Planet Formation and Panspermia E-Book
198,99 €
Mehr erfahren.
- Herausgeber: John Wiley & Sons
- Kategorie: Lebensstil
- Serie: Astrobiology Perspectives on Life in the Univers
- Sprache: Englisch
An in-depth view of the panspermia hypothesis examined against the latest knowledge of planetary formation and related processes. Panspermia is the concept that life can be passively transported through space on various bodies and seed, habitable planets and moons, which we are beginning to learn may exist in large numbers. It is an old idea, but not popular with those who prefer that life on Earth started on Earth, an alternative, also unproven hypothesis. This book updates the concept of panspermia in the light of new evidence on planet formation, molecular clouds, solar system motions, supernovae ejection mechanisms, etc. Thus, it is to be a book about newly understood prospects for the movement of life through space. The novel approach presented in this book gives new insights into the panspermia theory and its connection with planetary formation and the evolution of galaxies. This offers a good starting point for future research proposals about exolife and a better perspective for empirical scrutiny of panspermia theory. Also, the key to understanding life in the universe is to understand that the planetary formation process is convolved with the evolution of stellar systems in their galactic environment. The book provides the synthesis of all these elements and gives the readers an up-to-date insight on how panspermia might fit into the big picture. Audience Given the intrinsic interdisciplinary nature of the panspermia hypothesis the book will have a wide audience across various scientific disciplines covering astronomy, biology, physics and chemistry. Apart from scientists, the book will appeal to engineers who are involved in planning and realization of future space missions.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 592
Veröffentlichungsjahr: 2021
Ähnliche
Table of Contents
Cover
Title page
Copyright
Preface
References
Part I PHILOSOPHICAL ASPECTS OF PANSPERMIA
1 “On the Origin of Life”
2 Why We Should Take Interstellar Panspermia Seriously
2.1 Introduction
2.2 The Case for Interstellar Panspermia
2.3 Theoretical Consequences of Interstellar Panspermia
2.4 Conclusions
References
3 The Extended Continuity Thesis, Chronocentrism, and Directed Panspermia
3.1 Introduction: The Continuity as a Pre-Requisite for Scientific Grounding of Astrobiology
3.2 Versions and Resistance
3.3 Cultural Evolution and Directed Panspermia
3.4 Conclusion and Prospects
Acknowledgements
References
4 Life in the Milky Way: The Panspermia Prospects
4.1 Introduction
4.2 Three Levels of Habitability and Panspermia
4.3 Conclusions
Acknowledgements
References
Part II MICROORGANISMS AND PANSPERMIA
5 Planetary Protection: Too Late
5.1 Introduction
5.2 What is Planetary Protection
5.3 Extent of Earth Biosphere
5.4 Extension to Other Planetary Bodies
5.5 Backward Contamination
5.6 Interplanetary Exchange
5.7 Habitable Conditions for Interplanetary Micronauts
5.8 Conclusion
Appendix A
Appendix B
Appendix C
Acknowledgments
References
6 Microbial Survival and Adaptation in Extreme Terrestrial Environments— The Case of the Dallol Geothermal Area in Ethiopia
6.1 Introduction
6.2 Planetary Field Analog: The Case of the Dallol Geothermal Area
6.3 Life in Extreme Environments
6.4 Conclusion and Remarks on Panspermia
Acknowledgements
References
7 Escape From Planet Earth: From Directed Panspermia to Terraformation
Acknowledgements
References
Part III FORMATION AND EVOLUTION OF PLANETS: MATERIAL EXCHANGE PROSPECTS
8 Catalyzed Lithopanspermia Through Disk Capture of Biologically Active Interstellar Material
8.1 Introduction
8.2 Capture of Interstellar Planetesimals
8.3 Catalyzed Lithopanspermia
8.4 Conclusion and Discussion
Acknowledgements
References
9 Lithopanspermia at the Center of Spiral Galaxies
9.1 Introduction
9.2 The
Kepler
Transit Survey and the Distribution of Living Worlds
9.3 XUV Hydrodynamic Escape and the Formation of Habitable Evaporated Cores
9.4 Frequency of Exchange in High Stellar Densities
9.5 Detecting Panspermia
9.6 Concluding Remarks
References
10 Wet Panspermia
10.1 Introduction
10.2 Earth and Its Isotopic World: Geological and Environmental Implications
10.3 Quest for the Primordial Water Worlds
10.4 Looking for the Biotic Traces in Extraterrestrial Material
10.5 Ices of the Moon and Proposal of Earth-Induced Wet Panspermia in the Solar System
10.6 Implications for Other Planets of the Inner Solar System?
10.7 Conclusions
References
11 There Were Plenty of Day/Night Cycles That Could Have Accelerated an Origin of Life on Earth, Without Requiring Panspermia
Acknowledgement
References
12 Micrometeoroids as Carriers of Organics: Modeling of the Atmospheric Entry and Chemical Decomposition of Sub-Millimeter Grains
12.1 Micrometeorites and the Search for Life
12.2 White Soft Minerals
12.3 Atmospheric Entry Model
12.4 Results
12.5 The Role of Primordial Atmospheres
12.6 Conclusions
References
13 Dynamical Evolution of Planetary Systems: Role of Planetesimals
13.1 Introduction
13.2 Planetesimal Formation and Evolution
13.3 Transporting Mechanism in Later Stages of Planetary System Evolution
13.4 Conclusion
Acknowledgements
References
Part IV FURTHER PROSPECTS
14 A Survey of Solar System and Galactic Objects With Pristine Surfaces That Record History and Perhaps Panspermia, With a Plan for Exploration
14.1 Introduction
14.2 Recording Properties
14.3 Pristine Potential of Solar System Bodies
14.4 Prospects and Conclusions
Acknowledgements
References
15 The Panspermia Publications of Sir Fred Hoyle
Acknowledgements
References
Index
Also of Interest
End User License Agreement
Guide
Cover
Table of Contents
Title page
Copyright
Preface
Begin Reading
Index
Also of Interest
End User License Agreement
List of Illustrations
Chapter 3
Figure 3.1 A symbolic representation of the feedback created by directed pansper...
Chapter 4
Figure 4.1 Sketch of the levels of influences of matter and their inter-relation...
Chapter 5
Figure 5.1 Author (left) with colleagues in the class 100,000 cleanroom at the M...
Figure 5.2 Left: The very first photograph that Neil Armstrong took on the Moon:...
Figure 5.3 Left: Plotted orbits of all known inner Solar System asteroids as of ...
Figure 5.4 Left: Present-time factors for habitability of terrestrial planets. P...
Chapter 6
Figure 6.1 Location map of the Danakil Depression and the Dallol geothermal area...
Figure 6.2 Landsat 8 pan-sharpened RGB-321 color composite image (scene ID: LC81...
Figure 6.3 (a and b) Photographs of the Assale salt plain showing irregular poly...
