Louis Irwin

• Doctor of Philosophy
• Professor Emeritus at The University of Texas at El Paso

The recent and still controversial claim of phosphine detection in the venusian atmosphere has reignited consideration of whether microbial life might reside in its cloud layers. If microbial life were to exist within Venus' cloud deck, these microorganisms would have to be multi-extremophiles enclosed within the cloud aerosol particles. The most s...

No magnetotrophic organism on Earth is known to use magnetic fields as an energy source or the storage of information. However, a broad diversity of life forms is sensitive to magnetic fields and employs them for orientation and navigation, among other purposes. If the magnetic field strength were much larger, such as that on planets around neutron...

Most definitions of life assume that, at a minimum, life is a physical form of matter distinct from its environment at a lower state of entropy than its surroundings, using energy from the environment for internal maintenance and activity, and capable of autonomous reproduction. These assumptions cover all of life as we know it, though more exotic...

The vast majority of neurobiologists have long abandoned the Cartesian view of non-human animals as unconscious automatons—acknowledging instead the high likelihood that mammals and birds have mental experiences akin to subjective consciousness. Several lines of evidence are now extending those limits to all vertebrates and even some invertebrates,...

Cognitive science today increasingly is coming under the influence of embodied, embedded, extended, and enactive perspectives, superimposed on the more traditional cybernetic, computational assumptions of classical cognitive research. Neuroscience has contributed to a greatly enhanced understanding of brain function within the constraints of the tr...

There are four principal habitats in which life may exist—the surface of a planetary body, its subsurface, its atmosphere and space. From our own experience we know that life does exist on the surface of a planet, in its subsurface and transiently at least in the atmosphere. Where it is present, it exists in a surprising diversity and in a variety...

The definition of life is a long-standing debate with no broadly accepted scientific consensus (Kolb 2007). The underlying problem in defining life is twofold. The first is that living systems use compounds that are abundant in the surrounding environment, and processes that are not intrinsically different from reactions that occur abiologically. T...

Life is based on complex chemistry yet only a few of all the available elements participate in most life-supporting reactions on Earth: carbon, nitrogen, oxygen, hydrogen, phosphorous, and sulfur. Of these, the most characteristic element of biological systems is carbon. In this chapter we will discuss why carbon is so favored by life on Earth and...

In this chapter we go beyond the search for geoindicators and biosignatures that might point to the presence of life, with the specific aim of detecting and confirming the presence of life. First, we review the results and interpretations of the Viking mission—the only life detection experiment ever conducted on another planetary body to date. We a...

All the known planetary bodies and satellites in our Solar System are within reach of current technology for the detection of a number of the biosignatures and geosignatures that could indicate the possibility of harboring some form of life. In this chapter, we will review the strength of that possibility for each of the planets and the best studie...

The discussion of life on other worlds is inevitably qualified by the phrase, “life as we know it.” This customary and appropriate caution among scientists serves to (1) admit that all our speculations and extrapolations are based on a known sample size of only one, and (2) imply that the one form of life we know may be peculiar to the physical con...

The future of life on Earth and elsewhere in the Universe is the least studied of the three fundamental questions posed by NASA’s Astrobiology Roadmap (Des Marais and Walter 1999; Des Marais et al. 2003, 2008). A lack of focus on this question raises two concerns. First, in a sense, the future of life is the question that has the greatest practical...

In this chapter we will elaborate on how evidence for life on other worlds can be sought, and if present, possibly detected. The best evidence for extraterrestrial life, of course, would be recovery of actual specimens or their fossils. For the next one or two decades, the possibility of obtaining such direct evidence is almost surely restricted to...

Science and speculation have converged at the boundaries of human imagination to conceive of some very exotic states of matter and/or energy that have been claimed by their authors to represent alternative forms of life or to exhibit life-like characteristics. Those ideas have been advanced by serious thinkers and thus deserve to be evaluated in th...

