential biological effects on crew in deep space are presented. Possible methods of mitigating these radiations, thereby reducing the associated risks to crew are also described.

Astronauts↗
PubMedDate not supplied

Space radiation dose estimates on the surface of Mars.

A future goal of the U.S. space program is a commitment to the manned exploration and habitation of Mars. An important consideration of such missions is the exposure of crew members to the damaging effects of ionizing radiation from high-energy galactic cosmic ray fluxes and solar proton flares. The crew will encounter the most harmful radiation environment in transit to Mars from which they must be adequately protected. However, once on the planet's surface, the Martian environment should provide a significant amount of protection from free-space radiative fluxes. In current Mars scenario descriptions, the crew flight time to Mars is estimated to be anywhere from 7 months to over a year each way, with stay times on the surface ranging from 20 days to 2 years. To maintain dose levels below established astronaut limits, dose estimates need to be determined for the entire mission length. With extended crew durations on the surface anticipated, the characterization of the Mars radiation environment is important in assessing all radiation protection requirements. This synopsis focuses on the probable doses incurred by surface inhabitants from the transport of galactic cosmic rays and solar protons through the Mars atmosphere.

Astronauts↗
PubMed2006

Does Enceladus govern magnetospheric dynamics at Saturn?

Instruments on the Cassini spacecraft reveal that a heat source within Saturn's moon Enceladus powers a great plume of water ice particles and dust grains, a geyser that jets outward from the south polar regions and most likely serves as the dominant source of Saturn's E ring. The interaction of flowing magnetospheric plasma with the plume modifies the particle and field environment of Enceladus. The structure of Saturn's magnetosphere, the extended region of space threaded by magnetic-field lines linked to the planet, is shaped by the ion source at Enceladus, and magnetospheric dynamics may be affected by the rate at which fresh ions are created.

Atmosphere↗
PubMed2003

Solar UV irradiation conditions on the surface of Mars.

The UV radiation environment on planetary surfaces and within atmospheres is of importance in a wide range of scientific disciplines. Solar UV radiation is a driving force of chemical and organic evolution and serves also as a constraint in biological evolution. In this work we modeled the transmission of present and early solar UV radiation from 200 to 400 nm through the present-day and early (3.5 Gyr ago) Martian atmosphere for a variety of possible cases, including dust loading, observed and modeled O3 concentrations. The UV stress on microorganisms and/or molecules essential for life was estimated by using DNA damaging effects (specifically bacteriophage T7 killing and uracil dimerization) for various irradiation conditions on the present and ancient Martian surface. Our study suggests that the UV irradiance on the early Martian surface 3.5 Gyr ago may have been comparable with that of present-day Earth, and though the current Martian UV environment is still quite severe from a biological viewpoint, we show that substantial protection can still be afforded under dust and ice.

Bacteriophage T7↗
PubMed1980

Anaerobic microbiology in the NASA space program.

After briefly reviewing the earlier methods used to monitor the microbial load of returned lunar material, the author reports the more accurate research on the ability of terrestrial organisms to grow under simulated Martian environments. The possible importance of anaerobic microbiology can readily be seen because of the low level of O2 found on Mars. The question of whether any of the experiments on board the Viking landers show any indication of life on Mars is discussed in detail.

Anaerobiosis↗
PubMed1986

Dosimetric mapping inside BIORACK.

The experiment was flown in different locations inside BIORACK on the D1 mission. It contained different plastic detectors (cellulose nitrate, Lexan, and CR 39) and emulsions to measure the high LET components of the radiation environment. For low LET measurements thermoluminescence dosimeters (LiF) were used. The paper gives data about total dose, charge, energy, and LET spectra so far obtained. These data are compared with data of previous spaceflights.

Cosmic Radiation↗
PubMed1989

Radiation hazards on space missions outside the magnetosphere.

Future space missions outside the magnetosphere will subject astronauts to a hostile and unfamiliar radiation environment. An annual dose equivalent to the blood-forming organs (BFOs) of approximately 0.5 Sv is expected, mostly from heavy ions in the galactic cosmic radiation. On long-duration missions, an anomalously-large solar energetic particle event may occur. Such an event can expose astronauts to up to approximately 25 Gy (skin dose) and up to approximately 2 Sv (BFO dose) with no shielding. The anticipated radiation exposure may necessitate spacecraft design concessions and some restriction of mission activities. In this paper we discuss our model calculations of radiation doses in several exo-magnetospheric environments. Specific radiation shielding strategies are discussed. A new calculation of aluminum equivalents of potential spacecraft shielding materials demonstrates the importance of low-atomic-mass species for protection from galactic cosmic radiation.

Aluminum↗
PubMed1998

Testing and evaluation for astronaut extravehicular activity (EVA) operability.

Because it is the human component that defines space mission success, careful planning is required to ensure that hardware can be operated and maintained by crews on-orbit. Several methods exist to allow researchers and designers to better predict how hardware designs will behave under the harsh environment of low Earth orbit, and whether designs incorporate the necessary features for Extra Vehicular Activity (EVA) operability. Testing under conditions of simulated microgravity can occur during the design concept phase when verifying design operability, during mission training, or concurrently with on-orbit mission operations. The bulk of testing is focused on normal operations, but also includes evaluation of credible mission contingencies or "what would happen if" planning. The astronauts and cosmonauts who fly these space missions are well prepared and trained to survive and be productive in Earth's orbit. The engineers, designers, and training crews involved in space missions subject themselves to Earth based simulation techniques that also expose them to extreme environments. Aircraft falling ten thousand feet, alternating g-loads, underwater testing at 45 foot depth, enclosure in a vacuum chamber and subject to thermal extremes, each carries with it inherent risks to the humans preparing for space missions.

