Abstract：
:In spite of the spectacular developments in our understanding of the molecular basis that underlies biological phenomena, we still lack a generally agreed-upon definition of life, but this is not for want of trying. Life is an empirical concept; and, as suggested by the many unsuccessful efforts to define it, this task is likely to remain, at best, a work in progress. Although phenomenological characterizations of life are feasible, a precise definition of life remains an elusive intellectual endeavor. This is not surprising: as Nietszche once wrote, there are concepts that can be defined, whereas others only have a history. The purpose of this essay is to discuss some of the manifold (and often unsatisfactory) definitions of life that have been attempted from different intellectual and scientific perspectives and reflect, at least in part, the key role that historical frameworks play. Although some efforts have been more fruitful, the lack of an all-embracing, generally agreed-upon definition of life sometimes gives the impression that what is meant by life's origin is defined in somewhat imprecise terms and that several entirely different questions are often confused. The many attempts made to reduce the nature of living systems to a single living compound imply that life can be so well defined that the exact point at which it started can be established with the sudden appearance of the first replicating molecule. On the other hand, if the emergence of life is seen as the stepwise (but not necessarily slow) evolutionary transition between the non-living and the living, then it may be meaningless to draw a strict line between them.
journal_name
Astrobiologyjournal_title
Astrobiologyauthors
Tirard S,Morange M,Lazcano Adoi
10.1089/ast.2010.0535subject
Has Abstractpub_date
2010-12-01 00:00:00pages
1003-9issue
10eissn
1531-1074issn
1557-8070journal_volume
10pub_type
历史文章,杂志文章相关文献
ASTROBIOLOGY文献大全abstract：:Terrestrial moons with masses >0.1 M (symbol in text) possibly exist around extrasolar giant planets, and here we consider the energetics of how they might form. Binary-exchange capture can occur if a binary-terrestrial object (BTO) is tidally disrupted during a close encounter with a giant planet and one of the binar...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2012.0892
更新日期：2013-04-01 00:00:00
abstract：:Dryness is one of the main environmental challenges to microbial survival. Understanding the threshold of microbial tolerance to extreme dryness is relevant to better constrain the environmental limits of life on Earth and critically evaluate long-term habitability models of Mars. Biomolecular proxies for microbial ad...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2017.1705
更新日期：2018-07-01 00:00:00
abstract：:The NASA Astrobiology Roadmap provides guidance for research and technology development across the NASA enterprises that encompass the space, Earth, and biological sciences. The ongoing development of astrobiology roadmaps embodies the contributions of diverse scientists and technologists from government, universities...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/153110703769016299
更新日期：2003-07-01 00:00:00
abstract：:In June 2003, the geochemical composition of geothermal fluids was determined at 9 sites in the Vulcano hydrothermal system, including sediment seeps, geothermal wells, and submarine vents. Compositional data were combined with standard state reaction properties to determine the overall Gibbs free energy (DeltaG(r) ) ...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2007.0128
更新日期：2007-12-01 00:00:00
abstract：:We have observed filamentous carbon-rich structures in samples drilled at 3 different seamounts that belong to the Emperor Seamounts in the Pacific Ocean: Detroit (81 Ma), Nintoku (56 Ma), and Koko Seamounts (48 Ma). The samples consist of low-temperature altered basalts recovered from all 3 seamounts. The maximum dep...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2007.0226
更新日期：2008-12-01 00:00:00
abstract：:Formation of microtubules in volcanic glass from subsurface environments has been widely attributed to in situ activity of micro-organisms, but evidence directly linking those structures to biological processes remains lacking. Investigations into the alternative possibility of abiotic tubule formation have been limit...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2017.1811
更新日期：2019-01-01 00:00:00
abstract：:As photosynthesis on Earth produces the primary signatures of life that can be detected astronomically at the global scale, a strong focus of the search for extrasolar life will be photosynthesis, particularly photosynthesis that has evolved with a different parent star. We take previously simulated planetary atmosphe...
