22
ASTROBIOLOGY ORIGINS FROM THE BIG-BANG TO CIVILISATION
ASTROBIOLOGY ORIGINS FROM THE BIG-BANG TO CIVILISATION
THE INTERNATIONAL ORGANISING COMMITTE HUMBER TO CAMPlNS, University of Arizona and Research Corporation, Tucson,
USA IGNASI CASANOVA, Universitat Politecnica de Catalunya, Barcelona, Spain
FRANK DRAKE, Seti Institute, Mountain View USA ANTONIO LAZCANO, Universidad Nacional Autonoma de Mexico, Mexico
ULISES MOULINES, Institutfuer Philosoph ie, Logik und Wissenschaftstheorie LudwigMaximilians- Universitaet Muenchen, Germany
RAFAEL NAVARRO-GONZALEZ, Universidad Nacional Autonoma de Mexico, Mexico ALICIA NEGRON-MENDOZA, Universidad Nacional Autonoma de Mexico, Mexico
ADRIANA c. OCAMPO, NASA Headquarters, Washington D.C. USA YAREMI RIVERO (Coordinator, visit of the astronaut), Lyndon Johnson Space Center,
Houston, USA JUAN G. ROEDERER, University of Alaska-Fairbanks, USA.
LOCAL COMMITTEE GUSTAVO BRUZUAL, Centro de Investigaciones de Astronomfa, Merida
MARIO l. CAICEDO, Universidad Simon Bo[(var, Caracas ELINOR CALLAROTTI, Universidad Simon Bolivar, Caracas GREGORIO DRAYER, Universidad Simon Bolivar, Caracas
MARTHA ELt,NA GALA vis, Universidad Metropolitana, Caracas ERNESTO MAl'Z VALLENILLA, CENIT, (IDEA), Caracas
CESAR MENDOZA BRICENO, Centro de Astroflsica Teorica, Merida HECTOR RAGO, Grupo de Ffsica TeoricaiCentro de Astroflsica, ULA, Merida
TOMAS REVILLA, Escuela de Biologfa, Facultad de Ciencias, Universidad Central de Venezuela, Caracas
GLORIA VILLEGAS, Centro de Biociencias, (IDEA), Caracas.
SPONSORS International Centre for Theoretical Physics
International Centre for Genetic Engineering and Biotechnology Universidad Simon Bolivar NASA Headquarters,
European Space Agency, TALVEN Programme, (Delegacion Permanente de Venezuela ante la
UNESCO) The SET! Institute,
Centro Latinoamericano de Fisica, The Third World Academy of Sciences,
Academia de Ciencias Fisicas, Matematicas y Naturales, Red Latinoamericana de Biologia
The Planetary Society, The Latin American Academy of Sciences (Fondo ACAL).
Alberto Vollmer Foundation, Inc Fundaci6n J Oro, Associated to the Catalonian Research Foundation
Red Latinoamericana de Astronomia Colegio Emil Friedman
ASTROBIOLOGY
ORIGINS FROM THE BIG-BANG TO CIVILISATION
Proceedings of the Iberoamerican School of Astrobiology Caracas, Venezuela,
28 November- 8 December, 1999
Editedby
JULIĂN CHELA-FLORES, The Abdus Salam International Centre for Theoretical Physics, Italy and
Instituto de Estudios Avanzados (IDEA), Venezuela,
GUILLERMO A. LEMARCHAND, Instituto Argentino de Radioastronomia (CONICET), and
Centro de Estudios Avanzados, Universidad de Buenos Aires, Argentina
and
JOHNORO, Department of Biochemical and Biophysical Sciences
University of Houston, Houston, TX 77204-5934, USA.
SPRINGER SCIENCE+BUSINESS MEDIA, B.V.
Library of Congress Cataloging-in-Publication Data
ISBN 978-94-010-5865-0 ISBN 978-94-011-4313-4 (eBook) DOI 10.1007/978-94-011-4313-4
Printed on acid-free paper
Cover (illustration European Space Agency.): An artist's impression of "Huygens descend -stages on Titan". Cassini/Huygens is a NASA/ESA mission to the Saturnian System. The spacecraft consists of the NASA Saturn Orbiter and the detachable ESA Huygens Probe designed to explore the atmosphere of Titan, Saturn's largest moon. Within the context of chemical evolution and planetary science the mission, as well as Titan, were discussed during
the School. The reader is referred to pp. xxii, 85-87, 158-159, 277 and 307.
