1. Natural Processes that Spread Life Beyond the Planet of Origin:

Transfer of viable microbes between Mars and Earth could have occurred via natural processes. Almost all large comet or meteorite impacts create spallation zones where chunks of surface material near the impact site are only lightly shocked but are accelerated upwards at hypervelocity speeds -- some even at escape velocities. In this way, some of Earth’s material could have been deposited into interplanetary space -- including into a Mars crossing orbit. Within months to years, Mars could have intersected this region of space, attracted the terrestrial debris as small meteorites and deposited the terrestrial surface materials, including the organisms it may have contained, on the Martian surface. Earth meteorites in a Mars crossing orbit have the added advantage of entering the Martian atmosphere slowly enough to arrive at the surface with any microbial passengers still viable.

Mars material could also have arrived on Earth in the same manner. We know in fact of 12 meteorites on Earth that came from Mars. These were only lightly shocked and fell to Earth slowly enough (10-15 km/sec) that their interiors were relatively undamaged at impact. Models show that about a dozen meteorites arrive from Mars to Earth each year in this manner. Most of these meteorites have not been found, but a concerted search could produce more samples.

There are a number of terrestrial microorganisms, including soil bacteria such as Bacillus subtilis, that could survive such interplanetary traverses.

http://www1.tpgi.com.au/users/tps-seti/swaprock.html

Directed panspermia is possible within our solar system and perhaps beyond it. Common soil bacteria -- Bacillus subtilis -- survived unprotected in space aboard the Long Duration Exposure Facility (LDEF) for 6 years. Bacillus spores have been revived from 25-40 million year old Dominican amber (http://pubs.acs.org/hotartcl/ac/96/oct/oct.html ). The ubiquitous bacteria Deinococcus radiodurans has been shown to survive as much as 5 megarads of gamma radiation. In addition, D. radiodurans is extremely resistant to prolonged periods of dehydration (http://jwbrown.mbio.ncsu.edu/micro/MB409/organisms/Deinococcus_radiodurans.html). Survival of microbes in space, especially those protected in some way from UV (such as in soils, clay, or resins) would allow transfer of viable organisms between worlds. It was speculated that such terrestrial organisms could even survive transits between star systems or be used to "seed" distant star forming regions.

The "habitable zone" for terrestrial life is much broader than previously thought. http://www.reston.com/astro/extreme.html#hot

Evolution beyond the planet of origin can involve both directed as well as undirected panspermia. No natural biological barrier to directed or undirected panspermia has been identified to date. However, no organisms more advanced than microbes or plants have spent an entire life cycle beyond Earth and no organisms more advanced than microbes have experienced multiple generations beyond Earth. The value of scientific experiments in biology and medicine carried out on human space missions is extremely high and unique.

The critical near term questions to be answered are whether (and what kinds of) organisms live reproductively successful lives over multiple generations beyond Earth, and what genotypic changes (changes in the genes or DNA sequence) and phenotypic changes (changes an organism's appearance or physiology with or without genetic change) result.

It may be postulated that humanity is entering a new evolutionary territory -- space -- in a manner analogous to the first sea creature crawling out onto the land. This time, however, we will be able to document this evolutionary trajectory with modern scientific instruments, thereby creating a genetic history of extraterrestrial expansion. We have the technological capability to engineer extraterrestrial environments -- and perhaps some of the organisms -- for evolutionary success. With experience, participants were confident that engineering and biotechnology solutions can be found for most, if not all, of life's negative physiological responses to extraterrestrial habitation. Technologically, directed panspermia -- including terraforming -- seems possible.

The pacing element for directed evolution beyond Earth is more cultural than biological or technological. http://www.hq.nasa.gov/osf/heds/hedsplan.html and http://science.nas.nasa.gov/Services/Education/SpaceSettlement/

Gravity shaped life on Earth and will be a primary factor influencing the evolution of terrestrial life beyond Earth. Gravity has always been present on Earth and all organisms have evolved under its influence. A fundamental understanding of its role in living systems is required to understand the basic physiological mechanisms that underlie the evolution, development, and function of microbes, plants, animals and humans on Earth and beyond it.

We know that some biomedical problems can occur with extended stays in space; i.e., bones and muscles lose mass and become weaker; the immune system is altered; the amount of red blood cells decreases; the heart muscle becomes weaker; and there are potential psychological problems associated with long-term confinement. http://www.esb.utexas.edu/roux/set1/sld003.

