Sara Imari Walker

Last updated
Sara Walker
NationalityAmerican
Alma mater Dartmouth College
Florida Institute of Technology
Cape Cod Community College
Scientific career
FieldsPhysics of life, astrobiology, abiogenesis
Institutions Georgia Institute of Technology
NASA Astrobiology Institute
Santa Fe Institute
Arizona State University
Thesis Theoretical Models for the Emergence of Biomolecular Homochirality
Doctoral advisor Marcelo Gleiser
Other academic advisors Paul Davies
Website http://emergence.asu.edu/

Sara Imari Walker is an American theoretical physicist and astrobiologist with research interests in the origins of life, astrobiology, physics of life, emergence, complex and dynamical systems, and artificial life. [1] [2] Walker is deputy director of the Beyond Center for Fundamental Concepts in Science at Arizona State University (ASU), associate director of the ASU-SFI Center for Biosocial Complex Systems and an associate professor at ASU. [3] [4] She is a co-founder of the astrobiology social network SAGANet, and on the board of directors for Blue Marble Space, a nonprofit education and science organization. [1] As a science communicator, she is a frequent guest on podcasts and series, such as Through the Wormhole with Morgan Freeman. [5]

Contents

Education and background

Walker was born and raised in Connecticut. She attended Cape Cod Community College and studied at the Florida Institute of Technology, where she graduated cum laude earning a B.S. in physics in 2005. She earned her Ph.D. in physics and astronomy in 2010 from Dartmouth College. [4] Her thesis was Theoretical Models for the Emergence of Biomolecular Homochirality and her doctoral advisor was Marcelo Gleiser. [6]

Career

After graduating from Dartmouth, Walker began a postdoctoral fellowship at the Georgia Institute of Technology working at the NSF/NASA Center for Chemical Evolution. [4] In 2011 she accepted a NASA Postdoctoral Program Fellowship with the NASA Astrobiology Institute and began working at Arizona State University (ASU). In 2013, Walker became an assistant professor at the School of Earth and Space Exploration as well as the Beyond Center for Fundamental Concepts in Science at ASU. [1] [7] She became a faculty member for the Center for Social Dynamics and Complexity, as well as a graduate faculty member for the Department of Physics and Complex Systems Initiative at ASU in 2014. [3] In 2015, Walker began a fellowship at the ASU-SFI Center for Biosocial Complex Systems as part of a joint educational and research program between Santa Fe Institute and Arizona State University.

Research

Walker is a theoretical physicist and astrobiologist with research interests in the origin of life. [1] [2] She seeks to develop new theories of physics to explain what life is, how it emerged, and what signs of life might look like on other planets. She uses mathematical models to investigate chemical evolution and the development of networks on Prebiotic Earth. [8] She looks at information flow in biotic and abiotic systems to further define life and its emergence. [9] Some of the highlights of her work in this field so far are:

The origin of homochirality

Walker has studied the possible mechanisms of the origin of homochirality, which is a key problem in the origin of life. [10] [11] [12] In her research she has used several models such as the Sandars polymerization model, the Langevin equation, and the activation-polymerization-epimerization-depolymerization (APED) model to imitate potential prebiotic conditions for autocatalytic polymerization networks. Walker et al. discovered that only networks with long polymers show potential to produce significant spontaneous asymmetrical chirality in speculative early Earth conditions. [12] Walker and her colleagues, have also shown that the violent environment of prebiotic Earth would have continuously changed the chirality of reaction networks by a mechanism they termed punctuated chirality. [11] This suggests that the origin of homochirality was not a singular event, and that chiral selection occurred at the same time as the origin of life. Walker and Gleiser also revealed that homochiral proto-domains can form in the middle of racemic networks, and that the slowdown of these networks through processes such as tidal motion or evaporating pools could have led to the stabilization of these structures on early Earth. [10] The results of these simulations have helped to reveal what possibly occurred during the origin of homochiralty, and its effect on the origin of life.