Photograph on page (v): Curtsey of The Abdus Salam ICTP Archives.
All Rights Reserved © 2000 Springer Science+Business Media Dordrecht
Originally published by Kluwer Academic Publishers in 2000
No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical,
incIuding photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner.
Dedicated to
Frank Drake
on the occasion of his 70th birthday
FRANK DRAKE
A biographical sketch
Dr. Frank Drake is Chairman of the Board of Trustees of the SETI Institute and provides
overall direction for research. In 1960, as a staff member of the National Radio
Astronomy Observatory, he conducted the first radio search for extraterrestrial
intelligence. The original efforts went under the name of Project Ozma after the Princess
in L. Frank Baum's story "Ozma of Oz". Four decades later, with the support by data
from many independent projects world-wide and the new evidence for the existence of
other planetary systems, the search for extraterrestrial life is an integral part of the new
science of astrobiology.
He is a member of the National Academy of Sciences where he chaired the Board
of Physics and Astronomy of the National Research Council (1989-92). He is a former
president of one of the world's leading astronomical organisations, the Astronomical
Society of the Pacific. He was a Professor of Astronomy at Cornell University (1964-
84) and served as the Director of the Arecibo Observatory. He is currently a Professor of
Astronomy and Astrophysics at the University of California at Santa Cruz where he also
served as Dean of Natural Sciences (1984-88).
PREFACE ix
The proposal of the School was made in 1998 to three institutions, which responded
enthusiastically: The Abdus Salam International Centre for Theoretical Physics
(ICTP), its main co-sponsor, the International Centre for Genetic Engineering and
Biotechnology, both in Trieste, Italy, and the Chancellor's Office, Universidad Simon
Bolfvar (USB). The secretarial and logistic support was provided in Trieste by the
ICTP and in Caracas by USB and the IDEA Convention Center.
In addition the event was generously supported by the following institutes,
agencies, foundations and academies: NASA Headquarters, European Space Agency,
TALVEN Programme, (Delegacion Permanente de Venezuela ante la UNESCO), The
SETI Institute, Centro Latinoamericano .de Ffsica, The Third World Academy of
Sciences, Academia de Ciencias Ffsicas, Matematicas y Naturales, Red Latinoamericana
de Biologfa, The Planetary Society, The Latin American Academy of Sciences (Fondo
ACAL), Alberto Vollmer Foundation, Inc, Fundacion J. Oro, Associated to the
Catalonian Research Foundation, Red Latinoamericana de Astronomfa and Colegio
Emil Friedman.
A total of 36 lectures were delivered by 20 lecturers, of which 14 were from
the following countries: Argentina, Mexico, Italy, Spain and the USA. Six lecturers
were from the host country. In addition there were 5 chairpersons from the host country
that were not participants; two participants acted as chairpersons (Pedro Benitez and
Tomas Revilla).
The School brought together 125 participants, which included some of the
leading researchers in the subfields of Astrobiology. There were 18 participants form:
Argentina, Colombia, Cuba, Mexico, Spain, Uruguay and the USA. The host country
was represented by 82 participants registered during the conference, of which 33 had
previously registered in Trieste. In addition to the lectures the participants contributed
16 oral presentations of their posters (ten minutes were assigned to each of the
participants that presented posters).
The media was represented by 3 participants from the host country. The event
was also consistently well represented by the national press. Another important
x
activity of lAS A was the following round-table: Music of the Spheres: Would other
intelligence also exhibit "artistic creativity?". Juan G. Roederer and Guillermo A.
Lemarchand acted as moderators with the participation of: Jacobo Borges, Diana
Arismendi, Irene McKinstry de Guinand and Julian Chela-Flores.
Public lectures were delivered by Professor Frank Drake, Professor Juan Or6
and Garrett E. Reisman a NASA Astronaut Candidate (Mission Specialist). An event
that was particularly appreciated by the participants was a Special Session on Solar
System Exploration in collaboration with The Planetary Society (TPS) and Direcci6n
de Servicios Multimedia de la Universidad Sim6n Bolfvar.1t was timed so as to make a
live Internet link-up with Planetfest in Pasadena, California on the occasion of the
Mars lander in the Martian South Pole. The collaboration of Lic. Gregorio Drayer in
the coordination of the event is gratefully acknowledged.