journal_title：Astrobiology
pub_type： 杂志文章,评审
doi：10.1089/ast.2006.0108
更新日期：2007-02-01 00:00:00
abstract：:During three low-altitude (99, 66, 66 km) flybys through the Enceladus plume in 2010 and 2011, Cassini's ion neutral mass spectrometer (INMS) made its first high spatial resolution measurements of the plume's gas density and distribution, detecting in situ the individual gas jets within the broad plume. Since those fl...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2017.1647
更新日期：2017-09-01 00:00:00
abstract：:We investigate a new mechanism for producing oxidants, especially hydrogen peroxide (H2O2), on Mars. Large-scale electrostatic fields generated by charged sand and dust in the martian dust devils and storms, as well as during normal saltation, can induce chemical changes near and above the surface of Mars. The most dr...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2006.6.439
更新日期：2006-06-01 00:00:00
abstract：:Stromatolite structures in Early Archean carbonate deposits form an important clue for the existence of life in the earliest part of Earth's history. Since Mars is thought to have had similar environmental conditions early in its history, the question arises as to whether such stromatolite structures also evolved ther...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2009.0388
更新日期：2010-04-01 00:00:00
abstract：:The bicarbonate-buffered anoxic vent waters at Chocolate Pots hot springs in Yellowstone National Park are 51-54°C, pH 5.5-6.0, and are very high in dissolved Fe(II) at 5.8-5.9 mg/L. The aqueous Fe(II) is oxidized by a combination of biotic and abiotic mechanisms and precipitated as primary siliceous nanophase iron ox...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2013.1122
更新日期：2014-06-01 00:00:00
abstract：:Rover missions to the rocky bodies of the Solar System and especially to Mars require lightweight, portable instruments that use minimal power, require no sample preparation, and provide suitably diagnostic mineralogical information to an Earth-based exploration team. Short-wave infrared (SWIR) spectroscopic instrumen...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2004.4.359
更新日期：2004-10-01 00:00:00
abstract：:Meaningful motion is an unambiguous biosignature, but because life in the Solar System is most likely to be microbial, the question is whether such motion may be detected effectively on the micrometer scale. Recent results on microbial motility in various Earth environments have provided insight into the physics and b...
journal_title：Astrobiology
pub_type： 杂志文章,评审
doi：10.1089/ast.2015.1376
更新日期：2016-10-01 00:00:00
abstract：:Evaporation of silica-rich geothermal waters is one of the main abiotic drivers of the formation of silica sinters around hot springs. An important role in sinter structural development is also played by the indigenous microbial communities, which are fossilized and eventually encased in the silica matrix. The combina...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2012.0887
更新日期：2013-02-01 00:00:00
abstract：:There is concern in many developed countries that school students are turning away from science. However, students may be choosing not to study science and dismissing the possibility of a scientific career because, in the junior secondary years, they gain a false view of science and the work of scientists. There is a ...
journal_title：Astrobiology
pub_type： 杂志文章,评审
doi：10.1089/ast.2012.0873
更新日期：2012-12-01 00:00:00
abstract：:We propose a terahertz (far-infrared) circular dichroism-based life-detection technology that may provide a universal and unequivocal spectroscopic signature of living systems regardless of their genesis. We argue that, irrespective of the specifics of their chemistry, all life forms will employ well-structured, chira...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/153110703322610609
更新日期：2003-10-01 00:00:00
abstract：:The astrobiological significance of certain environment types on Mars strongly depends on the temperature, duration, and chemistry of liquid water that was present there in the past. Recent works have focused on the identification of signs of ancient water on Mars, as it is more difficult to estimate the above-mention...
