Astrobiology seeks to understand the origin of the building blocks of life, how these biogenic compounds combine to create life, how life affects - and is affected by the environment from which it arose, and finally, whether and how life expands beyond its planet of origin.
None of these questions is by any means new - but for the first time since they were posed, these questions may now be answerable. Astrobiology seeks to provide a philosophical and programmatic underpinning whereby life's place in the universe can be explored - at levels of inter-related complexity ranging from molecular to galactic.
At first, one might not think that their field of expertise might be relevant to Astrobiology. Indeed, with Astrobiology's cosmic perspective, they could well see their interests as being somewhat distant from such an expansive endeavor. Dive into even the most superficial description of Astrobiology and you'll soon see that not only are a vast array of scientific and engineering disciplines involved, but that the intersection points between these disciplines are often novel.
At some point everyone has a stake in Astrobiology. The challenge which lies ahead is not so much the framing of questions as it is of how to channel all relevant expertise to the right task so as to answer these questions. It also requires the willingness of all participants to challenge old assumptions and conceive of novel ways to do things.
As Albert Einstein once said, "the universe is stranger than we can imagine". None the less, armed with this caveat, Astrobiologists should never stop trying to imagine how the universe works - nor shy away from attempting to understand their personal place amidst its splendor and mystery.
You can be an astrobiologist simply by deciding that you are one.
How do life and the world upon which it resides affect each other over time?
Oceanographers and climatologists will be called upon to help understand how life and the planet upon which it arose affect the composition of that planet's atmosphere. At issue is understanding how oceans and atmospheres form, how they interact to perpetuate the conditions necessary for life, how changes in atmosphere and ocean can change the course of evolution, and how the activity of lifeforms can in turn, alter the character of a planet's atmosphere and its oceans.
But Earth is just one planet - and hardly representative of all of the worlds in this solar system. What happens to life on a planet (Mars) when its oceans dry up (or sink into the ground) and most its atmosphere escapes into space with the remainder freezing out at its poles? Can the same life-inducing steps which occurred on Earth be initiated on a world (Europa) where a thick ice crust has a high radiation vacuum environment on one side and a liquid ocean on the other - one where the main energy source is not from a star but from the tidal interactions with a giant gas planet?
On the immediate front: how do all of these interactions between air, water, and life on Earth bode for the way we are transforming our planet? Can we control the process in time to prevent serious consequences? Have we initiated a process that would otherwise occur naturally? That is, is the inevitable consequence of a planet's fostering of intelligent life the modification of its biosphere? If we have managed to alter Earth's biosphere in a haphazard, unplanned fashion, could lessons be derived from this uncontrolled experiment such that we could deliberately transform an inhospitable world (terraform it) into one capable of supporting life?
How do you assess a planet's life history?
Paleontologists, evolutionary biologists and perhaps even archaeologists will be called upon to help understand the record of previous life on Earth in a planetary context - that is, what lessons can we learn from unraveling our own past to guide us as we figure out what happened on other planets? It is in this context that the planetary geologists and astronomers join in. What are the implications that can be drawn from Earth's fossil record regarding the time and rate at which life forms in a planet's history? Does complexity arise at a constant rate or does it happen in spurts? Do changes in planetary environments lead or follow periods of change? Do events of external origin such as large impacts, a nearby supernova, or stellar variations affect the pace and character of life's evolution? Does life arise as soon as conditions permit? Does life arise only to be extinguished by cataclysmic events only to arise again? Is it possible to truly extinguish life once it has spread across (and within) a planet?
Can we expect to find fossils on other worlds? If so, where do we look? Was Mars' early history similar enough to Earth's that evidence of life can be found as easily as it is on Earth? Can planets swap material containing fossils? If so, what are the implications for the exchange of living material between planets? If material is exchanged, is this a rare or common phenomenon? Can fossil records on several planets be used to calibrate if/when such exchanges occurred and whether foreign life forms managed to thrive?
How do you get from simple chemistry to self-replicating life forms?
Organic and inorganic chemists, information theorists, geneticists and molecular biologists will be called upon to understand how self-replicating systems arose and how they evolved to include information coding and metabolic control. Of interest to Astrobiology is what non-living materials and environments participated in the origin of self-replicating chemical systems. What materials were required? Can we replicate these conditions today? Are there alternate systems, which could arise from different starting materials? Were there competing primordial life systems - and if so did one win out over the other or did they merge into a single biology?