Figure 6.4 Panoramic view (from southwest) of the Black Mountain. Note the whiti...
Figure 6.5 (a) Panoramic view of a field of sulfur and halite deposits associate...
Figure 6.6 Photographs of the mounds at the Dallol Hot Springs site. (a) Field o...
Figure 6.7 Photographs of terrace morphologies at the Dallol Hot Springs site. (...
Figure 6.8 (a) Active mushroom-like structures (field of view ca. 4 m). Reproduc...
Figure 6.9 (a) White halite salt rims (a few mm in thickness) forms as a result ...
Chapter 7
Figure 7.1 The TRAPPIST-1 exoplanets (labeled b through h), compared to Mercury,...
Figure 7.2 Breakthrough Starshot Lightsail nanocraft. (a). StarChip—a centimeter...
Figure 7.3 Artist’s impression of ‘Oumuamua (1I/2017 U1). Discovered on October ...
Chapter 8
Figure 8.1 Total number of captured planetesimals as a function of their size. S...
Chapter 9
Figure 9.1 Planet mean density
ρp
as a function of galactocentric distance
R
gc
. ...
Figure 9.2 Number of captured objects as a function of their velocities. Higher ...
Figure 9.3 Theoretical spatial density of rocky planets (
n
terr
) as a function of...
Figure 9.4 Spacetime topography of life-bearing planets for a case with the incl...
Chapter 11
Figure 11.1 Estimates for the date of LUCA seem to have settled down. From Table...
Chapter 12
Figure 12.1 Thermal curves of different entry scenarios related to a MgCO
3
micro...
Figure 12.2 Magnesium carbonate fraction occurrences at different altitudes.
Figure 12.3 Radiative and evaporative energy loss contributions during the atmos...
Figure 12.4 Grazing entry scenarios of MgCO
3
micrometeoroids.
Figure 12.5 Thermal curves of different entry scenarios related to a CaCO
3
micro...
Figure 12.6 Calcium carbonate fraction occurrences at different altitudes.
Figure 12.7 Grazing entry scenarios of CaCO
3
micrometeoroids.
Figure 12.8 Radiative and evaporative energy loss contributions during the atmos...
Figure 12.9 Thermal curves of different entry scenarios related to a FeCO
3
micro...
Figure 12.10 Iron carbonate fraction occurrences at different altitudes.
Figure 12.11 Radiative and evaporative energy loss contributions during the atmo...
Figure 12.12 Grazing entry scenarios of FeCO
3
micrometeoroids.
Figure 12.13 Thermal curves of different entry scenarios related to a CaSO
4
micr...
Figure 12.14 Anhydrous calcium sulfate fraction occurrences at different altitud...
Figure 12.15 Radiative and evaporative energy loss contributions during the atmo...
Figure 12.16 Atmospheric density effect (Figure from [12.80]).
Figure 12.17 A nitrogen molecule (blue) just before the impact with the crystal ...
Figure 12.18 Relative probabilities of the different events following the impact...
Figure 12.19 Thermal histories of a MgCO
3
(top left), CaCO
3
(top right), FeCO
3
(...
Figure 12.20 Thermal histories of a MgCO
3
(top left), CaCO
3
(top right), FeCO
3
(...
Figure 12.21 Thermal histories of a MgCO
3
(top left), CaCO
3
(top right), FeCO
3
(...
Chapter 13
Figure 13.1 Illustration of how a planetesimal from the planetesimal belt reache...
Figure 13.2 Amount of delivered water on planets in TRAPPIST-1 system in percent...
Chapter 14
Figure 14.1 Diameters of objects that have their escape velocities equal in magn...
List of Tables
Chapter 8
Table 8.1 Various parameters used for the estimation of the number of captured p...
Chapter 10
Table 10.1 Comparison between the composition of the lunar (Apollo 15) and terre...
Chapter 11
Table 11.1 Estimates for the date of LUCA.
Table 11.2 Data from [11.5]. Geological names from [11.21] for time points desig...
Chapter 12
Table 12.1
κ
′ values of magnesite, calcite, siderite, and anhydrite.
Table 12.2
κ
′ values of oxides.
Table 12.3
κ
′ values of gases.
Table 12.4
κ
′ values of primordial atmospheres.
Chapter 13
Table 13.1 Abundance of 18 most abundant elements relative to H, taken from [13....
Table 13.2 List of volatile materials for C, S, and M types of asteroids.
Pages
v
ii
iii
iv
xi
xii
xiii
xiv
1
3
4
5
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
53
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
119
120
121
122
123
124
125
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
267
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Astrobiology Perspectives on Life of the Universe
Series Editors: Richard Gordon and Joseph Seckbach
In his 1687 book Principia, Isaac Newton showed how a body launched atop a tall mountain parallel to the ground would circle the Earth. Many of us are old enough to have witnessed the realization of this dream in the launch of Sputnik in 1957. Since then our ability to enter, view and understand the Universe has increased dramatically. A great race is on to discover real extraterrestrial life, and to understand our origins, whether on Earth or elsewhere. We take part of the title for this new series of books from the pioneering thoughts of Svante Arrhenius, who reviewed this quest in his 1909 book The Life of the Universe as Conceived by Man from the Earliest Ages to the Present Time. The volumes in Astrobiology Perspectives on Life of the Universe will each delve into an aspect of this adventure, with chapters by those who are involved in it, as well as careful observers and assessors of our progress. Guest editors are invited from time to time, and all chapters are peer-reviewed.
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Planet Formation and Panspermia
New Prospects for the Movement of Life through Space
Edited by
Branislav Vukotić
Astronomical Observatory, Belgrade, Serbia
Richard Gordon
Gulf Specimen Marine Laboratory & Aquarium, Panacea, FL, USA and Wayne University, Detroit, MI, USA
and
Joseph Seckbach
The Hebrew University of Jerusalem, Israel
This edition first published 2021 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2021 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.
Wiley Global Headquarters111 River Street, Hoboken, NJ 07030, USA
For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com.
Limit of Liability/Disclaimer of WarrantyWhile the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials, or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read.
Library of Congress Cataloging-in-Publication Data
ISBN 978-1-119-64039-4
Cover image: Courtesy of NASACover design by Russell Richardson
Set in size of 11pt and Minion Pro by Manila Typesetting Company, Makati, Philippines
Printed in the USA
10 9 8 7 6 5 4 3 2 1
Preface
The panspermia hypothesis dates back to the works of ancient philosophers. In the 1800s, organics in meteorites were considered by the Swedish chemist Jacob Berzelius [1.3] [1.4] and later German physician Hermann E. Richter [1.15] speculated on the possibility of life transport by meteors. Lord Kelvin [1.9], discussed the possibility of panspermia in his Presidential Address to the British Association for the Advancement of Science. At the beginning of the next century, Swedish physicist/chemist Svante August Arrhenius (1908) presented his book on the panspermia theory [1.2]. There is a long history from before this time through the last century of claims of finding life in meteorites [1.6]. Astronomical sciences also developed significantly during this period to the point where we can observe gravitational waves from merging black holes, which was hardly imaginable just a few decades ago, and visualize black holes. With the discovery of many exoplanets astrobiology has matured as a scientific discipline. A tentative discovery of the intergalactic meteor particle in 2007 [1.1] and recent discoveries of an anomalous object ‘‘Oumuamua [1.11] and comet 2I/Borisov [1.8], that appear to have visited us from outside the Solar system, point out that our planet and its host star may not be an isolated island, in an otherwise lifeless universe. They are likely to exchange matter with the other stars from their vicinity as probably is the case with other stellar systems too, perhaps containing life. There is currently a bias that any such panspermia, if they exist, are prokaryotes [1.13] [1.16] or rugged, microscopic Eukaryotes [1.14].