Solutions to some biomedical problems may be achieved by a better understanding of the fundamental effects of gravity, and its absence, on other living systems. For example. . . Despite expectations to the contrary, frog eggs fertilized in space grew successfully to the tadpole stage, although some anomalies were detected. In 1991, over 2400 tiny jellyfish sent into space on the Space Shuttle showed that detectable behavior changes begin to occur when gravity levels are equal to 24 to 38% of the Earth's gravity -- similar to the gravitational environment of Mars. Rats and other animals have provided many important clues to the causes of some of the most significant biomedical problems seen as a result of living in space. http://www.esb.utexas.edu/roux/set2/sld026.htm

If humans are to spend extended periods of time in space free from the normal pull of Earth's gravity or travel to other bodies in the solar system with gravitational forces different from that of Earth, the most basic questions--how gravity influences living organisms, how they sense their position in relationship to gravity, how they adapt to gravity, to partial gravity, and to no gravity at all--must be answered. Even if the body adapts to life in reduced gravity, there may be serious physiological problems with the readaptation to gravity upon return to Earth. http://www.esb.utexas.edu/roux/set1/sld031.htm

For some organisms, perhaps including humans, embryonic development and birth in low gravity environments may preclude returning to Earth -- unless the right countermeasures are engineered into the artificial ecosystem that sustains them. Fortunately, the International Space Station, which will begin limited but valuable research opportunities in 1999, provides a superb platform for answering these and other questions necessary for engineering an evolutionary future beyond Earth. Its use to address these key Astrobiology investigations is strongly endorsed.

Radiation. Sufficient radiation to almost any portion of the body increases the incidence of cancer, particularly certain types of leukemia. Energetic heavy ions are very effective at causing biological damage, such as cell killing, mutation, neoplastic transformation and cancer. Galactic cosmic rays (GCR) are modified in a very complex way as they pass throughout the spacecraft materials and body tissue. The modified radiation field has a significantly different effect on tissue than the primary radiation.

Space radiation can be a major health risk to crews of long-term missions, like those planned for both the International Space Station and Mission to Mars. The measurement of the radiation dose received during a mission, as well as the energies and charges of particles, is important for assessing health risk. It is also important to obtain quantitative information regarding the effectiveness of space radiation in causing damage to critical biological targets like chromosomes. At present, the estimated uncertainty of biological effects of space radiation is more than a factor of two. Such large uncertainty makes accurate health risk assessment very difficult, if not impossible. Again, the Space Station provides the opportunity to conduct definitive radiation biology experiments in space to better quantitate this risk.

Artificial Ecosystems. http://augusta.msfc.nasa.gov/ed61/papers/rp1324/contents.html

Life exists in ecologies. Engineering an artificial ecosystem that supports successful biological evolution beyond Earth requires, among other things, understanding the co-evolution of life and the environment under different gravity regimes. For example, gases, fluids, and solids behave differently in the microgravity of near Earth orbit or the true free fall environment of interplanetary space than they do on Earth. The habitat environment presents itself differently to the organism in space than one composed of the same constituents does on Earth.

Experience on Spacelab, Mir and Biosphere II shows that there are significant challenges to be met in creating stable artificial ecosystems that have to support people and other plant, animal, and microbial life for very long periods of time in substantially closed environments. When hypogravity and other unusual environmental drivers are introduced, the challenges increase. http://augusta.msfc.nasa.gov/ed61/papers/rp1324/quote.html

It would be prohibitively expensive to carry all the food, air, water, and waste management systems a space crew would need for a three year journey to Mars without recycling these materials. http://augusta.msfc.nasa.gov/ed61/papers/rp1324/chap2.html

Artificial ecosystems for space habitats ( http://library.advanced.org/12145/lss.htm ) will embody regenerative life support ( http://www.bio.purdue.edu/nscort/GIFs/schematic.gif )which recycles a substantial fraction of the materials needed to sustain life through physical-chemical and biological systems http://www.bio.purdue.edu/nscort/homepage.html.

