Meteoritics and mineralogy on possible ancient Martian life]

Possible relic biogenic activity in martian meteorite ALH84001 was proposed by McKay et al. (Science, 273, 924-930, 1996). This ancient meteorite of 4.5 billion years old contains abundant carbonates as secondary minerals precipitated from a fluid on the martian surface. They showed the following lines of evidence for the ancient life; (1) unique mineral compositions and biominerals, (2) polycyclic aromatic hydrocarbons (PAHs) in association with the carbonates, and (3) unique structures and morphologies typical of nanobacteria or microfossils. This review is divided into two parts; one is on the martian meteorites in general and ALH84001, which has many features unlike other martian meteorites, and the other is on mineralogical (biomineralogical) and geochemical features of the carbonates and microfossil-like structures. There is little doubt that ALH84001 is from Mars as well as eleven other SNC meteorites. However, the mineralogical and biomineralogical evidence for martian bacteria given by McKay et al. (1996) is controversial, and could be formed by non-biogenic processes. Thus, further study of ALH84001 and other martian meteorites is required. We also need to consider the future Mars mission especially sample return mission.     

Pros and cons for Martian life: scientific debate on ALH84001]

Scientific debate related to possible martian life is summarized in this article. Even there is no firm conclusion yet to convince the existence of life on Mars, intensive studies on the meteorite ALH84001 have invoked many valuable findings.     

Martian channels and the search for extraterrestrial life

Summary The origin of the channels on Mars has been a subject of intense interest since they were first recognized on early Mariner 9 images (Driscoll, 1972; Masursky, 1973). Their presence on the planet, and their striking resemblance to terrestrial flood channels related to glacial outbursts or to dendritic river systems has suggested to most investigators (Baker, 1974, 1977; Nummedal, 1978; Carr, 1979; Masursky et al., 1977) that they were formed by running water. Because life as we know it is dependent on water, the discovery by the Mariner cameras, of watercut channels and volcanoes as a source for water, and water ice in the residual north polar cap by Viking, has reaffirmed the choice of Mars as the best target for the search for extraterrestrial life.     

Survival of microorganisms in a simulated Martian environment

Studies were conducted to determine the effects of a simulated Martian environment on the survival of terrestrial microorganisms. Mariner IV data were utilized to establish the Martian model. Day/night cycling, temperature, humidity, pressure, atmospheric constituents and solar irradiation were controlled in a 3600 ft³ simulation chamber at the Boeing Kent Space Simulation Laboratory.Microorganisms used in this study included suspensions of:Bacillus subtilis var.niger spores, a psychrophilic sporeformer, and the organisms contained in a soil emulsion prepared from several soils. Aliquots of each suspension were placed on separate sterile stainless steel planchets, air dried, and positioned in 4 layers in sterile limonite. One-half of the samples placed on the surface received the total solar spectrum (0.44 earth solar constants); the remainder of the surface samples received the above treatment minus the ultraviolet (UV) portion of the spectrum. Subsurface samples were placed in limonite at depths of 0.5, 1.5 and 3 in.Survival data were obtained for chamber exposure periods of 2, 4, and 8 days. These data indicate that: (1) organisms exposed to the total solar spectrum did not survive, (2) a time dependent, 1 to 3 log, reduction in numbers occurred in the surface samples that received the solar spectrum minus UV, and (3) subsurface survival varied with depth and type or organism.     

Response of terrestrial microorganisms to a simulated Martian environment

Soil samples from Cape Canaveral were subjected to a simulated Martian environment and assayed periodically over 45 days to determine the effect of various environmental parameters on bacterial populations. The simulated environment was based on the most recent available data, prior to the Viking spacecraft, describing Martian conditions and consisted of a pressure of 7 millibars, an atmosphere of 99.9% CO2 and 0.1% O2, a freeze-thaw cycle of -65 degrees C for 16 h and 24 degrees C for 8 h, and variable moisture and nutrients. Reduced pressure had a significant effect, reducing growth under these conditions. Slight variations in gaseous composition of the simulated atmosphere had negligible effect on growth. The freeze-thaw cycle did not inhibit growth but did result in a slower rate of decline after growth had occurred. Dry samples exhibited no change during the 45-day experiment, indicating that the simulated Martian environment was not toxic to bacterial populations. Psychotrophic organisms responded more favorably to this environment than mesophiles, although both types exhibited increases of approximately 3 logs in 7 to 14 days when moisture and nutrients were available.     

Response of terrestrial microorganisms to a simulated Martian environment.