In addition to transporting the physical bodies of microorganisms, another important aspect is the transport of biological information about these living systems. After all, the evolution of life on Earth is about altering the genetic code, either by natural or artificial means. Given that the organic matter, the building blocks for living organisms, is omnipresent in the universe, the aforementioned information might in some way be considered as the essence of life, at least in our current genocentric view of life [1.5]. The aspect of sending just the information signal in order to spread life is investigated in the visionary sci-fi novel “His Master’s Voice” by Polish writer Stanislaw Lem, first published in 1968 [1.10]. Contemporary with the beginning radio SETI searches [1.18], this offered a convergence point between sending and receiving SETI signals and the panspermia hypothesis. Information panspermia was later born in 2005 with the work of Vahe Gurzadyan [1.7].
In times when a number of exciting new discoveries are made and the new ones seem to be just around the corner, the millenia old panspermia hypothesis has not yet matured into a full fledged theory and some of its aspects might still not have been envisioned. Along the lines of scientific falsificationism, we can consider that no evidence against panspermia are found to date and that much of the controversy still remains [1.12]. The search is even more active in the opposite direction but still there is an evident lack of convincingly non-terrestrial microorganisms on Solar system bodies other than Earth. The recent experiments with micro-organisms exposed to space conditions at the International Space Station offer accumulating evidence that these organisms can withstand the harsh conditions of open space for long periods of time while preserving their biological potential. Even more, there are mounting concerns that human made space vehicles can spread life from our biosphere to other bodies of the Solar system, the most recent one being that the Israeli space mission that transported tardigrades to the Moon [1.17].
While panspermia is related to microorganisms and small scale processes on one end, on the other end, the transport of material depends on environmental conditions in galaxies. The evolution of galaxies depends on the interaction of galaxies within galaxy clusters and the overall evolution of matter in the universe. The galaxies are the main building blocks of our universe, analogous to cells in a human body. The stars and their planets are condensed from the clouds of galactic gas and dust that are rich in organics. The process of planetary formation is at the middle among the above stated scales that are relevant for panspermia. Starting from planetary formation, studies can go in either direction, to larger or smaller scales, to investigate phenomena that could spread life.
This collection of chapters incorporates studies from biology, astronomy and geology that investigate the possibility of panspermia, with most of them directly investigating phenomena related to the process of planetary formation. The processes described in these chapters permit the panspermia hypothesis, but empirical confirmation is still lacking at the level of our current knowledge. The basic aim of this book is to provoke readers to contemplate their respective research fields that are related to panspermia. For that matter it presents the basics of panspermia but also the advanced studies in the research fields presented. The chapters are comprehensible on a student level but at the same time they might be very interesting to experienced researchers. Possibly, some of them are already working on current and future space missions that may offer an empirical vindication of extra-terrestrial life transfer through the vastness of space.
Branislav Vukotić
Richard Gordon
Joseph Seckbach
September 1, 2021
References
[1.1] Afanasiev, V.L., Kalenichenko, V.V., Karachentsev, I.D., Detection of an intergalactic meteor particle with the 6-m telescope. Astrophys. Bull., 62, 4, 301–310, 2007.
[1.2] Arrhenius, S., Worlds in the Making; the Evolution of the Universe, Harper, New York, 1908.
[1.3] Berzelius, J.J., Analysis of the Alais meteorite and implications about life in other worlds. Ann. Chem. Pharm., 10, 134–135, 1834.
[1.4] Chyba, C.F., Extraterrestrial amino acids and terrestrial life. Nature, 348, 6297, 113–114, 1990.
[1.5] Gordon, R., Are we on the cusp of a new paradigm for biology? The illogic of molecular developmental biology versus Janus-faced control of embryogenesis via differentiation waves. BioSystems (Waves Fertilization, Cell Division Embryogenesis, Guest Editors: Jack Tuszynski, Luigia Santella & Richard Gordon), 203, 104367, 2021.
[1.6] Gordon, R. and McNichol, J., Recurrent dreams of life in meteorites, in: Genesis - In the Beginning: Precursors of Life, Chemical Models and Early Biological Evolution, J. Seckbach (Ed.), pp. 549–590, Springer, Dordrecht, 2012.
[1.7] Gurzadyan, V.G., Kolmogorov complexity, string information, panspermia, and the Fermi paradox. Observatory, 125, 1189, 352–355, 2005.
[1.8] Guzik, P., Drahus, M., Rusek, K., Waniak, W., Cannizzaro, G. and Pastor-Marazuela, I., Initial characterization of interstellar comet 2I/Borisov. Nat. Astron., 4, 53–57.
[1.9] Kelvin, L., On the Origin of Life. Excerpt. From the Presidential Address to the British Association for the Advancement of Science, held at Edinburgh, 1871, https://zapatopi.net/kelvin/papers/on_the_origin_of_life.html.
[1.10] Lem, S., His Master’s Voice, Northwestern University Press, Evanston, Illinois, USA, 1999.
[1.11] Loeb, A., Extraterrestrial: The First Sign of Intelligent Life Beyond Earth, Houghton Mifflin Harcourt, Boston. Massachusetts, USA, 2021.
[1.12] McNichol, J. and Gordon, R., Are we from outer space? A critical review of the panspermia hypothesis, in: Genesis - In the Beginning: Precursors of Life, Chemical Models and Early Biological Evolution, J. Seckbach (Ed.), pp. 591–619, Springer, Dordrecht, 2012.
[1.13] Ott, E., Kawaguchi, Y., Kölbl, D., Rabbow, E., Rettberg, P., Mora, M., Moissl-Eichinger, C., Weckwerth, W., Yamagishi, A., Milojevic, T., Molecular repertoire of Deinococcus radiodurans after 1 year of exposure outside the International Space Station within the Tanpopo mission. Microbiome, 8, 1, 150, 2020.
[1.14] Persson, D., Halberg, K.A., Jørgensen, A., Ricci, C., Møbjerg, N., Kristensen, R.M., Extreme stress tolerance in tardigrades: surviving space conditions in low earth orbit. J. Zool. Syst. Evol. Res., 49, 90–97, 2011.