Also of interest is understanding what the earliest genetic systems looked like, whether analogs exist on Earth today, and whether current organisms contain molecular fossils (i.e. ancient components retained throughout evolution) which can provide insights into early genetic systems.
Life in extreme environments - is this how life started on Earth - and is this what we can expect to find on other worlds?
Microbiologists, ecologists, oceanographers, organic and inorganic chemists, and geologists will be called upon to understand the environmental extremes within which life can exist on Earth. Life has been found miles beneath Earth's crust, in the deepest portions of the sea, in caustic and boiling water, within nuclear reactors, inside of Antarctic rocks, and amid toxic waste sites. Life is now thought to have arisen on Earth in hot, hostile conditions.
As such, are the extremes within which terrestrial life thrives indicative of the environments within life can arise elsewhere? Do these environments suggest the range of environments on other worlds wherein life can survive? Do they indicate the places where we might find remnants of ecosystems on worlds such as Mars that have undergone extreme climatic change? Industrial microbiologists and pharmaceutical researchers may also be enlisted inasmuch as a number of enzymes isolated form extremophiles have already been put to significant scientific and commercial use.
Large scale planetary impacts: Ecosystem devastation and recovery.
Astronomers, planetary geologists, and paleontologists will be called upon to assess the effect that large impacts have upon life on Earth. A clear record of bombardment in the early history of the solar system has been found strewn across many planets and moons. Several years ago we watched a comet hit Jupiter with many times the force of our planet's collective nuclear arsenal. On Earth it is clear that large ecosystem-busting impacts have occurred with some regularity. Do these impacts explain any of the paths taken during the evolution of life on Earth? Are planetary impacts a "natural" component of life's evolution on a planet? If so, does the rate of impacts accelerate or retard the evolution of new life forms? Indeed, do frequent impacts during a planet's youth erase life one or more times before it finally takes hold?
A steady, daily influx of meteoritic material, putative extraterrestrial fossils found within the Martian meteorite ALH84001, recent analyses of cometary composition, serve to heighten interest in the role that extraterrestrial materials had in the origin of life on Earth. Did oceans on Earth and Mars result from cometary impacts? What role does this constant influx of materials play in a planet's ecosystem? Can viable organisms be transferred between planets - i.e. do we need to consider an ecology where more than one planet's biota are involved? Can small collections of biogenic materials be concentrated on otherwise abiotic worlds - such as the poles of Earth's moon? If the materials striking Earth contain biogenic compounds, what does this say about the ability for life to originate within comets and other small bodies?
Planetary protection: preventing an undesirable interplanetary mix of life forms
Epidemiologists, microbiologists, ethicists, spacecraft engineers, and environmental health professionals will be called upon to assess how we protect ourselves and our planet's biosphere from harmful extraterrestrial life forms - as well as what steps we take to be certain that we do not contaminate other worlds. How do we sterilize spacecraft so as to prevent the contamination of other worlds with terrestrial life forms? How do we return samples from other worlds in a manner that adequately reduces the risk of accident while maintaining the integrity of the sample? If life forms from two different planets come into direct contact will this encounter be benign or detrimental? Can microbes from one planet cause disease in an organism from another planet?
Is it possible to send humans to other worlds (such as Mars) without contaminating those worlds? Can spacesuits be designed so as to not contaminate a planet's surface? Is planetary contamination the inevitable consequence of human exploration? If we find a world that is devoid of life - at what point are we certain enough that we do not worry about contaminating this world? - After all, life has been found miles below Earth's surface and similar habitats could elude detection on other worlds? If life is found on another world, does it have a "right" to exist free of terrestrial contamination? How do we decide whether or not it is safe an ethically acceptable to terraform a planet?
Extrasolar planets: finding them and evaluating their biological potential
Astronomers, climatologists, and ecologists will be called upon to devise a strategy whereby extrasolar planets capable of fostering the development of life can be located. Recent discoveries seem to show that planet formation is a common phenomenon in the universe. While only large Jupiter-class planets have been detected thus far, it is only a matter of time before smaller, Earth-class planets are expected to be found.
