Astrobiology: What areas of scientific research are you currently interested in and involved with?
"The ubiquity and adaptability of the microbial realm is one of the big scientific finds of the latter several decades of the twentieth century."
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Dr. Boston: I work on various aspects of the search for life on other planets. I study extremophile organisms in harsh environments on Earth like caves, deserts, the high alpine, and the poles. I am interested in the global biogeochemical cycles and how a planet and its life coevolve and whether it does or does not behave as a cohesive higher order complex system. I also have a long interest in human life support in space and on other planets, especially Mars. My most far-flung interest is in the feasibility of introducing life onto a lifeless planet and seeing whether that life can persist and become its own biosphere.
Astrobiology: What are you looking for when you explore the underground caves in Mexico?
Dr. Boston: We are investigating the fundamental energy gathering mechanisms of organisms living in a highly acidic, sulfur-dominated environment. We are observing the myriad weird forms that these organisms produce. We are also trying to make connections between microbial activities and the secondary minerals that are produced in the cave and enhanced dissolution and precipitation rates of various minerals because of the presence of these organisms.
We have found amazing microbial forms including "snottites" (rubbery bacterial strings that resemble stalactites in shape), thick microbial mats forming hieroglyphic mud-like patterns on the cave walls, gooey linings of hydrogen sulfide and carbon monoxide gushing springs that we are calling "phlegm ball mats" and many more.
Astrobiology: How does the search for life in extreme environments on Earth relate to the search for extraterrestrial life in our solar system and beyond?
Dr. Boston: We are both extending our fundamental understanding of the limits to life, in the broader context, here on Earth and also practicing to look for it elsewhere.
To practice for this future search, we have continued to extend our search for life on this planet into ever more unlikely places. Seemingly, each time we reach out to another improbable environment for life on Earth, we find it there. The terms “extreme life”, “extremophiles”, and “extreme environments” have been widely adopted to describe this new realization. The ubiquity and adaptability of the microbial realm is one of the big scientific finds of the latter several decades of the twentieth century and is shaping our understanding of life and our search for it elsewhere in the universe for the twenty first century.
However, we are not really searching just for extreme environments on other planets. Actually, what we have defined as "extreme" here on Earth is really a reflection of our personal preference in habitat, i.e. what humans find to be "comfy". Another planet may have typical conditions that we would find extreme, but our range of conditions might be "extreme" for that planet. Really, studying life in extremes on Earth is a "stretching exercise" for imaginations as we apply them to the search for life elsewhere.
Astrobiology: Life on Earth is essentially the only standard by which scientists can measure and compare other life forms. Knowing this, how will it be possible to recognize alien forms of life if this life is drastically different from life on Earth? In other words - what is life and how will we recognize it?
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"One of the biggest problems that we face in looking for extraterrestrial life is actually figuring out what we mean by the word 'life'."
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Dr. Boston: One of the biggest problems that we face in looking for extraterrestrial life is actually figuring out what we mean by the word “life”. We have only tentative operational definitions of life. Processes like reproduction and reducing internal entropy at the expense of the environment are often in voked. But are those sufficient conditions to make something “alive”? How sure are we that reproduction is an essential part of life? It may be an essential part of a biosphere subject to Darwinian evolution as we understand it, but is that a necessary property of life? We can easily imagine (and many science fiction writers have!) alternative modes of life possessing few properties that we recognize as signs of life in the life we know on this planet.
Even on Earth, where we know there are living things everywhere, biologists studying unusual microorganisms in exotic environments often ask the question “Is it REALLY alive?” Geomicrobiologists, mineralogists, and micropaleontologists face an even tougher question…“Was it EVER alive?” We have learned from direct experience in our cave research that even with investigators on site, using sophisticated analyses, and taking samples back to well-equipped laboratories, the status of a natural object as now alive, once alive, or never alive can be equivocal. How much more challenging, then, will it be to conduct such studies in environments like Mars, Europa, or someday to apply these techniques to the data from extrasolar planets?
We believe that there are two important approaches that must be applied in parallel. The first is analysis of features that might be expected in any living system, no matter what its fundamental chemistry may be. These features could be termed “universals”. An example of a possible universal is the presence of compounds that could not exist in the absence of life processes, that is, free oxygen as a highly reactive molecule could not exist in thermodynamic equilibrium without the intervention of something like life to continually recycle it. The second approach is to build a compendium of knowledge and techniques based on our experience in Earth environments. Our work in caves and the work of other researchers in the far fringes of Earth environments are advancing both of these approaches.
Astrobiology: Theories of cosmic ancestry propose that life on Earth originated from bacterial spores carried here on meteorites and asteroids. Is it likely that any life, even hardy bacterial life, could have survived the many hazards (with freezing temperatures, deadly cosmic rays and ultraviolet radiation being a few examples) that would have been encountered on such a journey?
Dr. Boston: This is a very complicated question. The idea you mention, known as "panspermia" historically, was advanced both in the early part of the 20th century and later by Fred Hoyle and colleagues. At the time, there was no evidence to support such ideas, as intriguing as they were. They fell out of favor and were largely pooh-poohed. However, recent evidence that chunks of Mars have found their way to Earth over the course of millions of years has muddied the question of the location of life's origin in our solar system. If stuff can go back and forth, what are the chances that primeval microorganisms were transported from Mars to Earth, thus seeding Earth, or from Earth to Mars (less likely due to orbital dynamics constraints) thus seeding Mars with life? Of course, this has prompted several researchers to seriously study the survivability of microorganisms in small rocky bodies like meteorites when subjected to conditions similar to those they would face on the journey from one planet to another.