In spite of the fact that the lander was lost, the live contact with Planetfest and
telephone connection for 45 minutes (due to the generous support of the Planetary
Society) with an expert on Mars research (Dr. Christopher McKay) was a very
instructive experience for all the School The counselling and very constructive
initiatives of the TPS Executive Director, Dr. Louis Friedman were fundamental for
this event.
In Caracas we are particularly grateful to Chancellor Freddy Malpica and the
Chancellor's Office, without whose support this activity would not have taken place.
Our particular thanks to Ms. Nancy Padilla, who acted as the Caracas School Secretary.
Her helpful, friendly initiatives contributed significantly to the success of IASA. The
whole team of Lic. Rebeca L6pez de Alvarez, namely, Ms. Alicia de Armas, Beatriz
Troconis and Mariana Walker, provided essential aspects towards the improvement of
the School.
At the IDEA Convention Center, we would like to thank the team headed by
Lic. Ram6n Garriga; in particular, Mr. Luis Gonzalez, with the support of Ms Dayana
Barreto, acted efficiently as Administrator in Charge of IASA for the whole duration of
the School organisation (two years).
xi
In particular, we should highlight the generous and always helpful, critical
advice and collaboration of Ms. Pilar Martinez, Secretary of the Latin American
Academy of Sciences.
In Italy, special thanks are due to the ICTP administrative staff, particularly
Ms. E. Brancaccio, who acted as the School Secretary in Trieste. We would like to
acknowledge the valuable support of Mr. Andrej Miche1cich, Financial Officer of
ICTP, Ms. Manuela Vascotto and Alessandra Ricci for their continuous assistance and
wise counselling in financial matters. Our special thanks go to Ms. Dilys Grilli for her
generous preparation of part of the manuscript. Finally, we would like to thank Drs.
Willem Wamstaker and Jean-Pierre Lebreton for their collaboration in the selection of
the cover illustration.
JULIAN CHELA-FLORES, The Abdus Salam International Centre for Theoretical Physics, Italy and
Instituto de Estudios Avanzados (IDEA), Venezuela,
GUILLERMO A. LEMARCHAND, Instituto Argentino de Radioastronomia (CONICET), and
Centro de Estudios A vanzados, Universidad de Buenos Aires, Argentina
and
JUAN ORO, Department of Biochemical and Biophysical Sciences
University of Houston, Houston, TX 77204-5934, USA.
xii
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PREFACE
GROUP PHOTOGRAPH
CONTENTS
CONTENTS
A FEW WORDS OF WELCOME
General overview
Contemporary Radio Searches for Extraterrestrial Intelligence Frank Drake
SECTION 1. Introduction to Astrobiology
Origins: From the Big-Bang to Civilisation Julian Chela-Flores
Detectability of intelligent life in the universe: A search based in our knowledge of the laws of nature
Guillermo A. Lemarchand
Cosmos and cosmology Hector Rago
New developments in astronomy relevant to astrobiology Sabatino Sofia
SECTION 2. Chemical Evolution
Cosmochemical evolution and the origin of life on Earth John Oro
Chemical evolution in the early Earth Alicia Negron-Mendoza and Sergio Ramos-Bernal
Nitrogen fixation in planetary environments: A comparison between mildly reducing and neutral atmospheres
Rafael Navarro-Gonzalez
ix
xii
xv
xxi
xxiii
1
3
13
33
41
55
57
71
85
XVI
SECTION 3. Biological bases for the Study of the Evolution of Life in
the Universe
Darwinian dynamics and biogenesis Jesus Alberto Leon
Evolution of adaptive systems Hernan J Dopazo
Contemporary controversies within the framework of the revolutionary theory
Alicia Massarini
Molecular Biology and the reconstruction of microbial phylogenies: des liaisons dangereuses?
