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PubMedDate not supplied

[Dr. Tadeusz Rakowiecki (July 26, 1878-April 6, 1965), physician, astronomer and writer--on the 25th anniversary of his death].

He decided to study medicine to be self-reliant and helpful for the society though he showed outstanding abilities to exact sciences, in particular mathematics. He was graduated at the Warsaw University in 1903 "cum eximia laude" in medicine. Apart from medicine he had disclosed interest in literature that was realized by many lectures and publications related to the famous and outstanding Polish writer Stefan Zeromski. Since 1930 Dr. Rakowiecki has started as self-taught astronomy studies becoming soon one of seven most eminent Polish astronomers. In the thirties there appeared his two-volume monography entitled "Drogi Planet i Komet" ("Motions of planets and comets") that has become the first fundamental Polish handbook of astronomy actual up to seventies. His scientific achievements based on higher mathematics included 20 important reports on astronomy and several monographs on mathematics. In 1930 he had refused several proposals to head University Chairs of Astronomy, among others in Lwów, due to modesty and his willingness to help and to serve his patients. He had been a demon for work, his rest after admission of patients were astronomy calculations, while when tired with the latters he became occupied with medicine.

Astronomy↗
PubMed1988

The effects of gravitational forces on reproduction and development.

It is clear that increased gravitational forces can affect biologic reproduction and development, although exact mechanisms of action have not been established. Except for three studies of male pilot and astronaut fertility, human reproduction and development studies of chronic or acute exposure to micro- or hypergravity environments have not been carried out. Only two reproduction and development studies (both Soviet) have been done under chronic or acute exposure to microgravity. It is unlikely that chronic human exposure to hypergravity will occur except when planets much larger than Earth are colonized. Colonies dependent on reproduction for continued existence probably could not be established on planets with masses significantly dissimilar to Earth because hypergravity or hypogravity are likely to affect reproduction adversely and cause abnormal growth and development. Acute exposures to gravitational changes in the later stages of development appear to be less detrimental, but much remains to be discovered about how gravity affects reproduction and development of mammals, humans in particular. Earth's gravitational force has helped to shape human reproduction and development. Only when the limits of mammalian biology on both sides of 1 g are explored will we be able to determine the extent to which gravity determines biologic structure and function.

Animals↗
PubMed1987

Some effects of the force environment on the heart, lungs and circulation.

The data obtained in a series of human and animal experiments carried out during the last 45 years in centrifuges, specially instrumented dive bombers, and during changes in body position are the major bases for this paper. The integrated and highly effective cardiovascular reflexes which allow awake, upright humans to regain and/or maintain vision and consciousness during sustained inertial force environments several times greater than at the surface of planet Earth are particularly impressive. Multiplication of vertical gradients in interserosal pericardial, pleural, abdominal and cerebrospinal fluid pressures and/or forces in proportion, and in the resultant vectorial direction of the force environment play a critical role in this capability both in aerospace flight and everyday life on planet Earth. The differences between the near zero specific gravity of intra-alveolar gas and the (about) 1.05 value for the encompassing blood and tissue, render lung function highly susceptible to the weight determinant force environment. Creation of a womb-like environment by liquid whole-body immersion plus assisted breathing of a respirable liquid, both with specific gravities closely similar to bodily tissues, is a seemingly impractical but technologically and biologically documented expedient for allowing air breathers to endure very high sustained force and pressure environments.

Aerospace Medicine↗
PubMedDate not supplied

[Weltanschauung aspects of the problem of man, the biosphere and space].

The paper discusses philosophic approaches to the problem of man-environment interplay. Many important problems humanity faces today are associated with biology. Biomedical and astrophysical studies are being carried out to gain a better insight into the laws governing evolution and further development of the Universe. The emergence of a human society started a qualitatively new stage in the evolution of organic matter. A rapid progress of science and engineering is accompanied by a significant rearrangement of the natural environment and, particularly, of living beings. The biosphere is transforming into the sphere of intelligence, i.e. noosphere. However, natural phenomena are still more powerful than man-made productive forces. Man's excursion into outer space allowed him to look at himself as if from the outside and to evaluate critically his actual role, position and responsibility in the infinite Universe as compared with other forms of life and intelligence. The Universe may be boundlessly great but for human beings there is nothing better than the Earth. Our planet will long remain the base for the existence and development of humanity. Today man ought to take the streering-wheel of evolution and fate of the biosphere into his hands, in order to preserve, through the efforts of many generations, our planet as the gem of the Universe.

