Titlebook: How Likely is Extraterrestrial Life?; J. Woods Halley Book 2012 The Author(s) 2012 Chemical evolution of life.Drake‘s equation discussed.E

考古學(xué)

fluffy

Biological Factors identify the presence of life. Attempts to identify the essential features required to label a material system as ‘a(chǎn)live’ are numerous, and necessarily arbitrary because the word ‘life’ can be defined by its user in many ways.

Nucleate

ingrate

Planetary Considerationseratures and feature huge gravitational fields at their surfaces. Some of moons of Jupiter and Saturn are regarded as having some possibility of harboring life, though none has been found to date and they are all at least as inhospitable as Mars.

下邊深陷

Direct Searches for Primitive Forms of Lifebout . years or more using present technology. (NASA does contemplate long term development of an interstellar probe). Here we briefly discuss results from such studies of Mars, Europa, a moon of Jupiter and Titan, a moon of Saturn. These are the objects of greatest current interest in the astrobiological efforts of NASA

Adjourn

superfluous

Astrophysical Factorsome dispute. However, there is strong evidence that, roughly one second after the expansion began, the initial material cooled sufficiently to leave mainly electromagnetic radiation, two kinds helium nuclear isotopes, two kinds of hydrogen nuclei (protons and deuterons) and electrons.

有機體

Unidentified Flying Objectsalmost universally acknowledges this. The so-called ‘Fermi Paradox’ arises because some of the estimates from the Drake equation discussed in Part I predict large number of biospheres and civilizations, whereas none have been observed.

exostosis

2191-9100 ewed in undergraduate and freshmen courses over many years PWhat does existing scientific knowledge about physics, chemistry, meteorology and biology tell us about the likelihood of extraterrestrial life and civilizations? And what does the fact that there is currently no credible scientific evidenc

Anthrp

Book 2012are still choosing a specialty. The difficulties and the range of possible answers to the title question are carefully addressed in the light of present understanding. The resulting perspective is distinctly different from those suggested by most other books on this topic.