In addition, in situ resources, such as oxygen, carbon dioxide, and water, will be mined from the planetary environment to augment stockpiles for propellants, emergencies and habitability enhancements. http://cass.jsc.nasa.gov/meetings/isru97/isru97.intro.html

A source of liquid water on Mars would greatly enhance our ability to build permanent settlements on Mars. http://www.ees4.lanl.gov/mars/marsworkshop.html

In addition to the challenges of designing Hitchhiker organisms, like those that have been found unplanned and unwanted on all piloted spacecraft, can provide significant challenges for ecosystem stability. These organisms grow in nooks and crannies, clog filters, form biofilms, and may present health hazards. http://shuttle-mir.nasa.gov/science/shuttmir/shutmir/exphis/micph1.html

Once again, the Space Station provides a place to test all of these parameters and to examine issues related to the co-evolution of life and the environment by conducting longitudinal investigations to characterize the buildup and evolution of microbial hitchhikers and other challenges to the stability of artificial ecosystems.

3. Ecology and Evolution

Comparison of various impact events shows that deep in polar ice or deep beneath the ocean (not at hydrothermal vents) are best for surviving the impact of very large comet or asteroids. Organisms on the early Earth -- as well as other worlds -- had to survive a number of planet sterilizing or near sterilizing events during the planet's first billion years because of heavy comet and meteorite bombardment. Episodic large impact events occurred afterwards. Given this, our universal ancestors on Earth were likely to be the thermophilic survivors (who prefer hot temperatures, especially those in the deep in oceans or deep below the ground). After the polar ice caps formed, organisms frozen deep within them would probably also survive a major planetary impact event. Given this, subsurface life on Mars and Europa remains plausible. Determining the genotype, phenotype, and age of organisms in these terrestrial analog environments and comparing them to each other is strongly recommended.

Without biological nitrogen cycling, models indicate there would only be 1/46th of the biota of Earth. All life that we know requires nitrogen to live (it is the "amino" in "amino acids", a major component in DNA, RNA, and proteins). However few organisms can make direct use of atmospheric nitrogen, which is 78% of our atmosphere because the two nitrogen atoms that make up a nitrogen molecule are held together by a triple bond which is exceedingly difficult to break. Because of the relative scarcity of biologically useful nitrogen in the environment, biologically based nitrogen cycling is a critical determinant for the abundance of life on Earth. Life concentrates nitrogen in higher proportions than the environment provides. Thus nitrogen may be one of the better signs of life than carbon for preliminary life detection. Acquisition, utilization, and cycling of nitrogen was one of the early problems that needed to be solved for life to persist on Earth. http://www.cals.ncsu.edu/course/bo360/nutrient/sld005.htm; http://www.copernicus-ny.com/titles/0-387-98270-1.html

4. The Case for Mars

Mars looks good for origin of life. At 4.5 billion years old, the Mars meteorite ALH84001 is the oldest rock on Earth. While speculations on the evidence of fossil life within it remain controversial, there is general agreement that ALH84001 preserves strong evidence of a much warmer, wetter Mars about 3-4 billion years ago -- during the early days of life on Earth. http://www-sn.jsc.nasa.gov/planetscience/marsmet/text.htm

Search for subsurface life on Mars. It is likely that some of the same processes that created caves on Earth also created caves on Mars. By caves, we mean something that a microorganism can inhabit, not necessarily a human -- although human sized caves may also be present on Mars and will almost certainly be more accessible. The Clifford ground water model describing the possibility of a subsurface aquifer on Mars also allows for the possibility of this ground water seeping into Martian caves as terrestrial ground water feeds caves on Earth ( http://www.ees4.lanl.gov/mars/drillingworkshop.html ). Many caves are fed solely by groundwater from below rather than water from above (although both are possible). It is estimated that over 70% of Earth's caves do not have exterior entrances. These caves have been sealed for millions of years, preserving and protecting their remarkable and unique nonphotosynthetic based biota. The Martian subsurface is a potential life site on Mars. Large Martian caves may allow easier access to ground water because deep penetration of the regolith would already have been achieved. Studies of the biology, ecology, and geology of subsurface life and terrestrial caves as analogs to understanding Martian life are strongly recommended.

The decision to expand humanity's biosphere is a statement of its culture, more than a showcase for its technology. Society may emerge through several "types". A Type I society masters the resources of its planet. Humanity is almost at the end of its Type I phase. A Type II society masters the resources of its solar system. This phase has already begun. A Type III society masters the resources of its galaxy. These are different but complement Alvin and Heidi Toffler's waves of civilization. The First Wave was the agricultural wave, where civilization mastered agriculture. This wave dominated civilization for 50,000 years until the beginning of the middle of the 20th century. The Second Wave is the industrialization wave, which began in the 19th century and has almost played itself out in the 20th century. The Third Wave is the information wave, which began in the early 1960’s and is beginning to crest today. The Fourth wave is the fusion of biology, information technology, and space travel where humanity extends beyond Earth. This one is just beginning.