journal_title：Astrobiology
pub_type： 杂志文章,评审
doi：10.1089/ast.2011.0686
更新日期：2012-06-01 00:00:00
abstract：:The possible meteorite parent body origin of Earth's pregenetic nucleobases is substantiated by the guanine (G), adenine (A), and uracil (U) measured in various meteorites. Cytosine (C) and thymine (T), however, are absent in meteorites, making the emergence of an RNA and later RNA/DNA/protein world problematic. We in...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2015.1451
更新日期：2016-11-01 00:00:00
abstract：:Abstract Technologies that enable rapid and efficient extraction of biomarker compounds from various solid matrices are a critical requirement for the successful implementation of in situ chemical analysis of the martian regolith. Here, we describe a portable subcritical water extractor that mimics multiple organic so...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2007.0154
更新日期：2008-06-01 00:00:00
abstract：:Photosynthesis on Earth can occur in a diversity of organisms in the photosynthetically active radiation (PAR) range of 10 nmol of photons m(-2) s(-1) to 8 mmol of photons m(-2) s(-1). Similar considerations would probably apply to photosynthetic organisms on Earth-like planets (ELPs) in the continuously habitable zon...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2006.6.668
更新日期：2006-08-01 00:00:00
abstract：:Recent measurements of methane (CH4) by the Mars Science Laboratory (MSL) now confront us with robust data that demand interpretation. Thus far, the MSL data have revealed a baseline level of CH4 (∼0.4 parts per billion by volume [ppbv]), with seasonal variations, as well as greatly enhanced spikes of CH4 with peak ab...
journal_title：Astrobiology
pub_type： 杂志文章,评审
doi：10.1089/ast.2018.1917
更新日期：2018-10-01 00:00:00
abstract：:The discovery by NASA's Cassini mission at Saturn in 2005 of a large plume of material erupting from the south polar terrain of Enceladus, sourced within a subsurface ocean of salty liquid water laced with organic compounds, has brought together scientists from a diverse range of disciplines over the last decade to ev...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2017.1711
更新日期：2017-09-01 00:00:00
abstract：:Organics are expected to exist on Mars based on meteorite infall, in situ production, and any possible biological sources. Yet they have not been detected on the martian surface; are they there, or are we not capable enough to detect them? The Viking gas chromatograph-mass spectrometer did not detect organics in the h...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2010.0498
更新日期：2010-07-01 00:00:00
abstract：:Nitrogen is the major component of Earth's atmosphere and plays important roles in biochemistry. Biological systems have evolved a variety of mechanisms for fixing and recycling environmental nitrogen sources, which links them tightly with terrestrial nitrogen reservoirs. However, prior to the emergence of biology, al...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2017.1700
更新日期：2018-07-01 00:00:00
abstract：:The emergence of chirality in enantioselective autocatalysis for compounds unable to transform according to the Frank-like reaction network is discussed with respect to the controversial limited enantioselectivity (LES) model composed of coupled enantioselective and non-enantioselective autocatalyses. The LES model ca...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2012.0904
更新日期：2013-02-01 00:00:00
abstract：:This experiment was aimed at establishing, for the first time, the survival capability of lichens exposed to space conditions. In particular, the damaging effect of various wavelengths of extraterrestrial solar UV radiation was studied. The lichens used were the bipolar species Rhizocarpon geographicum and Xanthoria e...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2006.0046
更新日期：2007-06-01 00:00:00
abstract：:The Mars Organic Analyzer (MOA) has enabled the sensitive detection of amino acid and amine biomarkers in laboratory standards and in a variety of field sample tests. However, the MOA is challenged when samples are extremely acidic and saline or contain polyvalent cations. Here, we have optimized the MOA analysis, sam...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2009.0357
更新日期：2009-11-01 00:00:00
abstract：:The emergence of an RNA entity capable of synthesizing peptides was a key prebiotic development. It is hypothesized that a precursor of the modern ribosomal exit tunnel was associated with this RNA entity (e.g., "protoribosome" or "bonding entity") from the earliest time and played an essential role. Various compounds...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2011.0692
更新日期：2012-01-01 00:00:00
abstract：:Over the next two decades, NASA and ESA are planning a series of space-based observatories to find Earth-like planets and determine whether life exists on these planets. Previous studies have assessed the likelihood of detecting life through signs of biogenic gases in the atmosphere or a red edge. Biogenic gases and t...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2010.0495
更新日期：2010-11-01 00:00:00
abstract：:The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole-disk Earth model simulatio...
journal_title：Astrobiology
pub_type： 杂志文章
doi：10.1089/ast.2011.0642
更新日期：2011-06-01 00:00:00