Biological Evolution↗
PubMed1982

Population, environment, medicine and global sustainability.

The final two decades of this century see our planet in a highly perilous condition. This paper, after touching on the problem of nuclear proliferation, goes on to consider three other issues overpopulation, environmental depredation and the future of medical practice all of which are of high salience. The section on population concentrates on the time required for numbers to stabilize at two children per family. Europe is likely to attain stabilization before 2050, North America and the USSR by 2100. In the developing world South and East Asia could also be in balance by the beginning of the twenty-second century; but the situation in Africa vis-à-vis population growth is much more serious and stabilization cannot be anticipated until about 2150. Destruction of life support systems on a massive scale continues, particularly in developing countries. Much of Asia, Africa and Latin America is riddled with soil erosion; expanding populations of humans and livestock are proving a notable catalyst to desertification; the 'firewood crisis' is deepening as slowly but surely the earth is being deforested. There is little convincing evidence that the major aims of the World Conservation Strategy maintenance and responsible utilization of essential ecological systems, preservation of genetic diversity are being obeyed anywhere in the world. In the more sustainable society of the future engineering medicine with its proclivity for resource depletion will be less attractive. Rather will the emphasis be on prevention and on attempting to delineate the environmental factors known to be responsible for an increasing number of diseases. The likely pattern of morbidity and mortality in the twenty-first century is discussed. Geriatric medicine will hold pride of place; the incidence of cancer will rise markedly, and as an increasing number of Third World nations undergo the process of development diseases, which up till now have mainly affected affluent technological societies, it will spread throughout the planet.

Africa↗
PubMed1994

Role of alkali cations (K+ and Na+) in cyanobacterial nitrogen fixation and adaptation to salinity and osmotic stress.

Cyanobacteria occupy almost every possible ecological niche on earth, being tolerant to a large number of environmental stresses, including salinity and drought. Many of them also fix atmospheric nitrogen. They are responsible for a significant share of biosolar energy conversions on this planet and make substantial contributions to the carbon and nitrogen status of both oceans and soils. Sodium and potassium are two of the most prevalent cations on this planet. While K+ is an essential macronutrient in most life-forms, Na+ is strongly discriminated by means of highly selective alkali cation transport systems, favouring K+ over Na+. Although a nutritional requirement for K+ has not been specifically investigated, rapid accumulation of K+ during salt/osmotic stress has been observed in several cyanobacteria. Genes and proteins constituting a membrane-bound, turgor- and osmo-inducible, Kdp-ATPase-like system in Anabaena strains that may help in their early K+ responses to salt/osmotic stress have been identified. An unusual, specific and absolute requirement for trace quantities of sodium has been documented in cyanobacteria. Work done in our laboratory, and elsewhere, has elucidated the mechanisms underlying such a unique requirement. It has long been believed that cyanobacteria scavenge and immobilise sodium. We have, however, shown that sodium exclusion brought about by curtailment of influx and active efflux of Na+ forms the basis of salt tolerance in these microbes and that the inherent salt tolerance can be modified by factors that modulate Na+ fluxes in cyanobacteria. Identification of genes affecting the cation relationships in nitrogen-fixing cyanobacteria is currently in progress.

Adaptation, Physiological↗
PubMed1997

Analogs of the early solar system.