Clearly, any organisms on the surface, or near the surface of such bodies would be subjected to the nasty factors you mention in your question. However, microorganisms are very good at inhabiting small fissures and intergrain spaces in rocks here on Earth as we have discovered within the past 20 years. These buried lifeforms may be protected from the challenges of space and subsequent re-entry heating and ablation. Dr. Gerda Horneck of the European Space Agency is currently studying these issues in conjunction with several colleagues at NASA Ames Research Center in California.
"The surface of Mars is pretty unlikely as a habitat for any kind of life that we can understand at present."
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As for the long-term, inter solar-system transport possibilities, it is hard to gauge the chances. We do know that freeze-dried micro-oganisms are pretty resistant to environmental conditions because their metabolism has ceased totally. They are subject to destruction from ionizing radiation, however their radiation cross-section is very small. In addition, sufficient rocky material around them would shield them from this. Th ey could potentially remain revivable for immensely long periods, if these are the only factors to be considered.
The other questions that are unanswerable now are 1) what is the likelihood of lifeforms surviving any processes that would eject them from the parent system (planets exploding? stars going nova? etc.) Secondly, what are the probabilities that such bodies would later find themselves involved in the formation of a later generation of solar system formation? Or, what are the probabilities that such bodies would make their way to an existing solar system? What are the probabilities of capture by the new solar system? What are the probabilities of landing on a planet suitable for their rehydration and growth? What are the probabilities that they would survive re-entry into atmosphere and impact into a new planet? You can see that we have virtually no grasp of any of these variables at present. Nevertheless, in principle, I believe that it is possible, just not very likely in the face of how much "space" is in space and how little plantetary stuff there is.
Astrobiology: Based on the present hostile conditions on Mars (such as frigid temperatures, a barren surface and negligible atmosphere), what form of life would be likely to proliferate or survive there?
Dr. Boston: In my opinion, the surface of Mars is pretty unlikely as a habitat for any kind of life that we can understand at present. This is why we published a paper in 1992 (Boston, McKay and Ivanov, in the journal ICARUS) suggesting that the subsurface of Mars was the place that life would most likely have persisted on a planet that appeared to have been more clement in its early history, but has become ever less so over its history. So, I am predisposed to think that this is the place to look. We know that on Earth there is a huge biodiversity of microorganisms in the rocks, caves, and aquifers to depths at least as great as 7-10km. It has also been suggested relatively recently that the subsurface might even be the location of the origin of life on Earth in the first place. I won't debate the merits of that argument here, but it may be possible that Mars could have given rise to life in the subsurface and had an exclusively subsurface biosphere for all of its history.
We are large multicellular creatures of the surface only becoming aware of microorganisms in the past 120 years, and only becoming aware of the subsurface biota in the past 20 years. No wonder we haven't considered it much yet. Of course, touching on my earlier points about our needing to broaden our understanding of life on Earth as much as possible so that we can even imagine where to look for life on other planets is illustrated by this whole situation. We have been imagining that a planet with life on it must have it everywhere, hanging out on the surface being pretty obvious. We really don't have any reason to assume that Earth's biosphere is representative of all biospheres on planets everywhere.
I rule out consideration of such science fictiony notions as "silicon life", "rock life", and weirder stuff because we currently don't have the slightest idea whether such things are possible and whether we could recognize them if they did exist is debatable. If such things exist, it will be fascinating if we can one day find and recognize them.
Astrobiology: What do you enjoy the most about being a microbiologist? What do you enjoy the least?
Dr. Boston: Read and think about the areas which interest you as much as possible. Ask questions all the time, and don't worry if they seem 'stupid' or unpopular. It is important to do well at school, especially in mathematics and statistics, but the most importants things of all are imagination, enthusiasm, self-motivation, independence and inspiration! Also, make as many contacts with scientists as you can - ask questions, talk to people, think for yourself!
And don't expect to get rich or even to have a smooth career - academic research in particular is an _extremely_ competitive and poorly paid area of work. Perhaps only 10% of people who do science PhDs in the UK will get permanent jobs in their area of specialization.
Astrobiology: How did you become interested in space, science and microbiology?
Dr. Boston: I was a kid in the 1960's and totally enamored of space and other sciences. I knew that I wanted to become some sort of scientist by the time I was 9 or 10 years old although I didn't know what kind of science. I loved astronomy, biology, geology, paleontology, and archaeology. So, I finally decided that I would somehow pursue all of them in some way. I was discouraged by many people from doing this because they thought that it indicated a lack of seriousness or focus. From my point of view, it was necessary because I function as something of a synthesist taking pieces of information from many areas and bringing them to bear upon large issues that require a multi-disciplinary approach. I have managed to carve out a field of study that encompasses almost all of my scientific loves.
Astrobiology: What advice can you offer to students interested in pursuing careers in the biological sciences?
Dr. Boston: This is a tough one. I love what I do, but there is no denying that it can be a difficult row to hoe. I hate it when scientists act as mindless "cheerleaders" for science to young people. Science is wonderful, but it is not always "non-stop fun". There is a lot of work involved, often tedious and uninspiring in itself. There are the difficulties of having to compete with others for jobs, projects, funding, recognition. There are endless deadlines, rejections, and setbacks in the work itself and in the scientific community within which we all work. Nevertheless, if it is what someone loves, then it will be worth it to them.
On the upside, I believe that this century we are just entering will be the era of biology. The past century was the era of the machine, of engineering and chemistry. Now, we are probing the very nature of our genetic code and that of all living things on Earth. This is an immensely powerful wave that will carry us to both new frontiers and also present us with an array of problems only some of which are being seen so far. It will be a very exciting time to be in the biological sciences, but also scary. There will be both ethical, societal, psychological, and political consequences of the explosion of biological knowledge and biological engineering (in the wider sense) that will accompany the science.
I guess all I can really offer for advice is, if you love it, go for it, but do so with your eyes wide open to reality.
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