Soil samples from Cape Canaveral were subjected to a simulated Martian environment and assayed periodically over 45 days to determine the effect of various environmental parameters on bacterial populations. The simulated environment was based on the most recent available data, prior to the Viking spacecraft, describing Martian conditions and consisted of a pressure of 7 millibars, an atmosphere of 99.9% CO2 and 0.1% O2, a freeze-thaw cycle of -65 degrees C for 16 h and 24 degrees C for 8 h, and variable moisture and nutrients. Reduced pressure had a significant effect, reducing growth under these conditions. Slight variations in gaseous composition of the simulated atmosphere had negligible effect on growth. The freeze-thaw cycle did not inhibit growth but did result in a slower rate of decline after growth had occurred. Dry samples exhibited no change during the 45-day experiment, indicating that the simulated Martian environment was not toxic to bacterial populations. Psychotrophic organisms responded more favorably to this environment than mesophiles, although both types exhibited increases of approximately 3 logs in 7 to 14 days when moisture and nutrients were available.     

The early life environment and the epigenome

Several lines of evidence point to the early origin of adult onset disease. A key question is: what are the mechanisms that mediate the effects of the early environment on our health? Another important question is: what is the impact of the environment during adulthood and how reversible are the effects of early life later in life? The genome is programmed by the epigenome, which is comprised of chromatin, a covalent modification of DNA by methylation and noncoding RNAs. The epigenome is sculpted during gestation, resulting in the diversity of gene expression programs in the distinct cell types of the organism. Recent data suggest that epigenetic programming of gene expression profiles is sensitive to the early-life environment and that both the chemical and social environment early in life could affect the manner by which the genome is programmed by the epigenome. We propose that epigenetic alterations early in life can have a life-long lasting impact on gene expression and thus on the phenotype, including susceptibility to disease. We will discuss data from animal models as well as recent data from human studies supporting the hypothesis that early life social-adversity leaves its marks on our epigenome and affects stress responsivity, health, and mental health later in life.     

Early life environment and snoring in adulthood

Background

To our knowledge, no studies of the possible association of early life environment with snoring in adulthood have been published. We aimed to investigate whether early life environment is associated with snoring later in life.

Methods

A questionnaire including snoring frequency in adulthood and environmental factors in early life was obtained from 16,190 randomly selected men and women, aged 25–54 years, in Sweden, Norway, Iceland, Denmark and Estonia (response rate 74%).

Results

A total of 15,556 subjects answered the questions on snoring. Habitual snoring, defined as loud and disturbing snoring at least 3 nights a week, was reported by 18%. Being hospitalized for a respiratory infection before the age of two years (adjusted odds ratio (OR) = 1.27; 95% confidence interval (CI) 1.01–1.59), suffering from recurrent otitis as a child (OR = 1.18; 95%CI 1.05–1.33), growing up in a large family (OR = 1.04; 95%CI 1.002–1.07) and being exposed to a dog at home as a newborn (OR = 1.26; 95%CI 1.12–1.42) were independently related to snoring later in life and independent of a number of possible confounders in adulthood. The same childhood environmental factors except household size were also related with snoring and daytime sleepiness combined.

Conclusion

The predisposition for adult snoring may be partly established early in life. Having had severe airway infections or recurrent otitis in childhood, being exposed to a dog as a newborn and growing up in a large family are environmental factors associated with snoring in adulthood.     

The early life social environment and DNA methylation

Although epidemiological data provides evidence that there is an interaction between genetics (nature) and the social and physical environments (nurture) in human development; the main open question remains the mechanism. The pattern of distribution of methyl groups in DNA is different from cell-type to cell type and is conferring cell specific identity on DNA during cellular differentiation and organogenesis. This is an innate and highly programmed process. However, recent data suggests that DNA methylation is not only involved in cellular differentiation but that it is also involved in modulation of genome function in response to signals from the physical, biological and social environments. We propose that modulation of DNA methylation in response to environmental cues early in life serves as a mechanism of life-long genome "adaptation" that molecularly embeds the early experiences of a child ("nurture") in the genome ("nature"). There is an emerging line of data supporting this hypothesis in rodents, non-human primates and humans that will be reviewed here. However, several critical questions remain including the identification of mechanisms that transmit the signals from the social environment to the DNA methylation/demethylation enzymes.     