A. Becerra, E. Silva, L. Lloret, S. Islas, A.M. Velasco and A. Lazcano
SECTION 4. Study of Life in the Solar System
Astrobiology and the ESA Science Programme Willem Wamsteker and Augustin Chicarro
The chemical composition of comets Humberto Campins
SECTION 5. Origins of cognitive systems
Information, life and brains Juan G. Roederer
The origin of the neuron: The first neuron in the phylogenetic tree of life
Raimundo Villegas, Cecilia Castillo and Gloria M. Villegas
97
99
109
121
135
151
153
163
177
179
195
Origin of Synapses: A scientific account or the story of a hypothesis Emesto Palacios-Prii
Origins oflanguage: The evolution of human speech M.E. Medina-Callarotti
SECTION 6: Philosophical implications of the search for
extraterrestrial life
Astrophysics and Meta-Technics Ernesto Mayz Vallenilla
Deeper Questions: The search for darwinian evolution in our solar system
Julian Chela-Flores
SECTION 7: Round-table
Report on the round-table "Music of the spheres" Juan G. Roederer
SECTION 8: Contributions from participants
illtimate paradoxes of time travel Gustavo E. Romero and Diego F Torres
Do wormholes exist? Diego F Torres and Gustavo E. Romero
Heterogeneous radiolysis of succinic acid in the presence of sodiummontmorillonite. Implications to prebiotic chemistry
M Colin-Garcia, A. Negron-Mendoza and S. Ramos-Bernal
Condensed matter surfaces in prebiotic chemistry S. Ramos-Bernal and A. Negron-Mendoza
xvii
213
225
233
235
241
247
249
251
253
259
263
267
XVlll
Irradiation of adenine adsorbed in Na-Montmorillonite. Implications to chemical evolution studies
A. Guzman-Marmolejo, S. Ramos-Bernal end A. Negron-Mendoza
Accumulation of alkanes ~ n-C18 on the early Earth Vicente Marcano, Pedro Benitez and Ernesto Palacios-Prii
Advantages of the alkanes ~ n-C18 as protectors for the synthesis and survival of critical biomolecules in the early Earth
Vicente Marcano, Pedro Benitez and Ernesto Palacios-Prii
Evidence a of a nitrogen deficiency as a selective pressure towards the origin of biological nitrogen fixation in the early Earth
Leonel Calva-Alejo, Delphine Nna. Mvondo, Christopher McKay and R. Navarro-Gonzalez
RNA-binding peptides as early molecular fossils Luis Delaye and Antonio Lazcano
On the role of genome duplications in the evolution of prokaryotic chromosomes
S. Islas, A. Castillo, H. G. Vazquez and A. Lazcano
Experimental simulation of volcanic lightning on early Mars Antigona Segura and Rafael Navarro-Gonztilez
Tropical Alpine environments: A plausible analog for ancient and future life on Mars
Itzel Perez-Chavez, Rafael Navarro-Gonzalez, Christopher P. McKay and Luis Cruz Kuri
Planetary habitable zones on Earth and Mars biophysical limits of life in planetry environments
Abel Mendez
Quantitative study of the effects of various energy sources on a Titan's simulated atmosphere
Sandra l. Ramirez and Rafael Navarro-Gonzalez
271
275
279
283
285
289
293
297
303
307
Life extinctions and gravitational coIlapse of ONeMg electrondegenerate objects
Jordi Gutierrez
NAME INDEX
SUBJECT INDEX
PARTICIPANTS
XIX
311
315
319
329
A FEW WORDS OF WELCOME
JOHN ORO
Department of Biology and Biochemistry University of Houston Houston TX 77204-5934, USA
Good morning, distinguished Professor Dr. Ernesto Mayz Vallenilla, former president and founder of the Simon Bolivar University (USB), professor Freddy Malpica, current president of USB, distinguished academic authorities, ladies and gentlemen.
A most hearty welcome to all of you, authorities, sponsors, invited speakers, students and other persons that have come from all around the planet to attend and participate in the first IberoAmerican School of Astrobiology (IASA).
First of all I have to congratulate Professor Julian Chela-Flores from the Abdus Salam International Center for theoretical Physics, in Trieste, who has organized this magnificent educative congress called lAS A. This scientific meeting is the first School of Astrobiology and promises to be one of the best meetings in this field. The participants are well known scientists from a dozen Spanish speaking countries, including several from North-America and Europe. We have the privilege to have among us Dr. Frank Drake, president of the SET! Institute, pioneer in the search for extraterrestrial intelligent life, and we are looking forward to his usual active participation in the meeting.
I also need to congratulate all the students that attend this meeting, and specially all the institutions that have made possible this important School of Astrobiology, here in Caracas, and its excellent organization by the Institute of Advanced Studies (IDEA) from the University Simon Bolivar.