Within the last few decades, the existence of protoplanetary disks has been inferred on the basis of emission from T Tauri stars that does not arise from a stellar photosphere. More recently, high-resolution interferometric techniques have resolved the dust continuum emission, and millimeter arrays have imaged circumstellar molecular gas. These measurements corroborate the disk interpretation; many T Tauri stars are surrounded by centrifugally supported circumstellar disks with radial sizes of order 100 AU. Further proof issues from Hubble Space Telescope images of disks that are illuminated externally. The morphology of circumstellar dust is revealed in striking detail and affirms the prevalence and dimensions of disks imaged at longer wavelengths. The fate of circumstellar material around young stars must be understood in order to discern the degree to which these disks are proto-planetary. Observational studies of circumstellar disks which are in the beginning of a dispersal phase are challenging and place great demands on astronomical techniques. Nevertheless, the connection between disks and the formation of extra-solar planets is supported by increasing circumstantial evidence. Optically thin dust continuum emission persists in T Tauri stars and is detected around some young main sequence stars. Since the dust is subject to rapid dispersal by radiation pressure and Poynting-Robertson drag, some mechanism of replenishment is required. Disks around nearby young main sequence stars show evidence for inner voids and disk asymmetries that should also disappear on short timescales. The presence of large orbiting bodies which collide and interact with the resulting debris can explain both the persistence of optically thin dust and the maintenance of otherwise-ephemeral dynamical features. Together with recent detections of extra-solar planets, these observations lend some support to the hypothesis that circumstellar disks commonly give birth to planetary systems.

Astronomy↗
PubMed1998

The Quantum Event of Oceanic Crustal Accretion: Impacts of Diking at Mid-Ocean Ridges

Seafloor diking-eruptive events represent the irreducible, quantum events of upper oceanic crustal accretion. They record events by which a large portion of the oceanic crust has formed through geological history. Since 1993, the U.S. Navy's real-time Sound Surveillance System has allowed location of ongoing acoustic signatures of dike emplacement and basalt eruptions at ridge crests in the northeast Pacific. These diking-eruptive events trigger a sequence of related, rapidly evolving physical, chemical, and biological processes. Magmatic volatiles released during these events may provide nutrients for communities of subseafloor microorganisms, some of which thrive in high-temperature anaerobic environments. Many of the organisms identified from these systems are Archaea. If microorganisms can thrive in the water-saturated pores and cracks within deep, volcanically active portions of our planet, other hydrothermally active planets may harbor similar life forms.

Journal Article↗
PubMed2006

The asteroid and comet impact hazard: risk assessment and mitigation options.

The impact of extraterrestrial matter onto Earth is a continuous process. On average, some 50,000 tons of dust are delivered to our planet every year. While objects smaller than about 30 m mainly disintegrate in the Earth's atmosphere, larger ones can penetrate through it and cause damage on the ground. When an object of hundreds of meters in diameter impacts an ocean, a tsunami is created that can devastate coastal cities. Further, if a km-sized object hit the Earth it would cause a global catastrophe due to the transport of enormous amounts of dust and vapour into the atmosphere resulting in a change in the Earth's climate. This article gives an overview of the near-Earth asteroid and comet (near-Earth object-NEO) impact hazard and the NEO search programmes which are gathering important data on these objects. It also points out options for impact hazard mitigation by using deflection systems. It further discusses the critical constraints for NEO deflection strategies and systems as well as mitigation and evacuation costs and benefits. Recommendations are given for future activities to solve the NEO impact hazard problem.

Climate↗
PubMed1990

Xenon fractionation in porous planetesimals.

The distinctively fractionated Xe on Mars and Earth may have its root in a common source from which both planets accreted. We begin with Ozima and Nakazawa's hypothesis that terrestrial Xe fractionation was caused by gravitational separation of adsorbed solar nebular gases inside large porous planetesimals. We point out that Xe would have been trapped as the planetesimal grew and pores were squeezed shut by lithostatic pressure. We show that enough fractionated Xe to supply the Earth could have been trapped this way. The degree of fractionation is controlled by the lithostatic pressure at the pore-closing front and so would have been roughly the same for all large planetesimals. The predicted degree of fractionation agrees well with that preserved in terrestrial and martian Xe. Relative to Xe, this source is strongly depleted in other noble gases. In contrast to the original Ozima and Nakazawa hypothesis, our hypothesis predicts the observed fractionation, and it allows planetary accretion to occur after the dissipation of the solar nebula. The required planetesimals are large, representing a class of object now extinct in the solar system.

Atmosphere↗
PubMed1992

Planetary Protection Policy (U.S.A.).

Through existing treaty obligations of the United States, NASA is committed to exploring space while avoiding biological contamination of the planets, and to the protection of the Earth against harm from materials returned from space. Because of the similarities between Mars and Earth, plans for the exploration of Mars evoke discussions of these Planetary Protection issues. US Planetary Protection Policy will be focused on the preservation of these goals in an arena that will change with the growth of scientific knowledge about the martian environment. Early opportunities to gain the appropriate data will be used to guide later policy implementation. Because human presence on Mars will result in the end of Earth's separation from the martian environment, it is expected that precursor robotic missions will address critical planetary protection concerns before humans arrive.