Adipose tissue development--impact of the early life environment

Increasing experimental and observational evidence in both animals and humans suggests that early life events are important in setting later fat mass. This includes both the number of adipocytes and the relative distribution of both brown and white adipose tissue. Brown adipose tissue is characterised as possessing a unique uncoupling protein (UCP)1 which enables the rapid generation of large amounts of heat and is most abundant in the newborn. In large mammals such as sheep and humans, brown fat that is located around the major internal organs, is largely lost during the postnatal period. However, it is retained in small and discrete areas into adulthood when it is sensitive to environmental cues such as changes in ambient temperature or day length. The extent to which brown adipose tissue is lost or replaced by white adipose tissue and/or undergoes a process of transdifferentiation remains controversial. Small amounts of UCP1 can also be present in skeletal muscle which now appears to share the same common precursor cell as brown adipose tissue. The functional consequences of UCP1 in muscle remain to be confirmed but it could contribute to dietary induced thermogenesis. Challenges in elucidating the primary mechanisms regulating adipose tissue development include changes in methylation status of key genes during development in different species, strains and adipose depots. A greater understanding of the mechanisms by which early life events regulate adipose tissue distribution in young offspring are likely to provide important insights for novel interventions that may prevent excess adiposity in later life.     

Thermophiles and life science in space]

Thermophiles are microorganisms that can grow at temperatures higher than 50 or 60 degrees C. There are thermophilic eubacteria and thermophilic archaebacteria. Thermophilic microorganisms can be found geothermally and hydrothermally active area. The water penetrates into deep subsurface around thermal area and reacts with hot basalt. Some of the compounds in the water are reduced by the reaction. The water returned to the surface and reacts with seawater or air, depending on the location of the thermal area. Many types of autotrophes and heterotrophes were found near thermally active area. The microorganisms form the ecosystem based on the redox chemical reactions. All of the structural elements in thermophilic microorganisms are thermophilic or thermostable. Proteins found in microorganisms are thermostable. Though several common characteristics can be found in thermostable proteins, it is not easy to attribute the stability to specific amino acid residues. DNA in thermophiles is stabilized by increasing the G+C content or by histone-like DNA binding proteins. There are several molecular biological and geological evidences to support the relation between ancient life forms and thermal activity on the Earth. Thermophiles of different life forms may be found in thermally active area, in such as those that may be present in satellites of Jupiter.     

The biennial life strategy in a random environment

A discrete-time population model with two age classes is studied which describes the growth of biennial plants in a randomly varying environment. A fraction of the oldest age class delays its flowering each year. The solution of the model involves products of random matrices. We calculate the exact mean and variance of the long-run geometric growth rate assuming a gamma distribution for the random number of offspring per flowering plant after one year. It is shown, both by analytical calculation and numerical examples, that it is profitable for the population to delay its flowering, in the sense that the average growth rate increases and the extinction probability decreases. The optimal values of the flowering fraction depend upon the environmental and model parameters.     

The biennial life strategy in a random environment

In a previous paper (J. Math. Biol. 26, 199–215 (1988)) we calculated the mean and variance of the long-run geometric growth rate of a discrete-time population model with two age classes in a random environment. The formula which was used in that paper as the starting point for the computation of the variance represents only the contribution of the one-period variances. Here we supplement these results by a calculation of the exact variance. All qualitative conclusions reached before are unaffected.     

Martian paleolakes and waterways: Exobiological implications

The problems of how warm and wet Mars once was and when climate transitions may have occurred are not well understood. Mars may have had an early environment similar to Earth's that was conductive to the ermergence of life. In addition, increasing geologic evidence indicates that water, upon which terrestrial life depends, has been present on Mars throughout its history. This evidence suggests that life could have developed not only on early Mars but also over longer periods of time in longer lasting, more clement local environments. Indications of past or present life most likely would be found in areas where liquid water existed in sufficient quantities to provide for the needs of biological systems. We suggest that paleolakes may have provided such environments. Unlike the case on Earth, this record of the origin and evolution of life has probably not been erased by extensive deformation of the Martian surface. Our work has identified eleven prospective areas where large lacustrine basins may once have existed. These areas are important for future biological, geological, and climatological investigations.Presented at the International Symposium on The Biological Exploration of Mars, October 26–27, 1990, Tallahassee, FL, U.S.A.     

Boron Enrichment in Martian Clay

We have detected a concentration of boron in martian clay far in excess of that in any previously reported extra-terrestrial object. This enrichment indicates that the chemistry necessary for the formation of ribose, a key component of RNA, could have existed on Mars since the formation of early clay deposits, contemporary to the emergence of life on Earth. Given the greater similarity of Earth and Mars early in their geological history, and the extensive disruption of Earth''s earliest mineralogy by plate tectonics, we suggest that the conditions for prebiotic ribose synthesis may be better understood by further Mars exploration.     