In addition to the Centro Internacional de Fisica Teorica and the Centro Internacional de Ingenieria Genetica y Biotecnologia from Trieste, Italy, the sponsor institutions of IASA are the following:
Oficina del rector( Universidad Simon Bolivar), NASA Headquarters, European Space Agency, TAL VEN Programme (Delegacion Permanente de Venezuela ante la UNESCO), The SET! Institute, Centro Latinoamericano de Fisica, The Third World Academy of Sciences, Academia de Ciencias Fisicas, Matematicas y Naturales, Red Latinoamericana de Biologfa, The Planetary Society, Oficina de Promoci6n y Mercadeo(IDEA Convention Center), The Latin American Academy of Sciences (Fondo ACAL), Alberto Vollmer Foundation, Escuela Emil Friedman, Fundaci6n J. Or6, Red Latinoamericana de Astronornia.
It has been said that astrobiology, bioastronomy and exobiology are "sciences" that lack their own subject of study, I mean, that it has not been demonstrated yet that extra-
XXI
XXll JOHN ORO
terrestrial life exists. Even though it can not be demonstrated mathematically like the relativity theory of Einstein, we can say like Dr. Paul Butler has recently said, echoing and extending the thoughts and statements of Plutarco and Giordano Bruno: "The Universe is too immense for us to be the only intelligent beings."
Briefly the ideas that will be presented in this School of Astrobiology include the following:
(1) Origins of the universe and cosmic evolution (2) Organic matter, interstellar clouds, comets and meteors (3) Origin of the solar system, meteorites, planetary atmospheres and catastrophic
impacts (4) Chemical evolution on Earth and Titan (5) Origin and evolution of life and intelligent life (6) Search for extraterrestrial civilizations (7) Evolutionary theory. From the cenancestor to eucariotes and beyond (8) The origin of neurons, the human brain and language (9) The Galileo mission (10) The possibility of life on Mars and Europe (11) "Mars Express" and beyond.
At the end we will have the honor that an astronaut from Johnson Space Center of Houston, Garrett Reisman will deliver a lecture about "The future of human missions in the exploration of the solar system"
Of course there are a lot of things that we ignore. We hope that from the questions of students or other participants we will clarify or refine our knowledge. So, please ask as many questions as you want to all the speakers. We believe that the dialogue we will excite us and we will contribute in making a better "School" of IASA. It is with meetings like this and future research that we may be able to solve the most fundamental question of mankind "Are we alone in the Universe?"
Thanks for your attention!
CONTEMPORARY RADIO SEARCHES FOR EXTRA TERRESTRIAL INTELLIG ENCE
FRANK DRAKE
SETI Institute Mountain View, California, 94043, USA
For forty years now, radio searches have been conducted in efforts to detect extraterrestrial intelligent radio signals. They exploit the abilities of radio telescopes, as explained beautifully by Guillermo Lemarchand at this School. Although the motivations and abilities of extraterrestrial technologies are not predictable, we nonetheless consider, as we have for forty years, that it is most promising to search for signals at radio wavelengths, and in particular the "microwave" wavelengths of the order of lO-cm.
Why is this? It is not because we are particularly adept at microwave technology, or that we expect the extraterrestrials to be focused on microwaves for communication. Rather, it is because the physics and arrangement of the universe favor microwaves for interstellar communication. The levels of cosmic noise at all relevant electromagnetic wavelengths are now very well known from observation. At frequencies below about 1 Ghz, there is intense cosmic radio noise due to radiation from relativistic electrons orbiting in the magnetic fields of the interstellar medium. At frequencies between about 1 Ghz and 20 Ghz, the primary source of noise is the relic radiation from the Big Bang. This creates a constant radio brightness temperature, all over the sky, of about 2.8 K over this portion of the spectrum. At higher frequencies, the quantum nature of radiation and the randomicity of arrival times of received photons introduce noise into the power level of any signal that is received. This can be represented as an equivalent brightness temperature which exceeds that of the relic radiation, and grows linearly with frequency since the energy per photon increases linearly with frequency. An alternate way of expressing this limitation, should a detector sensitive to individual photons be used (these do not exist on Earth at radio frequencies, but do exist for infrared and higher frequencies, of course) is that the minimum detectable signal, one photon, requires a minimum received energy which is proportional to frequency. Overall, then, there is a minimum in the noise of a well-designed detection system at microwave frequencies. The second law of thermodynamics states clearly that no technological device can circumvent this noise; thus it limits sensitivity no matter what the expertise of a civilization. Thus it is reasonable to expect that other civilizations will exploit these frequencies for communication channels in deep space, just as we do. Then it is most promising, but not inevitable, that a successful search will be carried out at the microwave frequencies.