Containment of Biohazards↗
PubMed1995

Cometary origin of the biosphere: a progress report.

Empirical evidence of the accretion temperature for undifferentiated meteorites coming from the asteroid belt, combined with any reasonable temperature gradient extending from the asteroid belt to the Earth's zone, suggests that the Earth accreted from very hot dust grains that were degassed from all volatile elements and depleted in labile compounds. Isotopic evidence from the atmospheric noble gases also shows that no primary atmosphere has survived on the Earth. The only possible source for the atmosphere and the oceans is therefore the cometary bombardment that is predicted as the inescapable consequence of the formation of the giant planets. This implies that comets are the only source of organic carbon, nitrogen and water, hence of the total biosphere of the Earth.

Atmosphere↗
PubMed1998

A search for extraterrestrial eukaryotes: physical and paleontological aspects.

Physical and biochemical aspects of a proposed search for extraterrestrial eukaryotes (SETE) are considered. Such a program should approach the distinction between a primitive eukaryote and an archaebacteria. The emphasis on gene silencing suggests a possible assay suitable for a robotic investigation of eukaryoticity, so as to be able to decide whether the first steps towards eukaryogenesis have been taken in an extraterrestrial planet, or satellite. The experiment would consist of searching for cellular division and the systematic related delay in replication of heterochromatic chromosome segments. It should be noticed that the direct search for a membrane-bounded set of chromosomes does not necessarily determine eukaryotic identity, as there are prokaryotes that have membrane-bounded nucleoids. A closer look at the protein fraction of chromatin (mainly histones) does not help either, as there are some eukaryotes that may lack histones; there are also some bacteria as well as archaebacteria with histone-like proteins in their nucleoids. Comments on the recent suggestion of possible environments for a SETE program are discussed: the deep crust of Mars, and the Jovian satellite Europa, provided the existence of an ocean under its ice-covered surface is confirmed by the current Galileo mission.

Biological Evolution↗
PubMed1986

Chemical effects of large impacts on the Earth's primitive atmosphere.

Intense bombardment of the moon and terrestrial planets approximately 3.9-4.0 x 10(9) years ago could have caused the chemical reprocessing of the Earth's primitive atmosphere. In particular, the shock heating and rapid quenching caused by the impact of large bodies into the atmosphere could produce molecules such as HCN and H2CO4 which are important precursors for the abiotic synthesis of complex organic molecules. Here we model the production of HCN and H2CO by thermochemical equilibrium and chemical kinetic calculations of the composition of shocked air parcels for a wide range of temperatures, pressures and initial compositions. For atmospheres with C/O > or = 1, our results suggest that bolide impacts cause HCN volume mixing ratios of approximately 10(-3) to 10(-5) in the impact region and global average ratios of 10(-5) to 10(-12). The corresponding H2CO mixing ratios in the impact region are 10(-7) to 10(-9); no-global mixing can occur, however, as H2CO is rapidly destroyed or rained out of the atmosphere within days to hours. Rainout to the oceans of 3-15% of the HCN produced can provide approximately (3-14) x 10(11) mol HCN per year. This is somewhat larger than other predicted sources of HCN and H2CO on the primitive Earth.

Atmosphere↗
PubMed1994

Impact melting of frozen oceans on the early Earth: implications for the origin of life.

Without sufficient greenhouse gases in the atmosphere, the early Earth would have become a permanently frozen planet because the young Sun was less luminous than it is today. Several resolutions to this faint young Sun-frozen Earth paradox have been proposed, with an atmosphere rich in CO2 being the one generally favored. However, these models assume that there were no mechanisms for melting a once frozen ocean. Here we show that bolide impacts between about 3.6 and 4.0 billion years ago could have episodically melted an ice-covered early ocean. Thaw-freeze cycles associated with bolide impacts could have been important for the initiation of abiotic reactions that gave rise to the first living organisms.

Amino Acids↗
PubMed2001

Assessing the plausibility of life on other worlds.