Astronauts↗
PubMedDate not supplied

[Problems of anesthesia, surgical care and resuscitation during manned space flights].

When exploring the problems of medical aid to be rendered in manned space flights, it is necessary to take into consideration the specific features of the environment as well as the changes in the human body induced by space flight effects. In space flight anesthesia can be applied using such advanced methods as multi-component balanced anesthesia and peridural anesthesia. Surgery and resuscitation can be performed, employing the procedures and methods that allow operations in an abacterial environment, correction of vital dysfunctions with the aid of artificial pulmonary ventilation, cardiac electrotherapy, and sorptive purification of body fluids. Various aspects of infusion treatment and first medical aid are discussed.

Anesthesia↗
PubMed2001

Organics produced by ion irradiation of ices: some recent results.

Some results, recently obtained from laboratory experiments of ion irradiation of ice mixtures containing H, C, N, and O, are here summarized. They are relevant to the formation and evolution of complex organics on interstellar dust, comets and other small bodies in the external Solar System. In particular the formation of CN-bearing species is discussed. Interstellar dust incorporated into primitive Solar System bodies and subsequently delivered to the early Earth, may have contributed to the origin of life. The delivery of CN-bearing species seems to have been necessary because molecules containing the cyanogen bond are difficult to be produced in an environment that is not strongly reducing as that of the early Earth probably was. Moreover we report on an ongoing research program concerning the interaction between refractory materials produced by ion irradiation of simple ices and biological materials (amino acids, proteins, cells).

Argon↗
PubMed2005

Men and women in space.

The influence of gender on the social context in which work performance takes place is considered. Women in single and mixed-gender polar expedition groups reported concern for the welfare of a teammate as a significant stressor. All-male teams exhibited higher levels of competitiveness and a lesser tendency to talk about their feelings. Excerpts from expedition debriefing interviews illustrate gender-related patterns noted in extreme environments. Application of these findings for the better selection, training, and performance of mixed-gender space crews is examined. A case study approach to conducting research on crew performance is recommended, and strategies for dealing with confidentiality are discussed.

Adaptation, Psychological↗
PubMed1998

Observation of indigenous polycyclic aromatic hydrocarbons in 'giant' carbonaceous antarctic micrometeorites.

Two-step laser desorption/laser ionization mass spectrometry (microL2 MS) was used to establish the nature and mass distribution of polycyclic aromatic hydrocarbons (PAHs) in fragments of fifteen 'giant' (approximately 200 microns) carbonaceous Antarctic micrometeorites (AMMs). Detectable concentrations of PAHs were observed in all AMMs showing a fine-grained matrix. The range of integrated PAH signal intensities varied between samples by over two orders of magnitude. No evidence of contamination whilst in the Antarctic environment could be found. The dramatic variation of both PAH signal intensities and mass distributions between AMMs along with comprehensive contamination checks demonstrates that particles are not exposed to terrestrial PAHs at or above detection limits, either subsequent, during or prior to collection. Comparison of the observed PAH distributions with those measured in three carbonaceous chondrites [Orgueil (CI1), Murchison (CM2) and Allende (CV3)] under identical conditions demonstrated that marked differences exist in the trace organic composition of these two sources of extraterrestrial matter. In general, AMMs show a far richer distribution of unalkylated 'parent' PAHs with more extended alkylation series (replacement of -H with -(CH2)n-H; n = 1, 2, 3 ...). The degree of alkylation loosely correlates with a metamorphic index that represents the extent of frictional heating incurred during atmospheric entry. A search for possible effects of the chemical composition of the fine-grain matrix of host particles on the observed PAH distributions reveals that high degrees of alkylation are associated with high Na/Si ratios. These results, in addition to other observations by Maurette, indicate that 'giant' micrometeorites survive hypervelocity (> or = 11 km s-1) atmospheric entry unexpectedly well. Because such micrometeorites are believed to represent the dominant mass fraction of extraterrestrial material accreted by the Earth, they may have played a significant role in the prebiotic chemical evolution of the early Earth through the delivery of complex organic matter to the surface of the planet.

Antarctic Regions↗
PubMed1991

Urey Prize Lecture: Planetary Evolution and the Origin of Life.

The origin of life appears to be closely tied to the formation and early evolution of the solar system. Key questions deal with the source of abiotic organic material on the early Earth, the nature of interstellar organic material and its relationship to the observed organic compounds in the outer solar system, and the possible origin of life on Mars early in its history. From the perspective of planetary environments, liquid water is the essential requirement for life and serves as a surrogate indicator for life. New models and analyses in conjunction with data returned from upcoming missions promise to significantly advance our knowledge of how life originated in our solar system.

Awards and Prizes↗
PubMed2001

Estimation of neutron and other radiation exposure components in low earth orbit.

The interaction of high-energy space radiation with spacecraft materials generates a host of secondary particles, some, such as neutrons, are more biologically damaging and penetrating than the original primary particles. Before committing astronauts to long term exposure in such high radiation environments, a quantitative understanding of the exposure and estimates of the associated risks are required. Energetic neutrons are traditionally difficult to measure due to their neutral charge. Measurement methods have been limited by mass and weight requirements in space to nuclear emulsion, activation foils, a limited number of Bonner spheres, and TEPCs. Such measurements have had limited success in quantifying the neutron component relative to the charged components. We will show that a combination of computational models and experimental measurements can be used as a quantitative tool to evaluate the radiation environment within the Shuttle, including neutrons. Comparisons with space measurements are made with special emphasis on neutron sensitive and insensitive devices.

Astronauts↗