Within the microwave band of low noise occur some fundamental lines of the R atom (1420 Mhz) and the OR radical (several lines, the strongest at 1665 and 1667 Mhz). Since these molecules join to make water, a clearly important and perhaps essential material of life, the frequency band containing these frequencies has been
xxiii
XXIV FRANK DRAKE
dubbed "the water hole" and is considered a prime frequency band for searches for extraterrestrial transmissions. To date, some 60 radio searches have been made since the first modern search, Project Ozma, of 1960. Almost all have been limited by instrumental limitations and choice to frequency bands in the water hole.
The basic SET! radio strategy has been to use radio telescopes of the greatest available collecting area with very sensitive multi-channel receivers. The larger the collecting area, the weaker the signal which can be detected. Indeed, the volume of space from which signals of a given intrinsic power can be detected is just proportional to the diameter of a circular antenna having the same collecting area as the actual collecting area. Multi-channel receivers are desirable because the channel used by the extraterrestrials is totally unknown. The more narrow the transmission, with a given radiated power, the easier it is to detect. This makes it wise to use very narrow channels, in turn demanding that many channels be examined at once if any substantial portion of the total search spectrum is to be covered in a search. We do know that there is a minimum bandwidth to any interstellar signal, a result of multipath propagation through the chaotic electron clouds of the Milky Way. This minimum bandwidth depends on the radio frequency and distance to the source. It is typically about 0.1 Hertz in the Water Hole for sources at a distance of a kiloparsec or so. In order to make progress, most searches make a compromise between minimum bandwidth in the receiving system and total spectral coverage. A typical search bandwidth is about 1 Hertz.
With bandwidths of the order of 1 Hertz, very many channels are called for to provide any substantial overall frequency coverage in a reasonable time. Until recently this was an insurmountable problem. However, the development of low cost computers, and, in particular, special "digital signal processing" computer chips have made possible the construction at affordable cost, perhaps $100,000, of receivers which may monitor as many as 100 million channels at once. This is a remarkable accomplishment, but creates a new challenge, which is to sort through the flood of data from such a system for evidence of intelligent signals. A typical system may be providing 100 million data points per second. To make the challenge even more difficult, the signals may exist in several channels simultaneously, may be pulsed periodically, as is typical of radar, and be drifting in frequency due to a changing Doppler effect or the design of the transmitter system. Other variations are possible. Again, this challenge can be and has been met through the application of special affordable computer systems and, particularly, special algorithms which search for a variety of signal types in the data. For example, the system of Project Phoenix, of the SET! Institute, can detect all the forms of signal just mentioned.
To add a still further challenge, and perhaps the most difficult one to deal with, is radio frequency interference, "RFI", from our own transmitters. All radio telescopes have some sensitivity in all directions; if there is a strong enough signal source visible to the telescope from any direction, the telescope will receive the signal, and it will be identified as an intelligent signal. Our civilization is a very prolific source of radio signals. In the entire developed world there are always present television signals which are detectable by the very sensitive SET! systems, even though the TV signal is so weak as to be 'unusable by a typical TV set. There may be tens of such signals detectable, even at remote sites. Aircraft provide large number of signals, both through their communication systems but also as a result of the sophisticated air traffic control systems now found throughout the world. There are many other sources of signals,
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such as cellular phones. Even at the most remote site, a host of strong signals are received from a huge number of transmitters on satellites. Most of these signals are in the Water Hole. The overall result is that every radio spectrum recorded by SETI systems contains many, perhaps fifty or more, human-created signals.
There is no simple so~ution to this RFI problem. One very simple but powerful step is to keep a catalog of detected signals; when the same signal is seen with the telescope looking in more than one place, it is an interfering signal. Some systems, such as the one at Harvard University, use two feed horns on the telescope, creating two beams. A true extraterrestrial signal will appear in first one beam and then the other, with a precise time delay. This can be used as a criterion to identify an extraterrestrial signal and reject RFI. Other projects, including the Harvard project and Project SERENDIP and its subsidiary, seti@home, observe the same point in the sky and same frequency at quite separate times. If the same signal appears twice or more, it is considered a prime candidate to be a true extraterrestrial signal, and follow-up observations are made.