Cite this article: Effect of exercise in combination with dietary nopal and zucchini on chronic and acute glucohomeostasis in genetically obese mice. Inte J Expe Bio. 2018; 1(1): 001-005. ABSTRACT Objective: Type 2 Diabetes Mellitus (DM) is a major health problem for which folk medicinals such as nopal, or cactus stems from various species of Opunt...

This class-tested textbook examines the basic elements of living systems: energy, chemistry, solvents, and habitats in crucial depth. These elements define the opportunities and limitations for life on other worlds. The book argues that life forms we would recognize may be more common in our solar system than many assume. It also considers, however...

Both robotic and human missions into space are necessary for an effective program of space exploration. For the nations that have sent humans into space (Russia, China, and the United States) the competition for limited budgets between human and robotic exploratory strategies is inevitable. Yet, the two strategies are complimentary and mutually sup...

The study of exoplanets has revolutionized the scientific field of planet formation and changed scientific and public views on the possible frequency of life in the Universe. This has been motivated, at least to some extent, by the search for a second Earth. It started slowly with the first unambiguous evidence for an extrasolar planet announced by...

The Search for Extraterrestrial Intelligence, or SETI, has traditionally been conducted and coordinated by the SETI Institute, based in Mountain View, California (USA). The SETI institute is a non-profit organization, which carries out not only research associated with possible extraterrestrial intelligent life, but also research related to planeta...

An external energy source is a necessary condition for life, because living systems require a flow of energy to organize materials and maintain a low state of entropy (Morowitz 1968). Energy is also needed to perform work. Life on Earth can be distinguished by the external energy source that it uses. Photoautotrophic life derives energy from sunlig...

Life as we know it consists of chemical interactions that take place in the liquid state, yet the requirement that life be liquid-based is not normally part of anyone’s definition of a living system. Thus, we cannot state categorically that life in either a solid or gaseous state is impossible. There are, however, compelling theoretical advantages...

The origin of life is a large and active field of research, and one chapter in this book can hardly do it justice. Yet, if we are to make reasonable inferences about the probability of life on other worlds, we must be able to gauge the possibility that living systems could have arisen (or arrived) there in the first place. And that, in turn, depend...

Rational speculation about biological evolution on other worlds is one of the outstanding challenges in astrobiology. With the growing confirmation that multiplanetary systems abound in the universe, the prospect that life occurs redundantly throughout the cosmos is gaining widespread support. Given the enormous number of possible abodes for life l...

Environmental conditions can change drastically and rapidly during the natural history of a planetary body. These changes affect the biosphere and can spur evolution via the mechanism of directional selection leading to the innovation of new processes and forms of life, or alternatively leading to the extinction of certain life forms. Based on the...

Olfaction in rodents provides an excellent modality for the study of cellular mechanisms of information processing and storage, since a single occurrence of precisely timed stimuli has high survival value. We have followed up preliminary evidence of cytokine and proteinase involvement in normal (as opposed to pathologically-induced) brain plasticit...

a b s t r a c t The next step in the exploration of Mars should include a strong and comprehensive life detection component. We propose a mission called BOLD: Biological Oxidant and Life Detection mission. The scientific objectives of the BOLD mission are to characterize habitability of the martian surface and to search for evidence of extinct or e...

The presence of microbialite structures in a freshwater, dimictic mid-latitudelake and their establishment after the last ice age about 10,000 years ago is puzzling.Freshwater calcite microbialites at Pavilion Lake, British Columbia, Canada, consist of acomplex community of microorganisms that collectively form large, ordered structuredaggregates....

In the next few years, the number of catalogued exoplanets will be counted in the thousands. This will vastly expand the number of potentially habitable worlds and lead to a systematic assessment of their astrobiological potential. Here, we suggest a two-tiered classification scheme of exoplanet habitability. The first tier consists of an Earth Sim...

Born from clumps of Stardust spinning around a central sun, the planets of our Solar System, like most planets in the universe, began their voyage through time with a rich mixture of chemistry and energy on board. From such a cauldron, life emerged on our planet Earth early, and diversified into the great variety of living organisms that cover the...