On the boundary between economy and environment in life cycle assessment

Purpose

We investigate how the boundary between product systems and their environment has been delineated in life cycle assessment and question the usefulness and ontological relevance of a strict division between the two.

Methods

We consider flows, activities and impacts as general terms applicable to both product systems and their environment and propose that the ontologically relevant boundary is between the flows that are modelled as inputs to other activities (economic or environmental)—and the flows that—in a specific study—are regarded as final impacts, in the sense that no further feedback into the product system is considered before these impacts are applied in decision-making. Using this conceptual model, we contrast the traditional mathematical calculation of the life cycle impacts with a new, simpler computational structure where the life cycle impacts are calculated directly as part of the Leontief inverse, treating product flows and environmental flows in parallel, without the need to consider any boundary between economic and environmental activities.

Results and discussion

Our theoretical outline and the numerical example demonstrate that the distinctions and boundaries between product systems and their environment are unnecessary and in some cases obstructive from the perspective of impact assessment, and can therefore be ignored or chosen freely to reflect meaningful distinctions of specific life cycle assessment (LCA) studies. We show that our proposed computational structure is backwards compatible with the current practice of LCA modelling, while allowing inclusion of feedback loops both from the environment to the economy and internally between different impact categories in the impact assessment.

Conclusions

Our proposed computational structure for LCA facilitates consistent, explicit and transparent modelling of the feedback loops between environment and the economy and between different environmental mechanisms. The explicit and transparent modelling, combining economic and environmental information in a common computational structure, facilitates data exchange and re-use between different academic fields.

     

Integration of working environment into life cycle assessment framework

Background, aim, and scope  Life cycle assessment (LCA) has been considered one of the tools for supporting decision-making related to the environmental aspects of a product system. It has mainly been used to evaluate the potential impacts associated with relevant inputs and outputs to/from a given product system throughout its life cycle. In most cases, LCA has not considered the impacts on the internal environment, i.e. working environment, but only the external environment. Recently, it has been recognized that the consideration of the impacts on the working environment as well as on the external environment, is needed in order to assess all aspects of the effects on human well-being. To this end, this study has developed a total environmental assessment methodology which enables one to integrate both the working environment and the external environment into the conventional LCA framework. Materials and methods  In general, the characteristics of the impacts on the external environment are different from those on the working environment. In order to properly integrate the two types into total environmental impacts, it is necessary to define identical system boundaries and select impact category indicators at the same level. In order to define the identical system boundary and reduce the uncertainties of LCI results, the hybrid IOA (input–output analysis) method, which integrates the advantages between conventional LCI method and IOA method, is introduced to collect input and output data throughout the entire life cycle of a given product. For the impact category indicators at the endpoint level, LWD (Lost Work Days) is employed to evaluate the damage to human health and safety in the working environment, while DALY (disability-adjusted life years) and PAF (Potentially Affected Fraction) are selected to evaluate the damage to human health and eco-system quality in the external environment, respectively. Results and discussion  The environmental intervention factors (EIFs) are developed not only for the data categories of resource use, air emissions, and water emissions, but also for occupational health and safety to complete a life cycle inventory table. For the development of the EIFs on occupational health and safety, in particular, the number of workers affected by i hazardous items and the number of workers affected at the i magnitude of disability are collected. For the characterization of the impact categories in the working environment, such as occupational health and safety, the exposure factors, effect factors, and damage factors are developed to calculate the LWD of each category. For normalization, the normalization reference is defined as the total LWD divided by the total number of workers. A case study is presented to illustrate the applicability of the proposed method for the integration of the working environment into the conventional LCA framework. Conclusions  This study is intended to develop a methodology which enables one to integrate the working environmental module into the conventional LCA framework. The hybrid IOA method is utilized to extend the system boundary of both the working environment module and the external environment module to the entire life cycle of a product system. In this study, characterization models and category indicators for occupational health and safety are proposed, respectively, while the methodology of Eco-indicator 99 is used for the external environment. In addition to aid further understanding on the results of this method, this study introduced and developed the category indicators such as DALY, and LWD, which can be expressed as a function of time, and introduced PAF, which can be expressed as a probability. Recommendations and perspectives  The consideration of the impacts not only on the external environment, but also on the working environment, is very important, because the best solution for the external environment may not necessarily be the best solution for the working environment. It is expected that the integration of occupational health and safety matters into the conventional LCA framework can bring many benefits to individuals, as well as industrial companies, by avoiding duplicated measures and false optimization.