[1.15] Raulin-Cerceau, F., Maurel, M.C., Schneider, J., From Panspermia to bioastronomy, the evolution of the hypothesis of universal life. Origins Life Evol. Biosphere, 28, 4-6, 597–612, 1998.
[1.16] Stan-Lotter, H., Survival of subsurface microbial communities over geological times and its implication for astrobiology, in: Model Ecosystems in Extreme Environments [MEET, Volume 2 in series: Astrobiology: Exploring Life on Earth and Beyond, series editors: Pabulo Henrique Rampelotto, Richard Gordon & Joseph Seckbach], J. Seckbach and P.H. Rampelott (Eds.), pp. 169–188, Elsevier B.V., Amsterdam, 2019.
[1.17] T., N., Israeli Beresheet Spacecraft Allegedly Brought Microscopic Organisms to the Moon, Possibly Taking Over, Tech Times, New York, USA, 2020, https://www.techtimes.com/articles/255393/20201227/israeli-beresheet-spacecraft-allegedly-brought-microscopic-organisms-moonpossibly-taking.htm.
[1.18] Wikipedia, Search for extraterrestrial intelligence, https://en.wikipedia.org/wiki/Search_for_extraterrestrial_intelligence,2020.
Part IPHILOSOPHICAL ASPECTS OF PANSPERMIA
1“On the Origin of Life”
By Lord Kelvin (William Thomson)
Excerpt. From the Presidential Address to the British Association for the Advancement of Science; held at Edinburgh in August, 1871 Reprinted in Kelvin’s Popular Lectures and Addresses, p. 132-205. (Bracketed additions are from reprint.)
[p. 197.]
Think now of the admirable simplicity with which Tait’s beautiful “sea-bird analogy,” as it has been called, can explain all [?] these phenomena.
The essence of science, as is well illustrated by astronomy and cosmical physics, consists in inferring antecedent conditions, and anticipating future evolutions, from phenomena which have actually come under observation. In biology the difficulties of successfully acting up to this ideal are prodigious. The earnest naturalists of the present day are, however, not appalled or paralysed by them, and are struggling boldly and laboriously to pass out of the mere “Natural History stage” of their study, and bring zoology within the range of Natural Philosophy. A very ancient speculation, still clung to by many naturalists (so much so that I have a choice of modern terms to quote in expressing it) supposes that, under meteorological conditions very different from the present, dead matter may have run together or crystallised or fermented into “germs of life,” or “organic cells,” or “protoplasm.” But science brings a vast mass of inductive evidence against this hypothesis of spontaneous generation, as you have heard from my predecessor in the Presidential chair. Careful enough scrutiny has, in every case up to the present day, discovered life as antecedent to life. Dead matter cannot become living without coming under the influence of matter previously alive. This seems to me as sure a teaching of science as the law of gravitation. I utterly repudiate, as opposed to all philosophical uniformitarianism, the assumption of “different meteorological conditions”—that is to say, somewhat different vicissitudes of temperature, pressure, moisture, gaseous atmosphere—to produce or to permit that to take place by force or motion of dead matter alone, which is a direct contravention of what seems to us biological law. I am prepared for the answer, “Our code of biological law is an expression of our ignorance as well as of our knowledge.” And I say yes: search for spontaneous generation out of inorganic materials; let any one not satisfied with the purely negative testimony of which we have now so much against it, throw himself into the inquiry. Such investigations as those of Pasteur, Pouchet, and Bastian are among the most interesting and momentous in the whole range of Natural History, and their results, whether positive or negative, must richly reward the most careful and laborious experimenting. I confess to being deeply impressed by the evidence put before us by Professor Huxley, and I am ready to adopt, as an article of scientific faith, true through all space and through all time, that life proceeds from life, and from nothing but life.
How, then, did life originate on the Earth? Tracing the physical history of the Earth backwards, on strict dynamical principles, we are brought to a red-hot melted globe on which no life could exist. Hence when the Earth was first fit for life, there was no living thing on it. There were rocks solid and disintegrated, water, air all round, warmed and illuminated by a brilliant Sun, ready to become a garden. Did grass and trees and flowers spring into existence, in all the fulness of ripe beauty, by a fiat of Creative Power? or did vegetation, growing up from seed sown, spread and multiply over the whole Earth? Science is bound by the everlasting law of honour, to face fearlessly every problem which can fairly be presented to it. If a probable solution, consistent with the ordinary course of nature, can be found, we must not invoke an abnormal act of Creative Power. When a lava stream flows down the sides of Vesuvius or Etna it quickly cools and becomes solid; and after a few weeks or years it teems with vegetable and animal life; which, for it, originated by the transport of seed and ova and by the migration of individual living creatures. When a volcanic island springs up from the sea, and after a few years is found clothed with vegetation, we do not hesitate to assume that seed has been wafted to it through the air, or floated to it on rafts. Is it not possible, and if possible, is it not probable, that the beginning of vegetable life on the Earth is to be similarly explained? Every year thousands, probably millions, of fragments of solid matter fall upon the Earth—whence came these fragments? What is the previous history of any one of them? Was it created in the beginning of time an amorphous mass? This idea is so unacceptable that, tacitly or explicitly, all men discard it. It is often assumed that all, and it is certain that some, meteoric stones are fragments which had been broken off from greater masses and launched free into space. It is as sure that collisions must occur between great masses moving through space as it is that ships, steered without intelligence directed to prevent collision, could not cross and recross the Atlantic for thousands of years with immunity from collisions. When two great masses come into collision in space it is certain that a large part of each is melted; but it seems also quite certain that in many cases a large quantity of debris must be shot forth in all directions, much of which may have experienced no greater violence than individual pieces of rock experience in a land-slip or in blasting by gunpowder. Should the time when this Earth comes into collision with another body, comparable in dimensions to itself, be when it is still clothed as at present with vegetation, many great and small fragments carrying seed and living plants and animals would undoubtedly be scattered through space. Hence and because we all confidently believe that there are at present, and have been from time immemorial, many worlds of life besides our own, we must regard it as probable in the highest degree that there are countless seed-bearing meteoric stones moving about through space. If at the present instant no life existed upon this Earth, one such stone falling upon it might, by what we blindly call natural causes, lead to its becoming covered with vegetation. I am fully conscious of the many scientific objections which may be urged against this hypothesis, but I believe them to be all answerable. I have already taxed your patience too severely to allow me to think of discussing any of them on the present occasion. The hypothesis that [some] life [has actually] originated on this Earth through moss-grown fragments from the ruins of another world may seem wild and visionary; all I maintain is that it is not unscientific, [and cannot rightly be said to be improbable.]
