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← Origins of Life: Astrobiology and General Theories for Life - Origins of Life and Astrobiology

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Showing Revision 6 created 03/02/2020 by yadavaryal.

  1. Hi I'm Sarah Walker and I'm professor at
  2. Arizona State University and I am an
  3. astrobiologist. That studies the origin
  4. of life. And so one of the questions you
  5. might have as an astrobiologist is
  6. why is origin of life so critical to the
  7. study of astrobiology.
  8. Well, astrobiologists are really interested
  9. in whether or not we can identify a
  10. living world so if we can identify
  11. life on another planet.
  12. We wanna discover aliens and
  13. ultimately, the question is whether we'll
  14. be able to distinguish planets that have
  15. life from plants that don't have life. So
  16. in our own solar system, we can actually
  17. send robotic missions to other planets
  18. to look for life on the surface of those
  19. worlds but we're thinking about
  20. exoplanets and planets and distant solar
  21. systems all that we're gonna get is a
  22. little bit of data about the entire planet.
  23. And so, as astrobiologists we are
  24. interested in thinking about life not
  25. only at the scale of individual
  26. organisms, but also at the scale of
  27. entire planets.
  28. And so just to talk about the
  29. magnitude of the problem a lot of people
  30. want to talk about looking at life in
  31. kind of new ways and maybe trying to use
  32. insights from different aspects of known
  33. fields of science to try to understand
  34. how we identify life. And so, on this
  35. slide I'm showing two worlds that are
  36. probably familiar to everyone. Jupiter
  37. and Earth and we know one of these
  38. planets is inhabited and the other isn't.
  39. The inhabited world is obviously our
  40. very own earth, and we can see living
  41. structures on its surface what we see
  42. here is cities at night. When we're
  43. thinking about how to think about the
  44. problem of distinguishing the living
  45. process on Earth from the nonliving
  46. process on Jupiter, it's clear that both
  47. have non-equilibrium structures on
  48. their surfaces. So Jupiter for example
  49. has this great red spot and as I
  50. mentioned, earth has cities. So when we
  51. want to talk about defining the
  52. properties of those planets that are
  53. associated with life, it's not just about
  54. this disequilibra. Clearly cities are
  55. fundamentally different than the great
  56. red spot of Jupiter even though they're
  57. both non-equilibrium structures. So we
  58. have to move a little bit further and
  59. understand the origins of the processes
  60. that led to structure
  61. on the surface of our planet that are
  62. associated with life, and the root of
  63. that question is really to understand
  64. what's the probability of life emerging
  65. on a planet and how can we actually
  66. understand that as a planetary scale
  67. process. And there's really two ways of
  68. constraining the likelihood of life
  69. emerging on a planet. We don't
  70. think that Jupiter is a living planet. Obviously
  71. based on our observations of Jupiter, it
  72. could be that it might satisfy some
  73. definition of life down the road if we
  74. actually come up with a theory for life
  75. and Jupiter satisfies that theory but
  76. right now we don't think Jupiter's alive.
  77. And so we need some observations of
  78. other living world to constrain the
  79. probability of life right now earth is
  80. the only example we know and so to do
  81. that we actually have to detect alien
  82. life and determine its abundance. And so
  83. this is the way you usually people think
  84. about astrobiology is actually looking
  85. at other worlds trying to identify if
  86. there's aliens on those worlds and then
  87. maybe we would actually be able to
  88. constrain the probability that a planet
  89. like Earth is going to emerge life on
  90. its surface and a planet like Jupiter is
  91. not. But we can also think about theory
  92. and experiment to constrain the
  93. probability for life. And from this view
  94. the idea is really to try to uncover
  95. what are the universal principles of
  96. life that might actually allow us to
  97. build predictive models for the
  98. circumstances under which life should
  99. emerge. So, we would have some a priori
  100. theory that would enable us to predict P(life)?
  101. the probability of life emerging.
  102. And so with the Jupiter and Earth
  103. example I gave that theory should be
  104. able to account for the differences that
  105. it's not just a non-equilibrium process
  106. on the surface of a planet but in the
  107. case of formation of cities or forests
  108. or any of the kind of rich structure
  109. that we see on earth that's a product of
  110. biology that the theory would be able to
  111. explain what those things are and be
  112. able to predict what kinds of other
  113. examples of life we might be able to see
  114. on other planets and their likelihood.
  115. But really what we're talking about in
  116. order to constrain the probability of
  117. life is not just to think about the
  118. probability of forests or cities on the
  119. surface of planets as opposed to the
  120. probability of great red spots or other
  121. kinds of dissipative structures that
  122. aren't alive. What we really want is to
  123. understand what's the likelihood of life
  124. even emerging on that planet.
  125. So we really need to be able to solve
  126. the origin of life problem in order to do
  127. astrobiology effectively and constrain
  128. the likelihood of life in the universe.
  129. And so in order to do that, we have to
  130. come up with better theories for origins
  131. of life and be able to understand how
  132. life emerges. And so one of the ways I
  133. like to think about it is really that
  134. we're looking for new principles that
  135. would explain life not just on earth but
  136. life on other planets and I really love
  137. this quote from David Deutsch which I
  138. think articulates very nicely the kind
  139. of processes that are happening on
  140. planets that we really need to be able
  141. to understand in order to understand
  142. life. And he says, base metals can be
  143. transmuted into gold by stars and by
  144. intelligent beings who understand the
  145. processes that power stars and by
  146. nothing else in the universe. So we have
  147. a physics that explains things like
  148. stars or the physics of Jupiter and why
  149. Jupiter has a great storm
  150. on the surface of the planet at the
  151. great red spot. But we don't have a
  152. physics that explains the evolution of a
  153. planet like our own. How life emerges on
  154. that planet, or how it evolves over time
  155. to lead to the kind of diversity of
  156. structures that we have on the surface
  157. of our planet today, like cities and
  158. thinking human beings. Origin
  159. 'life problem is really a problem of how
  160. that entire process of life gets started
  161. in the first place and it's ultimately
  162. critically important to the field of
  163. astrobiology that we understand that
  164. process because we want to know on how
  165. many worlds that occurs.