In the case of Project Phoenix, a more definitive but expensive approach is used. A second telescope, perhaps hundreds or thousands of kilometers from the main search instrument, is fitted with a sensitive receiver and a minimal multi-channel receiver. Any detected signals at the main telescope are examined for a drift in frequency with time as is to be expected from changing Doppler effect, itself a result of the changing velocity component of the telescope along the line-of-site due to the rotation of the Earth. If the easily calculated expected frequency drift is detected, the information about the candidate signal is relayed to the second telescope, and it searches for the signal. If it is not seen, it means the signal was local RFI which mimicked a true signal. If the signal is seen, the second telescope should observe a different radio frequency and frequency drift, which can be precisely calculated. Because of its ,separation from the main telescope, the velocity component of the second telescope and its derivative will be different. This offers an immediate and conclusive test for the origin of the signal. It even works well with signals from distant spacecraft in the solar system, as has been demonstrated several times. Because of the power of this approach, Project Phoenix has identified the source of all signals it has ever detected. None have been of extraterrestrial intelligent origin.
Recent studies of the next desirable steps in radio SETI have recognized that the greatest weakness in current SETI programs has been the lack of on-going, nearly fulltime, access to very large radio telescopes. Project Phoenix, for example, uses the world's largest Arecibo telescope, but only twenty days a year are available to the project. This is very inefficient, and the inefficiency is enhanced by the need to move personnel frequently, restore equipment to proper working order after a long shut down, and to cope with changes in the telescope itself between observing periods. Other projects use only small telescopes, or have to cede control of the telescope pointing to other observers most of the time, in a compromise in which the SETI observers observe in a "parasitic" mode. A further concern is that true SETI signals may be transient, and success in the enterprise may require frequent, or almost constant, monitoring, of many places in the sky and many radio frequencies.
Both of these concerns call for the creation of very large radio telescopes dedicated to the SETI enterprise. Until recently, this was thought impossible because the large funding required, of the order of $100 million, seemed far beyond what might
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be available. Now there is hope in sight. The many discoveries supporting the idea that there are many habitable planets in the universe, and the improvement in SET! systems, have greatly increased interest in SET! by potential funding sources. Furthermore, the same improvement in computers and decreases in costs which facilitated the solutions to the multi-channel and RFI problems have made the construction of large telescope collecting areas possible at acceptable cost.
This has led to two major projects. The first is the "lhT", or One Hectare Telescope, of the SET! Institute. In this project a radio telescope with an energy collecting area of one hectare (10,000 square meters) will be constructed by utilizing a close-packed array of between 500 and 1000 small antennas, each three to five meters in size. These will be interconnected using fibre optics and digital time delays, all controlled by sophisticated computers, to produce the same effective collecting area as a single one hectare telescope. Not only will this reduce the price to something like $25 million, but also the system offers other important advantages. By using many time delays, it is possible to synthesize a large number of beams on the sky simultaneously, allowing SET! searches to proceed much more quickly, as long as the multi-channel receivers necessary for each beam are available. This capability also makes possible simultaneous SET! and conventional astronomy observations, allowing full-time use by both SET! scientists and those working on such objects as pulsars, quasars, etc. This project is now under development, and it is expected that the IhT will go into operation in about 2005. It may turn out to be a prototype for a much large instrument, the "One Square Kilometer Array" which is being advocated as the next big step in radio astronomy by radio astronomers worldwide.
The second project is to build a telescope which looks at all the visible sky on all the frequencies of the water hole at all times. The basic principle here is simple. One uses an array of an enormous number of nearly isotropic, therefore very small, antennas. The power collected by these antennas is added together with different time delays to create beams in all possible directions in the sky, with all the frequency information being retained. A huge number of broad-band spectrum analyzers then study the power captured by each of the multitude of synthesized beams. Although simple in principle, the actual system depends for success entirely on enormous computer power. The present estimates is that a computer system which can carry out about ten to the twentieth power calculations per second is required. This is presently beyond both our technical and financial capability. However, if the increases in computer power and decreases in cost follow their historical trends, that is, following "Moore's Law", the required capability at an affordable cost should be available in perhaps a decade. Because of this expected delay in feasibility, for now only preliminary studies are being carried out.
Because of the prospects for major advances, as represented by these new projects, there is a great deal of excitement in the SET! community.