2Why We Should Take Interstellar Panspermia Seriously
Amedeo Balbi
Dipartimento di Fisica, Università degli Studi di Roma “Tor Vergata” Via della Ricerca Scientifica, Roma, Italy
Abstract
After a long period of neglect, the hypothesis of interstellar panspermia has gained new consideration in recent years, due to a series of theoretical and observational developments. In this chapter, I briefly outline why this possibility should not be dismissed, especially in regions of the Galaxy with higher stellar density than average. Furthermore, I give some motivations for taking the mechanism into account when developing theoretical models of the distribution of life in the Galaxy (such as in studies of the galactic habitable zone) and in drawing implications from the results of future searches for biosignatures in exoplanets. This theoretical work should be complemented by experimental studies, in order to assess the concrete feasibility of panspermia with higher confidence.
Keywords: Astrobiology, extraterrestrial life, galactic habitabile zone, biosignatures, interstellar panspermia
2.1 Introduction
The idea that biological material—and even living organisms—can be exchanged between planetary systems is more than one century old, but it has not been part of the mainstream discussion in astrobiology for long [2.28, 2.43]. Historically, skepticism on the early proposals of panspermia, put forward at the beginning of the 20th century [2.3], was at least in part motivated by an incorrect understanding of planetary formation mechanisms, which was dominated by the “catastrophic” theories of Buffon, Chamberlin, Moulton, and Jeans [2.9]. However, even many decades after such theories were abandoned, panspermia failed to regain a place in the scientific discourse.
This has changed recently, at least in the version of panspermia—more appropriately called “lithopanspermia”—which posits that life can travel across space carried by meteoroids and other minor bodies. There is now well-established evidence that rock fragments have indeed been exchanged between nearby planets in the Solar System, such as Mars and the Earth [2.32]. Available data on the survivability of radio-tolerant organisms in deep space, as well as experimental tests on hypervelocity impacts, make it conceivable that extremophiles trapped in rocks can be expelled by an inhabited planet and reach other locations unharmed [2.18, 2.19, 2.33]. This has led to speculation that nearby planets in the Solar System could have cross-contaminated in the past [2.30] and that other, more densely packed planetary systems, such as the one around TRAPPIST-1, might be even more conducive to the accidental spreading of life from one habitable location to another [2.20, 2.23]. The possible occurrence of panspermia within the Solar System would have obvious direct consequences for the problem of the origin of life on Earth.
Enlarging the scope to galactic scale, the observation of the first interstellar asteroid visiting the Solar System [2.27] has confirmed that the exchange of material between stellar systems is feasible. In light of this, the idea that life can be disseminated by natural processes over interstellar distances cannot be dismissed. In this short chapter, I will argue that the mere possibility of interstellar panspermia should be given careful consideration, as it would have relevant consequences on the assessment of galactic habitability and on the interpretation of future exoplanet observations.
2.2 The Case for Interstellar Panspermia
The possibility that panspermia could act over interstellar distances has been debated for at least two decades. Initial estimates of the probability that a rock ejected from Earth could be captured by another terrestrial planet in a different stellar system in the solar neighborhood were deemed too small to be relevant as a life-spreading mechanism [2.29]. Thus, interstellar panspermia was also dismissed as implausible. However, subsequent studies argued that such a conclusion was probably too pessimistic [2.45, 2.13, 2.46]. In fact, it was shown that the capture probability could increase in crowded environments, such as in star-forming clusters [2.2, 2.7], and can be significantly enhanced by interactions with binary systems [2.24].
Because the survivability of microorganisms in deep space depends on the shielding mechanism provided by the rocks, there is probably a minimal mass to life-carrying fragments for panspermia to work at interstellar distances, of order ~1–10 kg. If the typical survival time of microorganisms trapped in the rocks is τs, the fraction of surviving microorganisms after a travel time t can be modeled as P ∝ e-t/τs [2.13]. No exact estimate for τs exists, although values of order ~105 years or higher seem possible given favourable conditions. In this regard, we note that the assumption that microorganisms can only survive when shielded within rocks is rather conservative: more speculative scenarios can be envisioned, where microorganisms endure the vacuum of space without insolation and atmosphere (powered, for example, by slow chemical reactions or even long-lived radionuclides), leading to much larger values of τs. Whichever the case, by adopting this simple survival model and assuming a dynamical mechanism for the transfer of material, one can estimate the rate of life-bearing rocks impacting a terrestrial planet at any location in the Galaxy.
The possibility that interstellar panspermia played a role over the entire disk of the Milky Way is certainly not established conclusively, but it cannot be entirely dismissed either. Because of the different stellar densities at various locations, the effectiveness of the mechanism is not homogeneous over the whole Galaxy, and it might have been more important within specific subvolumes. In [2.5], we argued that the eventuality of lithopanspermia should be given special consideration for planets residing in the galactic bulge, where the high density of stellar systems might make the transfer more likely than in the disk (see also [2.8]). We made an initial estimate of the efficiency of panspermia in the bulge by adopting the model outlined in [2.29, 2.2] for the rate of life-bearing rocks impacting a terrestrial planet in another stellar system
where v is the relative velocity of rocks with respect to the stars, nL is the number density of life-bearing rocks, and σ is the impact cross-section. The latter can be computed as the product of the capture cross-section from a stellar system, σc, and the probability that a rock impacts a terrestrial planet in the system once is captured, Pimpact. Plausible values for σc are in the range 0.01–0.05 AU2 [2.29] and are expected to vary based on the average stellar velocity dispersion, orbital configurations and multiplicity of the stellar and planetary systems, ejection velocity, rock size distribution, and so on. In our analysis, we adopted the values σc = 0.025 AU2 and Pimpact = 10–4 from [2.29]: these are probably conservative in general, and in particular with respect to the conditions in the bulge. In fact, the value adopted for σc applies to planetary systems with a Jupiter-type planet in a Jupiter-like orbit. However, only ~10% of all systems meet this criterion. As already mentioned, binary star systems (that make up roughly 40% of all stars) have a much higher cross-section [2.24, 2.13]. Similarly, the capture rate can be enhanced in systems that contain massive hot Jupiters or brown dwarfs, both of which could have habitable exomoons. As an illustration, using the fit for σc from [2.2] and assuming a velocity dispersion ~120 km/s for stars in the bulge [2.44] would result in a value σc = 0.045 AU2.
The number density of life-bearing rocks per year can be assumed to be proportional to the star density, nL = γnt, with γ~15/yr [2.2]. Then, the typical diffusion timescale for life between stellar systems in the galactic bulge can be found by τ = 1/г and is
If indeed life “colonizes” a suitable planet after transport, tD represents the typical timescale for the evolution of the fraction of inhabited planetary systems in the bulge. Adopting a realistic model for the stellar density n leads one to conclude that, all over the bulge, even a single inhabited planet might in principle spread life to all other suitable stellar systems in a time ~1 Gyr, much smaller than the age of the Galaxy [2.5].
