Abstract:
:Over the past few years a series of searches for interstellar radio beacons have taken place using the Parkes radio telescope. Here we report hitherto unpublished results from a search for optical beacons from 60 solar-type stars using the Perth-Lowell telescope. We discuss the significance of the null results from these searches, all of which were based on the interstellar contact channel hypothesis. While the null results of all searches to date can be explained simply by the nonexistence of electromagnetically communicating life elsewhere in the Milky Way, four other possible explanations that do not preclude its existence are proposed: (1) Extraterrestrial civilizations desiring to make contact through the use of electromagnetic beacons have a very low density in the Milky Way. (2) The interstellar contact channel hypothesis is incorrect, and beacons exist at frequencies that have not yet been searched. (3) The search has been incomplete in terms of sensitivity and/or target directions: Beacons exist, but more sensitive equipment and/or more searching is needed to achieve success. (4) The search has occurred before beacon signals can be expected to have arrived at the Earth, and beacon signals may be expected in the future. Based on consideration of the technology required for extraterrestrial civilizations to identify target planets, we argue that the fourth possibility is likely to be valid and that powerful, easily detectable beacons could be received in coming centuries.
journal_name
Astrobiologyjournal_title
Astrobiologyauthors
Blair DG,Zadnik MGdoi
10.1089/153110702762027880keywords:
subject
Has Abstractpub_date
2002-10-01 00:00:00pages
305-12issue
3eissn
1531-1074issn
1557-8070journal_volume
2pub_type
杂志文章相关文献
ASTROBIOLOGY文献大全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::The Atacama Desert has long been considered a good Mars analogue for testing instrumentation for planetary exploration, but very few data (if any) have been reported about the geomicrobiology of its salt-rich subsurface. We performed a Mars analogue drilling campaign next to the Salar Grande (Atacama, Chile) in July 2...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2011.0654
更新日期:2011-12-01 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:UNLABELLED:Fluid inclusions trapped in ancient halite can contain a community of halophilic prokaryotes and eukaryotes that inhabited the surface brines from which the halite formed. Long-term survival of bacteria and archaea and preservation of DNA have been reported from halite, but little is known about the distribu...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2015.1397
更新日期:2016-06-01 00:00:00
abstract::The Dry Valleys of Antarctica are one of the coldest and driest environments on Earth with paleosols in selected areas that date to the emplacement of tills by warm-based ice during the Early Miocene. Cited as an analogue to the martian surface, the ability of the Antarctic environment to support microbial life-forms ...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2010.0583
更新日期:2011-05-01 00:00:00
abstract::Knowledge and understanding of the martian environment has advanced greatly over the past two decades, beginning with NASA's return to the surface of Mars with the Pathfinder mission and its rover Sojourner in 1997 and continuing today with data being returned by the Curiosity rover. Reduced carbon, however, is yet to...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2014.1220
更新日期:2015-06-01 00:00:00
abstract::Properties of avenues of transformation and their mutualism with forms of organization in dynamic systems are essential for understanding the evolution of prebiotic order. We have analyzed competition between two avenues of transformation in an A↔B system, using the simulation approach called BiADA (Biotic Abstract Du...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2012.0933
更新日期:2013-05-01 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::Two terrestrial environments that have been proposed as analogs for the iron oxide precipitation in the Meridiani Planum region of Mars include the Rio Tinto precipitates and southern Utah marble concretions. Samples of two typical Utah iron oxide concretions and iron oxide precipitates in contact with biofilms from R...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2006.6.527
更新日期:2006-08-01 00:00:00
abstract::We highlight the role of COSPAR and the scientific community in defining and updating the framework of planetary protection. Specifically, we focus on Mars "Special Regions," areas where strict planetary protection measures have to be applied before a spacecraft can explore them, given the existence of environmental c...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2016.1472
更新日期:2016-02-01 00:00:00
