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7 - The principles of life (selections)
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- By Tibor Gánti
- Mark A. Bedau, Reed College, Oregon, Carol E. Cleland, University of Colorado, Boulder
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- Book:
- The Nature of Life
- Published online:
- 10 November 2010
- Print publication:
- 30 September 2010, pp 102-112
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- Chapter
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Summary
THE CRITERIA OF LIFE
Living and non-living systems are qualitatively different, i.e., living systems have qualitative properties or groups of qualitative properties which occur exclusively in the living world and cannot be found in the non-living world. In what follows, these common characteristics found in living organisms will be called life criteria, the laws uniting these characteristics will be considered the principle of life, and life itself as a common general abstraction of every kind of living being will be accepted as a philosophical and not a biological category. Life criteria will be dealt with in the present chapter, and the principle of life will be discussed in connection with the organization of the chemoton. Life as a philosophical category will not be dealt with in the present book.
The selection and axiomatically exact formulation of life criteria is of fundamental importance in theoretical biology. As we have seen, classical biology has not been able to solve this problem during its long history of 2000 years. We shall present here a quite new system of life criteria, which entirely differ from the classical “life phenomena.” This new system of life criteria was first proposed in the original edition of this book in 1971.* However, in the diverse world of biology it is not easy to select fundamentally common characteristics, since it is impossible to find a research worker who could claim to know every part of the living world with the required precision.
13 - Life in the dark dune spots of Mars: a testable hypothesis
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- By Eörs Szathmáry, Collegium Budapest, Tibor Gánti, Collegium Budapest, Tamás Pócs, Eszterházy Károly College, András Horváth, Konkoly Observatory, Ákos Kereszturi, Eötvös University, Szaniszló Bérczi, Eötvös University, András Sik, Eötvös University
- Edited by Ralph Pudritz, McMaster University, Ontario, Paul Higgs, McMaster University, Ontario, Jonathon Stone, McMaster University, Ontario
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- Book:
- Planetary Systems and the Origins of Life
- Published online:
- 13 August 2009
- Print publication:
- 06 December 2007, pp 241-262
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Summary
Introduction
This chapter presents one of the very rare exobiological hypotheses. The main thesis is that there could be life in the dark dune spots (DDSs) of the southern polar region of Mars, at latitudes between –60° and –80°. The spots have a characteristic annual morphological cycle and it is suspected that liquid water forms in them every year. We propose that a consortium of simple organisms (similar to bacteria) comes to life each year, driven by sunlight absorbed by the photosynthetic members of the consortium. A crucial feature of the proposed habitat is that life processes take place only under the cover of water ice/frost/snow. By the time this frost disappears from the dunes, the putative microbes, named Mars surface organisms (MSOs) must revert to a dormant state. The hypothesis has been worked out in considerable detail, it has not been convincingly refuted so far, and it is certainly testable by available scientific methods. We survey some of the history of, the logic behind, the testable predictions of, and the main challenges to the DDS-MSO hypothesis.
History
The spots in question were observed on images made by the Mars orbiter camera (MOC) on board the Mars Global Surveyor (MGS) spacecraft between 1998 and 1999 (images are credited to NASA/JPL/Malin Space Science Systems). These features appear in the southern and northern polar regions of the planet in the spring, and range in diameter from a few dozen to a few hundred metres.