While this is not a full-fledged examination of the problem, it gives some support to the idea that the galactic bulge could be seeded with biological material much more efficiently than the solar neighborhood. A possible hindrance, in this respect, is the effect of the radiation environment, which is certainly harsher near the galactic center than in the disk [2.4, 2.5], as well as the higher risk of potentially sterilizing events such as supernovae or tidal disruption events [2.35]. Even if life is not completely wiped out, ionizing radiation can still influence planetary habitability by enhancing the rate of atmospheric mass loss (see, e.g., [2.34]). Furthermore, it has been argued that a high level of ultraviolet radiation could suppress the formation of terrestrial planets via protoplanetary grain evaporation [2.1]. However, strong ultraviolet doses could also have beneficial effects, for example, by increasing the rate of prebiotic synthesis of biomolecular building blocks [2.25].
It should also be noted that there might be safer routes for microorganisms if the transfer happens indirectly, for example, through cometary bodies that are subsequently captured into a protoplanetary disc: this mechanism could in principle spread life through the Galaxy at a rate of ~5 kpc Gyr–1, covering the entire Galaxy in just a few Gyr [2.42], a short time compared to the age of the oldest stars in the Milky Way, 13.41 ± 0.54 Gyr [2.37].
2.3 Theoretical Consequences of Interstellar Panspermia
The status of present knowledge does not warrant a conclusive position on the actual feasibility of interstellar panspermia. However, the previous discussion, although sketchy and incomplete, suggests that we keep an open mind. Adopting an agnostic stance in light of poor evidence is the most rational course of action. At the same time, there is by now plenty of motivations to look more closely into the issue than was done in the past, both experimentally and theoretically.
In particular, even without committing to a specific scenario, it is interesting to explore what would be the theoretical consequences of considering interstellar panspermia as a possible ingredient when modeling the distribution of life on galactic scales. There are at least two aspects that should deserve close attention in future studies.
The first is to include a panspermia mechanism of some sort in studies of galactic habitability. The existence of a galactic habitable zone (GHZ) was first pointed out in pioneering studies almost two decades ago [2.14, 2.22]. While the concept was later refined and investigated in more detail, with varying degrees of overlap among different assumptions and conclusions (see, e.g., [2.36, 2.41, 2.11, 2.15, 2.16, 2.31]), the inclusion of panspermia in GHZ models is the exception rather than the norm [2.10].
So far, the conventional approach to GHZ has focused mainly on identifying locations (and epochs) where the formation of terrestrial planets can preferentially take place, and on assessing the risk for life in such locations due to possible nearby catastrophic events, such as supernovae explosions. Such an approach might turn out to be too conservative if interstellar panspermia can take place. One can envision the existence of a trade-off between sterilizing events and the possible survival of life by interstellar migration, such that some equilibrium point is reached, depending on the typical time-scales of such competing processes. In fact, as pointed out in [2.5], even galactic locations that traditionally were deemed too harsh to be habitable, such as the bulge, might benefit from the greater facility for life to leave its original abode, spreading elsewhere. Attempts to model the possible distribution of inhabited planets should take this aspect into due consideration, especially for the inner region of the Galaxy. More generally, any measure of the overall propensity of the Milky Way to host life should not overlook the fact that quick migration to safer locations could happen during the interval between extinctions events, thereby enlarging the boundary of the GHZ well beyond what has been deemed possible so far.
As a result, once panspermia is factored in, the qualitative features of the GHZ might be rather different from what is generally deduced. For example, the galactic bulge would have the highest number of potential locations for abiogenesis (provided that the formation of habitable planets is not too suppressed with respect to the disk) and, at the same time, the highest predisposition to panspermia. If we use as a reference the typical timescales of abiogenesis and biological evolution on Earth, there would be enough time for life to appear repeatedly on planets in the bulge between sterilizing events [2.5]. Thus, the bulge might be the most likely abode for microbial life (especially if high metallicity favours biochemistry) and act as a “source” of interstellar panspermia, seeding the outer regions of the galaxy, where conditions are more conducive to prolonged habitability and, therefore, to the evolution of complex organisms. This sort of radial gradient in life’s complexity, from the inner regions toward larger galactocentric distances, might even in principle be testable in the distant future.
In light of these considerations, it can be argued that, despite all the big uncertainties surrounding the problem, interstellar panspermia should, in principle, be treated on a par with other processes that are customarily included in GHZ models, but whose exact role is still unresolved, such as the biological effect of ionizing radiation or the dependence of terrestrial planet formation on stellar metallicity.
The second potentially important consequence of taking interstellar panspermia seriously has to do with the interpretation of future observations. Over the next couple of decades, there will be realistic prospects for detecting (or at least looking for) spectroscopic signatures of biological activity (“biosignatures”, for short) on nearby exoplanets [2.38, 2.17, 2.12, 2.26]. It has been suggested that the imprint of panspermia could be detected in the statistical correlation properties of exoplanetary biosignatures [2.21]. This is an interesting prospect, although definitely not around the corner. More relevant, in the near term, is how the possibility of panspermia can weaken the conclusions that can be inferred from the detection of one (or few) biosignatures in future exoplanetary surveys.
In [2.6], we used a Bayesian framework to show that even a single unambiguous detection of biosignatures in the vicinity of the Solar System, in a survey of the extent attainable in the next decades (i.e., less than 100 light years), would radically alter our prior credence on the frequency of life in the Galaxy, leading even an initially skeptical or pessimistic observer to conclude that inhabited planets are extremely common (of order 105 in the whole Milky Way). However, we also showed that allowing for the possibility of panspermia would substantially weaken such a conclusion.
A similar caveat is well-known when searching for life in the Solar System, where possible cross-contamination among terrestrial planets can result in the impossibility of firmly establishing independent abiogeneses (see, e.g., [2.39], where the panspermia hypothesis is discussed in the context of the recent claim for a possible biosignature, phosphine, on Venus). If interstellar panspermia is indeed possible, and if life can survive and adapt in a different habitable location within a relatively short time-scale after the transfer, there will be an enhanced probability that an exoplanet is inhabited if a nearby planet is inhabited as well: thus, the probability that two planets simultaneously display biosignatures will depend on their relative distance and on a typical length scale. By treating this length scale as a free parameter, and adopting a generic correlation model, we showed that detecting a biosignature would not allow us, in itself, to draw strong conclusions on the frequency of life in the Galaxy, when observing a sample of limited extent [2.6].
In other words, if interstellar panspermia is feasible, finding life in a nearby exoplanet would not exclude the possibility that we live in a cluster of correlated inhabited worlds, surrounded by volumes where life is uncommon. In the most extreme case, i.e., when the radius surveyed is smaller than the distance over which panspermia could act, discovering biosignatures in another stellar system would result in no net gain in the knowledge of the overall distribution and frequency of life in the Galaxy.
