دانلود کتاب Handbook of astrobiology

Astrobiology is defined as the study of the origin, evolution,
distribution, and future of life in the universe (NASA’s definition;
Des Marais et al. 2008). Astrobiology seeks to answer
fundamental questions about the beginning and evolution of
life on Earth, possible existence of extraterrestrial life, and
the future of life on Earth and beyond. Astrobiology scope is
delineated in the NASA’s astrobiology roadmap (Des Marais
et al. 2008). Specific goals include understanding the emergence
of life on Earth, determining how the early life on
Earth interacted and evolved with its changing environment,
understanding the evolutionary mechanisms and environmental
limits of life, exploring habitable environments in our solar
system and searching for life, understanding the nature and
distribution of habitable environments in the universe, and
recognizing signatures of life on the early Earth and on other
worlds. The NASA’s astrobiology map is being updated as
the astrobiology field advances. A similar roadmap has been
developed for astrobiology research in Europe (Horneck et al.
2015, 2016). The topic of these roadmaps is further discussed
and updated in Section 1 of this handbook.
Astrobiology is a young science that acquired its name
only in 1995 (named by Wes Huntress from NASA; Catling
2013). Astrobiology evolved from its predecessor, exobiology,
which is the study of the origin of life and of possible
life outside Earth (Dick and Strick 2004; Dick 2007). The
term exobiology was coined in 1960 (by Joshua Lederberg).

The difference between the two fields is that astrobiology is
broader and notably includes the evolution of life on Earth.
The exobiology era coincided with the space missions, notably
the Viking mission on Mars in 1976, which followed a
series of reconnaissance missions in the 1960s and early
1970s. The Viking mission searched for the microbial life on
Mars (DiGregorio 1997; Jones 2004), but it did not confirm
its existence. The early experiments that used radio astronomy
to search for extraterrestrial intelligence by the Search
for Extraterrestrial Intelligence (SETI) program (Tarter 2007)
did not result in positive findings. In 1996, the analysis of the
Martian meteorite ALH84001, which was found in Antarctica,
indicated possible presence of the fossils of bacterial life
(Goldsmith 1997; Jones 2004), but the results were not convincing
enough. Disappointments regarding a lack of positive
results in the search for extraterrestrial life (Dick and Strick
2004; Dick 2007, 2012) continue to this date. The only life we
know of is the life on Earth. Search for extraterrestrial life and
extraterrestrial intelligence is further discussed in Sections 10
through 12 of this handbook.

While astrobiology is a new science, it comes from
a very old and long history of ideas, which go all the way
back to the antiquity. The history of one of the core ideas
of astrobiology, a possibility of extraterrestrial life, is
described in the books: “Plurality of worlds: The origins
of the extraterrestrial life debate from Democritus to Kant”
(Dick 1984), “The extraterrestrial life debate, 1750–1900”
(Crowe 1999), “Medieval cosmology: Theories of infinity,
place, time, void, and the plurality of worlds” (Duhem 1987),
and other sources. A comprehensive coverage of the ideas
about extraterrestrial intelligent life is covered in the books:
“Extraterrestrials: Science and alien intelligence” (Regis
1987), “Extraterrestrials: Where are they?” (Zuckerman
and Hart 1995), “Beyond contact: A guide to SETI and
communicating with alien civilizations” (McConnell 2001),
and “Civilizations beyond Earth: Extraterrestrial life and
society” (Vakoch and Harrison 2013), among other sources.
The future of life on Earth and its potential uniqueness are
discussed in the books “The life and death of planet Earth:
How the new science of astrobiology charts the ultimate fate
of our world” (Ward and Brownlee 2002), and “Rare Earth:
Why complex life is uncommon in the universe” (Ward and
Brownlee 2004). Search for exoplanets, some of which may
be habitable, is a subject of recent studies (Kasting 2010;
Summers and Trefil 2017). This subject is further covered in
Section 12 of this handbook.

The major hypothesis about the origin of life on Earth,
which later became accepted as a key foundation of both exobiology
and astrobiology, was proposed independently by A.I.
Oparin in 1924 and J. B. S. Haldane in 1929 (Oparin 1965,
1968, 1994; Deamer and Fleischaker 1994; Haldane 1994).
This hypothesis states that the origin of life on Earth can be
understood based only on the laws of chemistry and physics.
Life arose in Earth’s distant past by chemical reactions and
physical processes under the specific conditions on the early
Earth and over a long period of time. Numerous rapid developments
based on the Oparin–Haldane proposal followed
(Miller and Orgel 1974; Mason 1991; Brack 2000; Zubay
2000; Chela-Flores 2001, 2011; Fenchel 2002; Lurquin 2003;
Gilmour and Sephton 2004; Luisi 2006; Sullivan and Baross
2007; Sullivan and Carney 2007; Kolb 2014a; Longstaff
2015). New developments on chemical origins of life and
prebiotic chemistry are covered in Section 5 of this handbook.