7 episodes

Life in the Universe UA Science Lecture Series 2015 University of Arizona

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    What is Life?

    What is Life?

    Throughout history, our definition of 'life' reflects our assumptions about how the Universe works – and why we ask the question. The ways different human cultures, ancient and current, have talked about life provide some sense of how we have defined life, and illustrate the aspects of life that fascinate us. Many cultures used life as an analog to explain the movement of winds and currents, or the motions of the planets. Today we use those mechanical systems as analogs for life. Ultimately, we may not really know what life is until we have discovered more than one independent example of it on places other than Earth – we need many diverse examples before we can generalize. But without a definition of what we're looking for, and why we're looking, we may have a hard time recognizing life when we find it.

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    Planet Formation and the Origin of Life

    Planet Formation and the Origin of Life

    It is generally accepted that planets or their satellites are required for life to originate and evolve. Thus, in order to understand the possible distribution of life in the Universe it is important to study planet formation and evolution. These processes are recorded in the chemistry and mineralogy of asteroids and comets, and the geology of ancient planetary surfaces in our Solar System. Evidence can also be seen in the many examples of ongoing planet formation in nearby regions of our galaxy. Finally, the variety of observable extra-solar planetary systems also provides insight into their origins and potential for life. These records will be discussed and compared to summarize our current understanding of planet formation and the accompanying processes that may lead to the origin of life throughout the Universe.

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    Life on Earth: By Chance or By Law?

    Life on Earth: By Chance or By Law?

    Life on Earth is amazing and multifaceted. Ultimately all of life has descended from one common ancestor and has been guided by evolution by natural selection. On the one hand, the evolution of modern-day diversity and ecosystems may have been contingent on the initial chemical building blocks of life and the historical events that have characterized our planet over geologic time. On the other hand, there are numerous aspects of life pointing to regular and deterministic processes that shape the complexity and diversity of life. This talk will touch on those examples where the laws of chemistry and physics, in addition to evolutionary rules, have resulted in general properties of life. These properties ultimately determine how long we live, the diversity of life, the function and regulation of ecosystems and the biosphere, and how life will respond to climate change.

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    Complexity and Evolvability: What Makes Life So Interesting?

    Complexity and Evolvability: What Makes Life So Interesting?

    Life is particularly fascinating in its ability to create complex and ever-changing forms out of simple building blocks. How does such complexity arise, and what are the conditions that allow never-ending evolution of new and more intricate forms of life? We now know that one of the main processes that allows this is that life consists of modules that interact with and feed back on one another. In the history of life on Earth, new levels of complexity have often arisen out of new types of such interactions, and continued evolution has been driven by life interacting with other life. We even find that man-made systems can develop a 'life' of their own when such feedback interactions among many modules occur. Life, it seems, is more about rules of interaction than special materials. We have only begun to understand the power of this algorithmic nature of life.

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    Searching for Life in the Solar System

    Searching for Life in the Solar System

    When Renaissance scholars figured out that the planets are, like Earth, orbiting the Sun, an immediate assumption was that they are inhabited worlds. In the last 50 years, spacecraft have determined that life on the surfaces of planets and moons in the Solar System is rare – if it exists at all. However, there are places where a search for life in the Solar System may still be fruitful. Although the current surface of Mars is a hostile environment, early Mars may have been much more clement to life. Jupiter's moon Europa is almost certainly barren on the surface, but has an 'ocean' of liquid water underneath a crust of ice, where some terrestrial organisms might be able to thrive. Finally, Saturn's moon Titan would not be suitable for life from Earth, but has rain and seas of liquid hydrocarbons, raising questions about whether life needs liquid water, or just needs some abundant liquid.

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    Amazing Discoveries: A Billion Earth-like Worlds

    Amazing Discoveries: A Billion Earth-like Worlds

    One of the most fascinating developments in the last two decades is humankind's discovery of alien worlds orbiting stars near our Sun. Since the first such discovery in 1995 there has been a truly exponential growth in the detection of these new planets. Scientists have been puzzled and surprised by the diversity and extravagance of these new extra-solar systems. For example, we now know the most common type of planet is actually missing from our own Solar System. Recently, the space-based NASA Kepler Mission has discovered thousands of new worlds and suggests that one in five Sun-like stars may harbor an Earth-like planet. We will take a grand tour of some of these amazing new worlds, specifically noting where life might already exist, beyond our Solar System. The latest developments and difficulties of direct imaging for life on an exoplanet will be discussed.

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