Information flow in biological systems

One of the major challenges in studying the origin of life has been the inability to clearly define what life is. [9] In her investigations, Walker has used the flow of information in systems as a means to distinguish life from non-life. She used the Boolean network model, information theory, and other models to discern feasible universal traits for life. [9] [13] [14] It was shown that in biological systems the components are subordinate to the whole, in what is called top-down causation. [9] Furthermore, a logistical model of Walker et al. suggested that major evolutionary transitions, such as the origin of life, could be characterized by a reverse of information flow in a system from bottom-up to top-down. [15] They also determined that living systems have a separation of data from machinery, and non-trivial replication. Walker has shown theoretically how the occurrence of these biotic traits in an abiotic system present a possible framework for the origin of life. [9]

Public engagement

Walker is an advocate for the communication of science to the public, and has participated in many interviews, panels, and lectures to discuss her research and topics related to her fields of study. [1] She has had press coverage in dozens of news sources, and been active on multiple media platforms. [5] She appeared on the Discover Channel's Through the Wormhole with Morgan Freeman in the episode "Are We Here for a Reason?". She has made two appearances on National Public Radio's Science Friday . [16] She is a co-founder of the astrobiology social network SAGANet, and was a guest scientist on the educational website I'm a Scientist: Get Me Out of Here!. [1] [17]

Her book Life as No One Knows It: The Physics of Life's Emergence comes out in 2024.

Organizations

Walker is a member of multiple scientific organizations, including the Blue Marble Space Institute of Science, the NASA Astrobiology Institute, the Foundational Questions Institute (FQXI), and the International Society for Artificial Life, serving on its board of directors. [18] She is also a member of the Complex Systems Society and is on the board of directors for Blue Marble Space. [1] She is a member of the LifeBoat Foundation and serves on its Astrobiology/SETI Advisory Board. [4]

Selected publications

Awards and honors

Walker has won multiple awards for her teaching, writing, lectures, and contributions to her community. She had been awarded several fellowships:

Related Research Articles

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Astrobiology is a scientific field within the life and environmental sciences that studies the origins, early evolution, distribution, and future of life in the universe by investigating its deterministic conditions and contingent events. As a discipline, astrobiology is founded on the premise that life may exist beyond Earth.

<span class="mw-page-title-main">Hypothetical types of biochemistry</span> Possible alternative biochemicals used by life forms

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<span class="mw-page-title-main">Miller–Urey experiment</span> Experiment testing the origin of life

The Miller–Urey experiment (or Miller experiment) was an experiment in chemical synthesis carried out in 1952 that simulated the conditions thought at the time to be present in the atmosphere of the early, prebiotic Earth. It is seen as one of the first successful experiments demonstrating the synthesis of organic compounds from inorganic constituents in an origin of life scenario. The experiment used methane (CH4), ammonia (NH3), hydrogen (H2), in ratio 2:2:1, and water (H2O). Applying an electric arc (simulating lightning) resulted in the production of amino acids.

<span class="mw-page-title-main">Stanley Miller</span> American scientist (1930–2007)

Stanley Lloyd Miller was an American chemist who made important experiments concerning the origin of life by demonstrating that a wide range of vital organic compounds can be synthesized by fairly simple chemical processes from inorganic substances. In 1952 he performed the Miller–Urey experiment, which showed that complex organic molecules could be synthesised from inorganic precursors. The experiment was widely reported, and provided evidence for the idea that the chemical evolution of the early Earth had caused the natural synthesis of organic compounds from inanimate inorganic molecules.

Homochirality is a uniformity of chirality, or handedness. Objects are chiral when they cannot be superposed on their mirror images. For example, the left and right hands of a human are approximately mirror images of each other but are not their own mirror images, so they are chiral. In biology, 19 of the 20 natural amino acids are homochiral, being L-chiral (left-handed), while sugars are D-chiral (right-handed). Homochirality can also refer to enantiopure substances in which all the constituents are the same enantiomer, but some sources discourage this use of the term.

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Ronald Charles David Breslow was an American chemist from Rahway, New Jersey. He was University Professor at Columbia University, where he was based in the Department of Chemistry and affiliated with the Departments of Biological Sciences and Pharmacology; he had also been on the faculty of its Department of Chemical Engineering. He had taught at Columbia since 1956 and was a former chair of the university's chemistry department.

Thermosynthesis is a theoretical mechanism proposed by Anthonie Muller for biological use of the free energy in a temperature gradient to drive energetically uphill anabolic reactions. It makes use of this thermal gradient, or the dissipative structure of convection in this gradient, to drive a microscopic heat engine that performs condensation reactions. Thus negative entropy is generated. The components of the biological thermosynthesis machinery concern progenitors of today's ATP synthase, which functions according to the binding change mechanism, driven by chemiosmosis. Resembling primitive free energy generating physico-chemical processes based on temperature-dependent adsorption to inorganic materials such as clay, this simple type of energy conversion is proposed to have sustained the origin of life, including the emergence of the RNA World. For this RNA World it gives a model that describes the stepwise acquisition of the set of transfer RNAs that sustains the Genetic code. The phylogenetic tree of extant transfer RNAs is consistent with the idea.