Missions and Technologies:

Space Station has emerged as an important research platform for Astrobiology. The Space Station enables a very wide range of high priority astrobiology studies. Longitudinal studies of the evolution of this artificial extraterrestrial ecosystem could provide practical design information enabling the expansion of terrestrial life beyond Earth while also testing our understanding of ecosystem dynamics. Characterizing the genotype and phenotype changes of the simplest to the most complex terrestrial life aboard Space Station provides critical information about the potential for evolution beyond the planet of origin and establishes the outer boundary of adaptation to hypogravity environments. Exposure experiments described below provide a statistical basis for understanding panspermia. Gas/grain studies reveal the primary mechanisms of planetary accretion, chemistry within the solar nebula, and comet chemistry leading to origin of life. Radiation biology studies provide critical information about radiation/hypogravity limits for evolution beyond the planet of origin as well as providing important practical information for designing radiation protection systems for human exploration of extraterrestrial environments. Space Station also provides the testbed for solving human physiology and life support problems and for creating the artificial environments that can support humanity and other terrestrial life in evolving beyond Earth.

Search for water and life on Mars. Models indicate that an extensive subsurface aquifer may exist in Mars. The most accessible areas are probably at northern plains regions, particularly in low places such as meteor craters, caves, natural depressions, etc. Terrestrial organisms would be able to survive in this type of underground ocean if chemical energy sources were available. For example, hydrogen released from basalt weathering by water and atmospheric carbon dioxide is the energy source for terrestrial methanogenic bacteria (Columbia River Basin basalt subsurface ecosystem, http://www.sciam.com/1096issue/1096onstott.html#3 ). The process of drilling for water on Mars would also provide a core sample that would reveal Mars' climate history. Understanding this history is crucial to understanding issues related to rapid change and ecosystem evolution on early Mars. Reconstructing the Mars history from the Mars meteorite record on Earth reveals a warm, wet Mars as late as 3.6 billion years ago (ALH84001) and a dry cold Mars at 1.3 billion years ago. Discovering what happened to so radically change the Mars environment and determining what happened to the life there (if any) is a central question in Astrobiology. Finding subsurface water is also relevant to future habitation of mars, in the near term for life support and in the long term for ecosynthesis (terraforming -- http://spot.colorado.edu/~marscase/cfm/articles/biorev3.html ).

US/ESA collaborations on Space Station for "beyond planet of origin" exposure/radiation experiments strongly recommended. The Space Station provides an outstanding platform for understanding the probabilities and limitations of life among the planetary bodies of our solar system (and perhaps beyond). Longitudinal studies conducted over the decadal life of the Space Station should focus on survivability of a wide range of terrestrial organisms to the space environment (vacuum, solar radiation, cosmic radiation, microgravity, extreme temperatures). ESA may be willing to supply their Space Exposure Biology Assembly (SEBA) system, which provides an excellent environment for these studies, to U.S. investigators at no cost in exchange for exterior platform allocations on the Space Station.

Explore caves on Earth to understand the possible ecology of extraterrestrial caves. There may be caves on Mars (and Europa? Comets? and Asteroids?). Caves on Earth have yielded some dramatic clues about evolutionary strategies of terrestrial life. In addition to those mentioned above, organisms have been detected in caves that are genetically related to those found in deep hydrothermal vents. Some cave organisms growing on gypsum live at pH 0.0. The ecologies of caves are not only unique from one to another, frequently the ecologies are unique from one "room" in a cave to another. This is a protected and nonphotosynthetic environment that may provide important analogs to subsurface life on other worlds. http://www.i-pi.com/~diana/villaluz

Issues:

Developing an ethical framework for directed evolution within and beyond the planet of origin is recommended. As humanity's technological prowess increases, as fusion occurs among biology, information technologies, and space, evolution will increasingly become a matter of choice as of chance. Developing an ethical framework for this evolution is needs to be a process that occurs beyond NASA. However, because the role of cultural evolution is so intimately connected with directed evolution on this world and others, Astrobiology may be able to provide a forum whereby such discussions can be initiated and supported.