Our survey of the possibilities for life in our Solar System has left us with the strong likelihood that ours is the only world with intelligent species, the only one on which at least one species has acquired technology, and quite possibly the only planet orbiting our Sun that hosts organisms of great size, complexity, and diversity. We will now t...

Now that we’ve talked about the source of solar systems, the nature of life, the relevance of chemistry, and the importance of energy, we need to think about how life can arise in an otherwise non-living world, then give rise to the interdependent web of organisms that constitute ecosystems. And we need to do so in a fairly general way, so our assu...

Saturn was the furthest planet from Earth in the known Solar System in 1655, and the crude telescopes available at the time revealed an enigma. At times, the planet looked like it had "handles" on either side, but at other times the handlelike bulges disappeared. Christiaan Huygens, born into a wealthy Dutch family of high status, was given an allo...

Speculation that alien life might be found on other worlds can be traced to ancient times. Copernicus, Kepler, and Galileo fed those thoughts by showing that the Earth is not the center of the universe. Once it was understood that our planet is just one of several rotating around a solar center, thoughts of other solar systems naturally arose. By 1...

Linda Morabito was four years out of college with a degree in astronomy when she became a navigation engineer for the Voyager mission. On 5 March 1979, Voyager 1 made its closest approach to lo, taking pictures that revealed a world utterly unlike any yet seen in the Solar System (Figure 9.1a).

Gangliosides have long been implicated in multiple pathologies affecting the central nervous system. Empirical studies have suggested the possibility that gangliosides, particularly GD3, work in tandem with pro-inflammatory cytokines, especially tumor necrosis factor alpha (TNFα), to initiate or facilitate cell death in the CNS. As a step toward un...

Every 175 years, the outer gas giants line up in a way that makes the shortest and most energetically efficient pathway from Earth to each of them possible. In the mid 1960s, when it was realized that this infrequent window would open up between 1976 and 1978, a grand tour of the outer planets and their satellites was planned for the robotic explor...

Europa is on everyone’s short list of destinations for finding life in the Solar System beyond Earth. This is because water is found there in abundance, almost surely in liquid form, protected from the harshness of space by a thick layer of ice. But the ice is restless, cracking continually and moving about in rafts and slabs that reflect the push...

On 15 December 1970, the Soviet lander, Venera 7, radioed good news and bad news back to Earth. The good news was that it had landed softly enough on the surface of Venus to still be intact and talking, the first man-made object to do so from the surface of another planet. The bad news was that, at a temperature of 470°C and an atmospheric pressure...

Looks can be deceiving. Every close-up picture of the surface of Mars has revealed what appears to be a barren, stony, still, and totally lifeless landscape (Figure 5.1). We do know the atmosphere is dynamic, since from a distance we can see that winds on Mars can get high enough to kick up global dust storms that last for weeks. For all we can tel...

Suppose there were two intelligent beings - let’s call them scientists - sitting on a planet orbiting Epsilon Eridani, a star just over 10 light years from Earth. They are writing a book about how life could evolve on other worlds. Their technology is a little more advanced than ours, but not by much. For example, they’ve developed powerful remote...

Our material universe, as best we can tell, is around 13.7 billion years old. Our Solar System has existed for about a third of that time. Thus, the possibility that life has had much longer than we have had to evolve in other regions of the cosmos is obvious. But has it, and is it still there?

The skies are cloudy on seven of the eight planets in our Solar System. They are thick and global on Venus, Jupiter, and Saturn. Uranus has hazy clouds, while those on Mars and Neptune are thin and wispy. Partly cloudy would be a more accurate description for the clouds on Earth, which are never global but can be locally thick and extensive. Becaus...

A distinctive assemblage of freshwater calcite microbialites was studied at Pavilion Lake, British Columbia, Canada, using standard microbial methods, morphological observations, PLFA analysis, and biochemical analysis to identify cell-signalling (quorum sensing) compounds.

The authors propose a method for comparing two samples of curves. The notion of similarity between two curves is the basis of three statistics they suggest for testing the null hypothesis of no difference between the two groups. They exploit standard tools from functional data analysis to preprocess the observed curves and use the permutation distr...