Can these planets be directly imaged? What do we look for when we try to ascertain where a planet supports life? Can planetary phenomena indicative of life be detected across interstellar distances? Are there aspects of a planet's atmospheric composition that are indicative of the disequilibria we expect life to maintain? Are there aspects of ice-covered ocean world such as Europa which can be detected from a distance? Are we going to look for evidence chemistries that are different than those than Earth-based life uses? Can we determine what the habitable zone is for a star? Can planets - and the conditions for life arise in multiple star systems?
Are there features a technological race leaves that can be detected across interstellar distances? Do these features outlive their creators? Are we going to be looking for Dyson spheres or other means whereby a star's output is harnessed or modified? Will we be looking for star systems with more than one habitable world, perhaps terraformed planets? Does the act of traversing interstellar space leave detectable traces? (are some gamma ray bursts actually from starships?)
Is life a natural consequence of planetary formation?
Geologists, astronomers, chemists, and climatologists will be called upon to understand how planets accrete, how they differentiate, how they recycle materials, and how these factors combine to create and sustain an environment conducive to life's origin and perpetuation.
Are stellar birth processes and protoplanetary disk formation common (and inherently similar) phenomena? That is, do similar materials go into the formation of planets across the universe - and is our solar system similar to these other solar systems? If life is found on worlds other than Earth, how common is it throughout our solar system? Throughout the universe? If life is common in our solar system can this be extrapolated to other solar systems - indeed, the entire universe?
Searching for - and communicating with - extraterrestrial intelligence
Radio and optical astronomers, telecommunication providers, cryptographers, linguists, psychologists, ethicists, and journalists will be called upon to devise and operate the search for extraterrestrial intelligence (SETI). Although a shortsighted American Congress terminated government support for this effort, it continues none the less. The technological ability to search for and identify candidate signals experiences a doubling effect in less than a year.
Can we devise strategies, which provide an adequate survey of the sky? Will we know an artificial signal when we find one? If we recognize the signal - can we decode it - and will we understand it? Is there anything to be learned for communicating with non-human species such as apes and whales? Can we continue to conduct this search on Earth as sources of radio interference are on the rise? Will we need to move SETI into space or perhaps to the far side of the Earth's Moon to escape interference? Are we looking at all of the possible ways that communication can occur across interstellar distances? If we receive a message, should we reply? If so, who composes the message and how do we send it?
Nervous systems: how did Earth affect their development - and how will they respond to the space environment?
Neuroscientists and behaviorists will be called upon to understand how life evolves the ability to exchange information within and between organisms - and how these organisms obtain information from and feed it back into their external environment.
What environmental stimuli led to the evolution of nervous systems? What role does a gravitational field play in the development and organization of an organism's nervous system? Can this nervous system develop normally in altered gravity environments? Can the nervous system of a individual raised in microgravity fully adapt to life in a 1G environment? How does an organism reared in microgravity sense position and direction? Can nervous systems evolve with the ability to intercept - and create types of energy not currently seen in terrestrial life forms - e.g. radio, microwave, magnetic, and x-ray?
Muscle and Bone: what happens when weight-bearing structures no longer have weight to bear?
Bone, muscle, and exercise physiologists, developmental biologists, comparative anatomists, neurophysiologists, kinesiologists, and rehabilitation therapists will be called upon to understand how life develops internal architectural support systems, how these systems are articulated for movement, and what role gravity plays in the evolution, development, operation, and maintenance of these systems. Musculoskeletal systems serve to support organisms against the pull of gravity as well as to allow movement within a gravitational field. Skeletal systems utilize common minerals to form architectures which constantly adapt and readapt to usage patterns and forces. Muscle control can involve complex neural mechanisms that are honed by experience as an organism reacts to its environment. Yet these supportive architectures and modes of movement are the result of billions of years of development within the forces imposed by a gravitational field. Removal from gravity imposes operational challenges these systems have never been called upon to react to.
