Astronomy 141 - Life in the Universe - Autumn Quarter 2009 episodes:

• October 30, 2009Lecture 26: The Deserts of Mars

  For many, the most likely place in the Solar System to search for life

  beyond the Earth is Mars. This lecture describes the properties of

  Mars, a desert world with a thin, dry, cold carbon dioxide atmosphere.

  I will review evidence that has begun to point unequivocally to the

  conclusion that Mars had flowing and standing liquid water on its

  surface in the past, perhaps during the first billion years or so.

  If Mars had a warm, wet past, did life also get a start there?

  Recorded live on 2009 Oct 30 in Room 1005 Smith Laboratory on the

  Columbus campus of The Ohio State University.

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• October 29, 2009Lecture 25: The Requirements for Life in the Solar System

  Having completed our tour of the Solar System, we now turn to a

  discussion of the requirements for life, and where those requirements

  might be satisfied elsewhere in the Solar System. Some - energy,

  complex chemistry, and liquid water - seem obvious, but they are not the

  only possibilities or considerations. At the end, we will have a short

  list of possible places to look, some expected, others surprising.

  Recorded live on 2009 Oct 29 in Room 1005 Smith Laboratory on the

  Columbus campus of The Ohio State University.

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• October 28, 2009Lecture 24: The Jovian Planets

  We turn our attention to the Giant Planets of the outer Solar System:

  the gas giants Jupiter and Saturn, and the ice giants Uranus and Neptune.

  We will review their structure and properties, and then examine their

  systems of moons, with special attention to the giant moons. While the

  Jovian planets themselves seem unlikely places to hunt for life in our

  Solar System, a few of their largest moons may be more promising than

  appears at first sight. We'll explore this further in subsequent lectures

  in this unit. Recorded live on 2009 Oct 28 in Room 1005 Smith Laboratory

  on the Columbus campus of The Ohio State University.

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• October 27, 2009Lecture 23: Terrestrial Worlds in Comparison

  We follow our tour of our Solar System with an in-depth comparison of

  the Terrestrial Planets. In particular, we want to contrast and compare

  their geological and atmospheric histories. This will inform our

  inquiry into whether or not we expect to find life on these worlds.

  Recorded live on 2009 Oct 27 in Room 1005 Smith Laboratory on the

  Columbus campus of The Ohio State University.

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• October 26, 2009Lecture 22: The Family of the Sun

  This first lecture of Unit 4 - Life in the Solar System - is a quick

  tour of our Solar System reviewing the planets, dwarf planets, moons,

  and small bodies that make up our celestial home. This lecture will

  introduce many of the places we will be considering in detail over the

  next two weeks, and which we'll find around other stars. Recorded live

  on 2009 Oct 26 in Room 1005 Smith Laboratory on the Columbus campus of

  The Ohio State University.

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• October 22, 2009Lecture 21: Impacts and Extinction

  We end our exploration of life on the Earth with a look at death in the

  fossil record. This lecture looks at the role asteroidal impacts have

  played in the history of the Earth, and their possible role in mass

  extinction events in the fossil record. We will discuss near-earth

  asteroids, historical impacts, and the K-T event in which a massive

  asteroid impact caused a mass extinction of species that included all

  non-avian dinosaurs among its victims, opening up the biosphere to the

  dominance of mammals. We'll look at other mass extinctions during the

  past 500Myr, and talk about whether extinction-class impacts are in our

  future. Recorded live on 2009 Oct 22 in Room 1005 Smith Laboratory on

  the Columbus campus of The Ohio State University.

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• October 21, 2009Lecture 20: The History of Life on Earth

  In this lecture we step back and look at the history of life on Earth

  from the first signs of life at start of the Archaean Eon 3.5 billion

  years ago to just up to the present day. We will review the appearance

  of photosynthesis and the rise of oxygen in the atmosphere in the

  Proterozoic, the appearance of the first eukaryotes and sexual

  reproduction, and the Cambrian explosion of plant and animal species at

  the start of the Phanerozoic Eon, and briefly review the changes in life

  to the present day from the Cambrian Explosion to the colonization of

  land by plants and then animals. Most of the lecture will be where most

  of the time was spent, in the early, microbiological Earth. Recorded

  live on 2009 Oct 21 in Room 1005 Smith Laboratory on the Columbus campus

  of The Ohio State University.

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• October 20, 2009Lecture 19: The Origin of Life on Earth

  How did life arise from non-life? Frankly, we don't know, but current

  experimental work is aimed at trying to understand how it might work in

  biochemical terms. This lecture sets out the problem of "abiogenesis",

  and describes our current thinking about the likely origins of life on

  Earth. We will review the classic Miller-Urey experiment, and look at

  its insights and limitations, discuss meteoritic sources of amino acids,

  and the basic requirements needed for protolife. I will then describe

  in outline two scenarios that are active areas of origins research: the

  RNA World model and the Metabolism First model. Finally, I will very

  briefly mention Exogenesis and Panspermia, which don't really address

  the problem of abiogenesis so much as move it elsewhere. Recorded live

  on 2009 Oct 20 in Room 1005 Smith Laboratory on the Columbus campus of

  The Ohio State University.

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• October 19, 2009Lecture 18: The First Living Things on Earth

  What are the first recognizable forms of life that we find in the

  geological record? How far back can we go in geological time and still

  find life? This lecture reviews three lines of evidence that have

  emerged in recent years to suggest that life may have emerged very early

  on the young Earth, perhaps within a few hundred million years of the

  end of the epoch of heavy bombardment. I will describe fossil

  stromatolites, microfossils, and carbon isotope data that are used to

  explore these questions. Recorded live on 2009 Oct 19 in Room 1005

  Smith Laboratory on the Columbus campus of The Ohio State University.

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• October 16, 2009Lecture 17: Life on the Edge

  Extremophiles are organisms that are adapted to survive in extreme

  environments. This lecture describes the challenges that

  extremes of heat, cold, acidity, salinity, and radiation pose to

  organisms, and show examples of how evolution has nonetheless allowed

  some organisms to adapt to not just survive but thrive in such extreme

  conditions. Finally, we will explore the possible limits of life on

  Earth, and find that while you can make things pretty extreme and still

  have organisms adapt, you reach the limit if there is no water. Rather

  than being oddballs, these organisms give us important insights into the

  origins of life on Earth, and widens the possibilities for life on other

  worlds. Recorded live on 2009 Oct 16 in Room 1005 Smith Laboratory on

  the Columbus campus of The Ohio State University.

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