Life is based on complex chemistry yet only a few of all the available elements participate in most life-supporting reactions on Earth: carbon, nitrogen, oxygen, hydrogen, phosphorous, and sulfur. Of these, the most characteristic element of biological systems is carbon. In this chapter we will discuss why carbon is so favored by life on Earth and...

To study regulatory mechanisms of ganglioside biosynthesis, genes for sialyltransferase II (ST2) or acetylgalactosaminyltransferase I (GalNAcT) were transfected into different cell lines of a substrain of murine neuroblastoma F-11 cells (F-11A). While complex β-series ganglioside synthesis is negligible in the parental line, cells transfected with...

To investigate the interaction between sex, stressors, and dietary choice in rats, a preferred diet under the influence of chronic mild stressors was empirically determined to consist of soybeans and cookies in addition to lab chow. This preferred mixed diet was then tested for its influence on several behavioral tests at the end of prolonged expos...

Here we review the results and interpretations of the Viking mission - the only life detection experiment ever conducted on another planetary body. We also examine the claim of fossilized life in the Martian meteorite ALH84001, which sparked renewed attention to the analysis of other meteorites from Mars. Finally, we will provide a brief overview o...

The future of life on Earth and elsewhere in the universe is the least studied of the three fundamental questions posed by NASA's Astrobiology Roadmap (Des Marais and Walter 1999; Des Marais et al. 2003). A lack of focus on this question raises two concerns. First, in a sense, the future of life is the question that has the greatest practical signi...

In this chapter we will elaborate on how evidence for life on other worlds can be sought, and if present, possibly detected. The best evidence for extraterrestrial life, of course, would be recovery of actual specimens or their fossils. For the next one or two decades, the possibility of obtaining such direct evidence is almost surely restricted to...

The discussion of life on other worlds is inevitably qualified by the phrase, "life as we know it." This customary and appropriate caution among scientists serves to (1) admit that all our speculations and extrapolations are based on a known sample size of only one, and (2) imply that the one form of life we know may be peculiar to the physical con...

Robotic and human exploration should proceed together to meet the challenges of discovery on other worlds. The history and characteristics of Mars make it the most suitable target for human exploration. With orbiters and rovers already there, the next goal should be to assemble a permanent robotic station, which would aid in the systematic explorat...

The origin of life is a large and active field of research, and one chapter in this book can hardly do it justice. Yet, if we are to make reasonable inferences about the probability of life on other worlds, we must be able to gauge the possibility that living systems could have arisen (or arrived) there in the first place. And that, in turn, depend...

The Viking mission was the only mission to date that conducted life detection experiments. It revealed ambiguous and still controversial results. New findings and hypotheses urge a re-evaluation of the Viking results and a re-evaluation of the evidence for the possible presence of life on Mars in general. Recent findings of abundant water ice on Ma...

The Viking mission was the only mission to date that conducted life detection experiments. It revealed ambiguous and still controversial results. New findings and hypotheses urge a re-evaluation of the Viking results and a re-evaluation of the evidence for the possible presence of life on Mars in general. Recent findings of abundant water ice on Ma...

While depression is reportedly more prevalent in women than men, a neurobiological basis for this difference has not been documented. Chronic mild stress (CMS) is a widely recognized animal model, which uses mild and unpredictable environmental stressors to induce depression. Studies of chronic stress, mainly in males, have reported an increase in...

The nature of life on Earth provides a singular example of carbon-based, water-borne, photosynthesis-driven biology. Within our understanding of chemistry and the physical laws governing the universe, however, lies the possibility that alien life could be based on different chemistries, solvents, and energy sources from the one example provided by...

1] As the environmental histories of Earth and Mars have diverged drastically after the first few hundred million years, so would the history of any life on them. While Earth has had liquid water on its surface for billions of years, Mars most likely had long dry and cold environments interspersed with warmer and wetter periods. Life thrived on Ear...