Did skeletal systems evolve to utilize the materials at hand or is their a evolutionary preference for one material vs another? Do musculoskeletal systems develop normally in the absence of a gravitational field? Do these systems develop sufficiently to allow an organism to live out its life in microgravity? Can the musculoskeletal systems of organisms raised in microgravity function normally when exposed to normal gravity? How do these systems respond to gravitational fields greater than that on Earth? Do life forms on other planets evolve structures and modes of movement similar to terrestrial organisms or are there other possible solutions? Is flight more prevalent on worlds with gravity less than Earth's and less common on worlds where gravity is greater than Earth's?
How are the raw ingredients of life formed, distributed, and recycled in the universe?
Astronomers and astrophysicists will be called upon to understand how stars produce the elements required for life, how these materials are organized into planetary systems, how these materials are processed during planetary system evolution, and how they are recycled when the host star goes supernova or lost when the host star fades and dies.
Is there a galactic ecology wherein biogenic materials are produced and recycled though stars? How prevalent are so called "organic compounds" across the universe? Are there other compounds that might be indicative of life? How are these materials organized and concentrated such that life can form? Are some regions of our galaxy that are more (or less) likely to contain biogenic precursors? Are planets and moons the only places wherein life or its immediate precursors can form?
What is the smallest, most fundamental level at which life perceives and responds to gravity?
Cell physiologists and physicists will be called upon to ascertain the smallest level of biological organization at which gravity (or lack thereof) can be perceived, transduced, and responded to. Gravity is the only environmental factor whose presence and strength has remained constant throughout life's tenure on Earth. Gravity is also the only environmental factor who's presence cannot be removed (for more than a few seconds) on or near Earth' surface. As such, life has never been placed in a situation where gravity wasn't present.
Have biological processes evolved which depend upon the presence of gravity? Are there biological processes that are insensitive to gravity's presence or absence? Is there a threshold level of gravity at which sensory mechanisms respond to gravity? At which level(s) of organization can life forms detect the presence and direction of gravity? Do gravity dependent biological phenomena respond to other forces in the environment? Do gravity-sensing mechanisms develop in organisms, which are raised in the absence of gravity? Do the sensory capabilities of microgravity-raised organisms function normally when exposed to gravity? What is the maximum gravitational field within which life can evolve?
What will it take for terrestrial life to survive and adapt to environments in space and on other planets?
Spacecraft engineers, life support engineers, human factors scientists, evolutionary biologists, ecologists, physicians, environmental toxicologists, and psychologists will be called upon to understand what is required to support humans and other Terran life forms in extraterrestrial environments - in space and upon planetary surfaces.
What sort of countermeasures will we need to develop to deal with the debilitating effects of microgravity and space radiation? Can humans and other life forms readapt to life on Earth after adapting to live in microgravity or in the lower gravitational fields on the Moon and Mars? Can life forms be modified to better function in extraterrestrial environments? Should they be modified? Should we modify only adults or pre-adapt children? ? Can children born in extraterrestrial colonies adapt to life on Earth? Can humans even reproduce in space? If we decide to terraform other worlds, what forms of life will we seed these worlds with? Can we modify exiting terrestrial life forms? Do we need to create new ones?
How will human culture adapt and evolve in extraterrestrial environments?
Everyone mentioned above, plus people with no particular expertise, will be called upon to understand what it will take for humans and other terrestrial life forms to survive, thrive, and evolve within new environments in space and upon other worlds.
Aside from the biomedical issues, will humans bring existing social and cultural values with them as they spread out across the universe? What sort of new cultural adaptations will be made? At what point will humans living off-Earth identify more with their current home and less with Earth? Should plans be made before settling other worlds as to how these worlds will be self-governing or should we just let human nature take its course? Will microgravity environments alter the way humans interact with one another? What might happen on a world with low gravity where humans could conceivably strap on wings and fly? How will humans adapt to long periods of space travel - possibly taking more than one human lifetime to complete? How might hibernation make long space flights more tolerable and what happens when people wake up in the future? If humans spread out across the stars will they stay in touch with other worlds or sever all ties?
What happens if we meet another sentient species?
Why are we so interested in leaving Earth to explore the universe?
People with no scientific or technical training will be called upon to validate that such research is of real benefit. Perhaps the benefit is not immediate - but it should, none the less, be relevant.
What is it that propels us to expand and explore beyond the horizon? Is this an innate human characteristic or one passed on from generation to generation though cultural means?
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