As the field of astrobiology matures and search strategies for life on other worlds are developed, the need to analyze in a systematic way the plausibility for life on other planetary systems becomes increasingly apparent. We propose the adoption of a simple plausibility of life (POL) rating system based on specific criteria. Category I applies to any body shown to have conditions essentially equivalent to those on Earth. Category II applies to bodies for which there is evidence of liquid water and sources of energy and where organic compounds have been detected or can reasonably be inferred (Mars, Europa). Category III applies to worlds where conditions are physically extreme but possibly capable of supporting exotic forms of life unknown on Earth (Titan, Triton). Category IV applies to bodies that could have seen the origin of life prior to the development of conditions so harsh as to make its perseverance at present unlikely but conceivable in isolated habitats (Venus, Io). Category V would be reserved for sites where conditions are so unfavorable for life by any reasonable definition that its origin or persistence there cannot be rated a realistic probability (the Sun, gas giant planets). The proposed system is intended to be generic. It assumes that life is based on polymeric chemistry occurring in a liquid medium with uptake and degradation of energy from the environment. Without any additional specific assumptions about the nature of life, the POL system is universally applicable.

Biological Evolution↗
PubMed2003

Impacts and evolution: future prospects.

The discipline of astrobiology includes the dynamics of biological evolution. One of the major ways that the cosmos influences life is through the catastrophic environmental disruptions caused when comets and asteroids collide with a planet. We now recognize that such impacts have caused mass extinctions and played a major role in determining the evolution of life on Earth. The time-averaged impact flux as a function of projectile energy can be derived from lunar cratering statistics as well as the current population of near Earth asteroids (NEAs). Effects of impacts of various energies can be modeled, using data from historic impacts [such as the Cretaceous-Tertiary (KT) impactor 65 million years ago] and the observed 1994 bombardment of Jupiter by fragments of Comet Shoemaker-Levy 9. It is of particular interest to find from such models that the terrestrial environment is highly vulnerable to perturbation from impacts, so that even such a small event as the KT impact (by a projectile 10-15 km in diameter) can lead to a mass extinction. Similar considerations allow us to model the effects of still smaller (and much more likely) impacts, down to the size of the asteroid that exploded over Tunguska in 1908 (energy approximately 10 megatons). Combining the impact flux with estimates of environmental and ecological effects reveals that the greatest contemporary hazard is associated with impactors near 1 million megatons in energy (approximately 2 km in diameter for an asteroid). The current impact hazard is significant relative to other natural hazards, and arguments can be developed to illuminate a variety of public policy issues. The first priority in any plan for defense against impactors is to survey the population of Earth-crossing NEAs and project their orbits forward in time. This is the purpose of the Spaceguard Survey, which has already found more than half of the NEAs >1 km in diameter. If there is an NEA on a collision course with Earth, it can be discovered and the impact predicted with decades or more of warning. It is then possible to consider how to deflect or disrupt the NEA. Unlike other natural hazards, the impact risk can be largely eliminated, given sufficient advanced knowledge to take action against the threatening projectile.

Directed Molecular Evolution↗
PubMed2003

Synchronized SETI-the case for "opposition".

If the signals being sought in search for extraterrestrial intelligence (SETI) programs exist but are brief (for example, they are produced intermittently to conserve energy), then it is essential to know when these signals will arrive at the Earth. Different types of transmitter/receiver synchronization schemes are possible, which vary in the relative amount of effort required by the transmitter and the receiver. The case is made for a scheme that is extremely simple for the receiver: Make observations of a target when it is at maximum angular distance from the Sun (i.e., "opposition"). This strategy requires that the transmitter has accurate knowledge of the distance and proper motion of the Sun and the orbit of the Earth. It is anticipated that within the next 10-20 years it will be possible to detect directly nearby extrasolar planets of approximately terrestrial mass. Since extraterrestrial transmitters are expected to have significantly more advanced technology, it is not unreasonable to expect that they would be able to detect the presence of the Earth and measure its orbit at even greater distances. This strategy is simple to implement, and opposition is also typically the time when observations are easiest to make. Limited opposition surveys contained in a number of all-sky surveys have already been performed. However, full-sky opposition surveys are best suited to detectors with very large fields of view.

Artificial Intelligence↗