The distinctive assemblage of freshwater calcite microbialites discovered at Pavilion Lake, BC, has been associated with organisms such as Epiphyton and Girvanella, fossils from just before the Cambrian explosion about 550 million years ago (Laval et al., 2000). The presence of the microbialite structures in a dimictic mid-latitude lake and their e...

Methanesulfonyl fluoride (MSF) is a CNS-selective acetylcholinesterase (AChE) inhibitor, currently being developed and tested for the treatment of symptoms of Alzheimer's disease. We have previously confirmed that a single in utero exposure to MSF at clinically appropriate doses inhibits AChE activity in fetal rat brain by 20%, and when administere...

Life is based on complex chemistry yet only afew of all the available elements participate in most life-supporting reactions on Earth: carbon, nitrogen, oxygen, hydrogen, phosphorous, and sulfur. Of these, the most characteristic element of biological systems is carbon. In this chapter we will discuss why carbon is so favored by life on Earth and w...

Science and speculation have converged at the boundaries of human imagination to conceive of some very exotic states of matter and/or energy that have been claimed by their authors to represent alternative forms of life or to exhibit life-like characteristics. Those ideas have been advanced by serious thinkers and thus deserve to be evaluated in th...

There are four principal habitats in which life may exist – the surface of aplanetary body, its subsurface, its atmosphere and space. From our own experience we know that life does exist on the surface of aplanet, in its subsurface, and transiently at least in the atmosphere. Where it is present, it exists in asurprising diversity and in avariety o...

The discussion of life on other worlds is inevitably qualified by the phrase, “life as we know it.” This customary and appropriate caution among scientists serves to (1)admit that all our speculations and extrapolations are based on aknown sample size of only one, and (2)imply that the one form of life we know may be peculiar to the physical condit...

Because of their limited lipid synthesis ability it has been postulated that Giardia lamblia trophozoites depend on lipid remodeling reactions, to generate parasite-specific phospho and glycolipids. We have shown earlier that exogenous bile acids and lipid molecules are taken up by Giardia through active transport and by other mechanisms. Another r...

Global changes in gene expression were analyzed in pericontusional tissue taken during surgery from 4 patients with traumatic brain injury (TBI), in cerebral infarction tissue from a patient with vasculitis and in normal brain tissue resected during craniotomy for meningioma. Of approximately 1,200 genes showing some level of expression by cDNA mic...

The neurochemical control of learning depends on several neurotransmitters, hormones, and neuropeptides. Cortistatin is a neuropeptide with sleep-modulating properties that regulates memory consolidation and evocation. Several reports have suggested that learning processes are expressed under diurnal variations; therefore, it seems that the efficie...

We simulated the major environmental stresses on and near the Martian surface and recorded their effects on microbial populations of E. coli and D. radiodurans. Viability rates were determined for the populations under the single and combined stresses of sub-zero temperature, low-pressure, and UV radiation in salt-water soil and fresh-water soil at...

Although a melatonin/dopamine relationship has been well established in nonmotor systems wherein dopamine and melatonin share an antagonist relationship, less clear is the role melatonin may play in extrapyramidal dopaminergic function. Therefore, the purpose of the present experiments was to examine the relationship between melatonin and the dopam...

Several observations indicate that the cloud deck of the venusian atmosphere may provide a plausible refuge for microbial life. Having originated in a hot proto-ocean or been brought in by meteorites from Earth (or Mars), early life on Venus could have adapted to a dry, acidic atmospheric niche as the warming planet lost its oceans. The greatest ob...

Energy, chemistry, solvents, and habitats -- the basic elements of living systems - define the opportunities and limitations for life on other worlds. This study examines each of these parameters in crucial depth and makes the argument that life forms we would recognize may be more common in our solar system than many assume. It also considers, how...

Life as we know it consists of chemical interactions that take place in the liquid state, yet the requirement that life be liquid-based is not normally part of anyone's definition of a living system. Thus, we cannot state categorically that life in either a solid or gaseous state is impossible. There are, however, compelling theoretical advantages...