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References

  1. 1 2 3 4 5 6 7 "saraimariwalker". Sara Imari Walker [website appears hacked on 2023-05-03]. Retrieved 2016-11-06.
  2. 1 2 "Emergence@ASU". Emergence@ASU. Retrieved 2016-11-06.
  3. 1 2 "Sara Walker | iSearch". isearch.asu.edu. Retrieved 2016-11-15.
  4. 1 2 3 4 "Lifeboat Foundation Bios: Dr. Sara Imari Walker". lifeboat.com. Retrieved 2016-11-15.
  5. 1 2 "Media". Emergence@ASU. Retrieved 2016-11-15.
  6. ↑ "Recent PhD Graduates | Department of Physics and Astronomy". physics.dartmouth.edu. 18 June 2014. Retrieved 2016-11-15.
  7. ↑ "Sara Walker". Emergence@ASU. Retrieved 2016-11-15.
  8. ↑ Cronin, Leroy; Walker, Sara Imari (2016-06-03). "Beyond prebiotic chemistry" (PDF). Science . 352 (6290): 1174–1175. Bibcode:2016Sci...352.1174C. doi:10.1126/science.aaf6310. PMID   27257242. S2CID   206649123.
  9. 1 2 3 4 5 Walker, Sara Imari; Davies, Paul C. W. (2013-02-06). "The algorithmic origins of life". Journal of the Royal Society Interface . 10 (79): 20120869. arXiv: 1207.4803 . doi:10.1098/rsif.2012.0869. PMC   3565706 . PMID   23235265.
  10. 1 2 Gleiser, Marcelo; Walker, Sara Imari (2009-04-16). "Toward Homochiral Protocells in Noncatalytic Peptide Systems". Origins of Life and Evolution of Biospheres . 39 (5): 479–493. arXiv: 0810.5398 . Bibcode:2009OLEB...39..479G. doi:10.1007/s11084-009-9166-5. PMID   19370399. S2CID   14040409.
  11. 1 2 Gleiser, Marcelo; Thorarinson, Joel; Walker, Sara Imari (2008-10-08). "Punctuated Chirality". Origins of Life and Evolution of Biospheres. 38 (6): 499–508. arXiv: 0802.1446 . Bibcode:2008OLEB...38..499G. doi:10.1007/s11084-008-9147-0. PMID   18841492. S2CID   7005075.
  12. 1 2 Gleiser, Marcelo; Walker, Sara Imari (2008-05-09). "An Extended Model for the Evolution of Prebiotic Homochirality: A Bottom-Up Approach to the Origin of Life". Origins of Life and Evolution of Biospheres. 38 (4): 293–315. arXiv: 0802.2884 . Bibcode:2008OLEB...38..293G. doi:10.1007/s11084-008-9134-5. PMID   18465201. S2CID   18929297.
  13. ↑ Walker, Sara Imari; Kim, Hyunju; Davies, Paul C. W. (2016-03-13). "The informational architecture of the cell". Philosophical Transactions of the Royal Society A . 374 (2063): 20150057. arXiv: 1507.03877 . Bibcode:2016RSPTA.37450057W. doi:10.1098/rsta.2015.0057. PMID   26857675. S2CID   683771.
  14. ↑ Davies, Paul C. W.; Walker, Sara Imari (2016-01-01). "The hidden simplicity of biology". Reports on Progress in Physics . 79 (10): 102601. Bibcode:2016RPPh...79j2601D. doi:10.1088/0034-4885/79/10/102601. PMID   27608530. S2CID   4374728.
  15. ↑ Walker, Sara Imari; Cisneros, Luis; Davies, Paul C. W. (2012-07-19). "Evolutionary Transitions and Top-Down Causation". Proceedings of Artificial Life XIII () P. 2012: 283–290. arXiv: 1207.4808 . Bibcode:2012arXiv1207.4808I. doi:10.7551/978-0-262-31050-5-ch038. ISBN   9780262310505. S2CID   11189805.
  16. ↑ Minoff, Annie (August 5, 2014). "Meet the 'Dune' Readers: Kim Stanley Robinson and Sara Imari Walker". Science Friday.
  17. ↑ "Profile – Calcium Zone". calciumj11.imascientist.org.uk. Retrieved 2016-11-15.
  18. ↑ "List of International Society for Artificial Life Board Members". International Society for Artificial Life. Retrieved 22 May 2021.
  19. ↑ "FQXi Essay Contest 2015". FQXi Community. Retrieved 10 July 2021.
  20. ↑ "FQXi Essay Contest 2012". FQXi Community. Retrieved 10 July 2021.
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