This, of course, is not the end of the story. On the contrary, it only highlights the necessity of further, more detailed theoretical work. As a final pointer in this direction, it should be noted that, in the previous discussion, it was implicitly assumed that panspermia acted on planets which originated and remained in a common galactic environment—i.e., at approximately constant relative distance. However, when one takes the complex behavior of stellar orbits into account (including, for example, phenomena like radial diffusion, secular increases in amplitude of vertical oscillations, etc.), there is no guarantee that this is the case. In fact, there are intriguing hints that even the Solar System went through a significant radial displacement from the inner galactic disk, since its formation [2.40]. Therefore, unless the age and history of planetary systems are known to sufficient accuracy that they can be connected to the dynamical properties of the Galaxy, any conclusion on the occurrence of panspermia drawn from the detection of correlated biosignatures would be weakened. This reinforces the need for embedding the study of planetary habitability, and the interpretation of future searches for life beyond Earth, in the wider galactic context.
2.4 Conclusions
I have briefly outlined some of the reasons that should suggest a careful examination of the feasibility of interstellar panspermia. If transfer of microscopic life across stellar systems has been an active mechanism over the course of galactic history, the implications cannot be overemphasized. Just to name the most obvious repercussion: if the exchange of dust and rocks had a role in disseminating not only biological building blocks but also living organisms across the Galaxy, the whole question of the typical timescale of abiogenesis would have to be completely reconsidered (and, therefore, prior assumptions on the frequency of life beyond Earth should be changed accordingly). Also, while the detection of life outside the Solar System would be a momentous discovery, the mere possibility that its origin and distribution can be correlated among nearby stellar systems would drastically alter the broader consequences of such a finding.
For this reason, more attention should be given in the future to the possibility of lithopanspermia as a viable mechanism over interstellar distances. Ideally, one would want to have strong reasons to either admit or refute the possibility of interstellar panspermia before evaluating the results of future observations, so as to choose the right prior when interpreting possible biosignatures detections. From a theoretical point of view, this should imply a careful examination of effective dynamical routes (and of travel timescales) for the transfer of life-carrying rocks across space, including various factors that have been neglected in previous studies, such as the mixing of stellar orbits, or the enhanced capture cross-section due to inhomogeneities in the stellar distribution. Also, as mentioned previously, the result of such analyses should inform the construction of future models of the GHZ, where the interstellar transfer of life should be included as an additional process, in competition with catastrophic astrophysical events.
In parallel with such theoretical work, independent experimental studies would be crucial to assess the feasibility of the various processes involved. This should include, for example, continuing and expanding the investigation of the survivability of organisms in deep space, conducting in vivo experiments of hypervelocity impacts, and examining pristine samples of rocks from the early epochs of the Solar System. There are also good chances of observing more interstellar asteroids in the Solar System, which would result in refined estimates of the amount of material that can be transferred between stars. This would also open the exciting prospect of investigating the composition of rocks of extrasolar provenance, either remotely, through spectroscopic studies, or, in the more distant future, in situ, with dedicated space probes. All in all, evaluating the plausibility of interstellar panspermia should be one of the top priorities of both theoretical and experimental astrobiology in the near future.
References
[2.1] Adams, F.C., Hollenbach, D., Laughlin, G., Gorti, U., Photoevaporation of Circumstellar Disks Due to External Far-Ultraviolet Radiation in Stellar Aggregates. Astrophys. J., 611, 360–379, 2004.
[2.2] Adams, F.C. and Spergel, D.N., Lithospanspermia in Star-Forming clusters. Astrobiology, 5, 497–514, 2005.
[2.3] Arrhenius, S., Panspermy: the transmission of life from star to star. Sci. Am., 9, 196, 1907.
[2.4] Balbi, A. and Tombesi, F., The habitability of the Milky Way during the active phase of its central supermassive black hole. Sci. Rep., 7, 1, #16626, 2017.
[2.5] Balbi, A. and Grimaldi, C., Quantifying the information impact of future searches for exoplanetary biosignatures. Proc. Natl. Acad. Sci., 117, 35, 21031–21036, 2020.
[2.6] Balbi, A., Hami, M., Kovačević, A., The Habitability of the Galactic Bulge. Life, 10, 8, 132, 2020.
[2.7] Belbruno, E., Moro-Martín, A., Malhotra, R., Savransky, D., Chaotic Exchange of Solid Material Between Planetary Systems: Implications for Lithopanspermia. Astrobiology, 12, 754–774, 2012.
[2.8] Chen, H., Forbes, J.C., Loeb, A., Habitable Evaporated Cores and the Occurrence of Panspermia Near the Galactic Center. Astrophys. J. Lett., 855, 1, L1, 2018.
[2.9] Dick, S.J., The Biological Universe: The Twentieth-Century Extraterrestrial Life Debate and the Limits of Science, Cambridge University Press, Cambridge, 1996.
[2.10] Đošović, V., Vukotić, B., Ćirković, M.M., Advanced aspects of Galactic habitability. Astron. Astrophys., 625, A98, 2019.
[2.11] Forgan, D., Dayal, P., Cockell, C., Libeskind, N., Evaluating galactic habitability using high-resolution cosmological simulations of galaxy formation. Int. J. Astrobiology, 16, 1, 60–73, 2017.
[2.12] Fujii, Y., Angerhausen, D., Deitrick, R. et al., Exoplanet Biosignatures: Observational Prospects. Astrobiology, 18, 739, 2018.
[2.13] Ginsburg, I., Lingam, M., Loeb, A., Galactic Panspermia. Astrophys. J., 868, 1, L12, 2018.
[2.14] Gonzalez, G., Brownlee, D., Ward, P., The Galactic Habitable Zone: Galactic Chemical Evolution. Icarus, 152, 185–200, 2001.
[2.15] Gowanlock, M.G., Patton, D.R., McConnell, S.M., A model of habitability within the Milky Way galaxy. Astrobiology, 11, 855–873, 2011.
[2.16] Gowanlock, M.G. and Morrison, I.S., The Habitability of Our Evolving Galaxy, in: Habitability of the Universe Before Earth, R. Gordon and A.A. Sharov (Eds.), 2018, series: Astrobiology: Exploring Life on Earth and Beyond, P. H. Rampelotto, J. Seckbach, R. Gordon (Eds.), Elsevier B.V., Amsterdam, 149.
[2.17] Grenfell, J.L., A review of exoplanetary biosignatures. Phys. Rep., 713, 1–17, 2017.
[2.18] Horneck, G., Stöffler, D., Ott, S., Hornemann, U., Cockell, C.S., Moeller, R., Meyer, C., de Vera, J.-P., Fritz, J., Schade, S., Artemieva, N.A., Microbial rock inhabitants survive hypervelocity impacts on mars-like host planets: First phase of lithopanspermia experimentally tested. Astrobiology, 8, 1, 17–44, 2008.
[2.19] Horneck, G., Klaus, D.M., Mancinelli, R.L., Space Microbiology, Microbiology and Molecular Biology Reviews. Am. Soc. Microbiol., 74, 1, 121–156, 2010.
[2.20] Krijt, S., Bowling, T.J., Lyons, R.J., Ciesla, F.J., Fast Litho-panspermia in the Habitable Zone of the TRAPPIST-1 System. Astrophys. J., 839, 2, #L21, 2017.
[2.21] Lin, H.W. and Loeb, A., Statistical signatures of panspermia in exoplanet surveys. Astrophys. J. Lett., 810, 1, #L3, 2015.
[2.22] Lineweaver, C.H., Fenner, Y., Gibson, B.K., The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way. Science, 303, 5654, 59–62, 2004.
[2.23] Lingam, M. and Loeb, A., Enhanced interplanetary panspermia in the TRAPPIST-1 system. Proc. Natl. Acad. Sci. U.S.A., 114, 26, 6689–6693, 2017.
[2.24] Lingam, M. and Loeb, A., Implications of Captured Interstellar Objects for Panspermia and Extraterrestrial Life. Astron. J., 156, 5, 193, 2018.
[2.25] Lingam, M., Ginsburg, I., Bialy, S., Active Galactic Nuclei: Boon or Bane for Biota? Astrophys. J., 877, 1, 62, 2019.
[2.26] Madhusudhan, N., Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects. Annu. Rev. Astron. Astrophys., 57, 617, 2019.
[2.27] Meech, K.J., Weryk, R., Micheli, M., Kleyna, J.T., Hainaut, O.R., Jedicke, R., Wainscoat, R.J., Chambers, K.C., Keane, J.V., Petric, A., Denneau, L., Magnier, E., Berger, T., Huber, M.E., Flewelling, H., Waters, C., SchunovaLilly, E., Chastel, S., A brief visit from a red and extremely elongated interstellar asteroid. Nature, 552, 7685, 378–381, 2017.
[2.28] Melosh, H.J., The rocky road to panspermia. Nature, 332, 687–688, 1988.
[2.29] Melosh, H.J., Exchange of meteorites (and life?) between stellar systems. Astrobiology, 3, 1, 207–215, 2003.
[2.30] Mileikowsky, C., Cucinotta, F.A., Wilson, J.W., Gladman, B., Horneck, G., Lindegren, L., Melosh, J., Rickman, H., Valtonen, M., Zheng, J.Q., Natural Transfer of Viable Microbes in Space: 1. From Mars to Earth and Earth to Mars. Icarus, 145, 2, 391–427, 2000.
[2.31] Morrison, I.S. and Gowanlock, M.G., Extending Galactic Habitable Zone Modeling to Include the Emergence of Intelligent Life. Astrobiology, 15, 8, 683–696, 2015.
[2.32] Nyquist, L.E., Bogard, D.D., Shih, C.-Y., Greshake, A., Stöffler, D., Eugster, O., Ages and Geologic Histories of Martian Meteorites. Space Sci. Rev., 96, 105–164, 2001.
[2.33] Onofri, S., de la Torre, R., de Vera, J.-P., Ott, S., Zucconi, L., Selbmann, L., Scalzi, G., Venkateswaran, K.J., Rabbow, E., Sánchez, I., Francisco, J., Horneck, G., Survival of rock-colonizing organisms after 1.5 years in outer space. Astrobiology, 12, 5, 508–516, 2012.
[2.34] Owen, J.E., Atmospheric Escape and the Evolution of Close-in Exoplanets. Annu. Rev. Earth Planet. Sci., 47, 1, 67–90, 2019.
[2.35] Pacetti, E., Balbi, A., Lingam, M., Tombesi, F., Perlman, E., The Impact of Tidal Disruption Events on Galactic Habitability. Mon. Notices R. Astron. Soc., 498, 3, 3153–3157, 2020.
[2.36] Prantzos, N., On the “galactic habitable zone”. Space Sci. Rev., 135, 313–322, 2008.
[2.37] Savino, A., Koch, Z., Prudil, A., Kunder, A., Smolec, R., The Age of the Milky Way Inner Stellar Spheroid from RR Lyrae Population Synthesis. Astron. Astrophys., 641, A96, 2020.
[2.38] Seager, S., The future of spectroscopic life detection on exoplanets. Proc. Natl. Acad. Sci. U.S.A., 111, 35, 12634–12640, 2014.
[2.39] Siraj, A. and Loeb, A., Transfer of Life Between Earth and Venus with Planet-Grazing Asteroids. ArXiv:2009.09512, 2020, https://arxiv.org/pdf/2009.09512.pdf.
[2.40] Tsujimoto, T. and Baba, J., Remarkable Migration of the Solar System from the Innermost Galactic Disk; a Wander, a Wobble, and a Climate Catastrophe on the Earth. Astrophys. J., 904, 2, #137, 2020.
[2.41] Vukotić, B., Steinhauser, D., Martinez-Aviles, G., Ćirković, M.M., Micic, M., Schindler, S., “Grandeur in this view of life”: N-body simulation models of the Galactic habitable zone. Mon. Notices R. Astron. Soc., 459, 3512–3524, 2016.
[2.42] Wallis, M.K. and Wickramasinghe, N.C., Interstellar transfer of planetary microbiota. Mon. Notices R. Astron. Soc., 348, 1, 52–61, 2004.
[2.43] Wesson, P.S., Panspermia, Past and Present: Astrophysical and Biophysical Conditions for the Dissemination of Life in Space. Space Sci. Rev., 156, 1–4, 239–252, 2010.
[2.44] Zhu, W., Udalski, A., Novati, S.C., Chung, S.-J., Jung, Y.K., Ryu, Y.-H., Shin, I.-G., Gould, A., Lee, C.-U., Albrow, M.D., Yee, J.C., Han, C., Hwang, K.-H., Cha, S.-M., Kim, D.-J., Kim, H.-W., Kim, S.-L., Kim, Y.-H., Lee, Y., Park, B.-G., Pogge, R.W., KMTNet Collaboration, Poleski, R., Mróz, P., Pietrukowicz, P., Skowron, J., Szymański, M.K., KozLowski, Ulaczyk, K., Pawlak, M., OGLE Collaboration, Beichman, C., Bryden, G., Carey, S., Fausnaugh, M., Gaudi, B.S., Henderson, C.B., Shvartzvald, Y., Wibking, B., Spitzer Team, Toward a Galactic Distribution of Planets. I. Methodology and Planet Sensitivities of the 2015 High-cadence Spitzer Microlens Sample. Astron. J., 154, 5, #210, 2017.
[2.45] Zubrin, R., Interstellar panspermia reconsidered. J. Br. Interplanet. Soc., 54, 7–8, 262–269, 2001.
[2.46] Zubrin, R., Exchange of material between solar systems by random stellar encounters. Int. J. Astrobiology, 19, 1, 43–48, 2019.
Email: [email protected]
3The Extended Continuity Thesis, Chronocentrism, and Directed Panspermia
Milan M. Ćirković
Astronomical Observatory of Belgrade, Belgrade, Serbia
Abstract