abstract::Recent discoveries about Europa--the probable existence of a sizeable ocean below its ice crust; the detection of hydrated sodium carbonates, among other salts; and the calculation of a net loss of sodium from the subsurface--suggest the existence of an alkaline ocean. Alkaline oceans (nicknamed "soda oceans" in analo...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/153110702753621394
更新日期:2002-04-01 00:00:00
abstract:UNLABELLED:We developed a prototype instrument called the Standoff Biofinder, which can quickly locate biological material in a 500 cm(2) area from a 2 m standoff distance with a detection time of 0.1 s. All biogenic materials give strong fluorescence signals when excited with UV and visible lasers. In addition, the lu...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2015.1400
更新日期:2016-09-01 00:00:00
abstract::The thermal springs Trollosen and Fisosen, located on the High Arctic archipelago Svalbard, discharge saline groundwaters rich in hydrogen sulfide and ammonium through a thick layer of permafrost. Large amounts of biomass that consist of filamentous microorganisms containing sulfur granules, as analyzed with energy di...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2010.0551
更新日期:2011-09-01 00:00:00
abstract::The primary objective of NASA's Mars Science Laboratory (MSL) mission, which will launch in 2011, is to characterize the habitability of a site on Mars through detailed analyses of the composition and geological context of surface materials. Within the framework of established mission goals, we have evaluated the valu...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2010.0491
更新日期:2010-09-01 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::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::A phylogenomic dating approach was used to identify potential age constraints for multiple archaeal groups, many of which have no fossil, isotopic, or biomarker record. First, well-resolved phylogenetic trees were inferred with the use of multiple gene sequences obtained from whole genome sequences. Next, the ability ...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2008.0247
更新日期:2009-03-01 00:00:00
abstract::Laser-Raman imagery is a non-intrusive, non-destructive analytical technique, recently introduced to Precambrian paleobiology, that can be used to demonstrate a one-to-one spatial correlation between the optically discernible morphology and kerogenous composition of permineralized fossil microorganisms. Made possible ...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2005.5.333
更新日期:2005-06-01 00:00:00
abstract::Water is the fundamental molecule for life on Earth. Thus, the search for hibernating life-forms in waterless environments is an important research topic for astrobiology. To date, however, the organizational patterns containing microbial life in extremely dry places, such as the deserts of Earth, the Dry Valleys of A...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2014.1162
更新日期:2014-07-01 00:00:00
abstract::Materials blasted into space from the surface of early Earth may preserve a unique record of our planet's early surface environment. Armstrong et al. (2002) pointed out that such materials, in the form of terrestrial meteorites, may exist on the Moon and be of considerable astrobiological interest if biomarkers from e...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2007.0215
更新日期:2008-04-01 00:00:00
abstract::Astrobiology is an inherently interdisciplinary area of study, demanding communication across multiple fields: astronomy, geochemistry, planetary science, and so on. Successful communication requires that researchers be aware of the basic findings, open questions, and tools and techniques of allied fields and possess ...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2017.1710
更新日期:2018-03-01 00:00:00
abstract::Understanding microbial diversity in spacecraft assembly clean rooms is of major interest with respect to planetary protection considerations. A coordinated screening of different clean rooms in Europe and South America by three German institutes [Deutsches Zentrum für Luft- und Raumfahrt (DLR), Leibniz-Institut DSMZ-...
journal_title:Astrobiology
pub_type: 杂志文章,评审
doi:10.1089/ast.2013.1024
更新日期:2013-12-01 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::Ultraviolet (UV) irradiation on the surface of Mars is an important factor that affects the survivability of microorganisms on Mars. The possibility of martian brines made from Fe2(SO4)3, MnSO4, and MgSO4 salts providing a habitable niche on Mars via attenuation of UV radiation was investigated on the bacteria Bacillu...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2020.2285
更新日期:2020-11-25 00:00:00
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::Life-detection instruments on future Mars missions may use surfactant solutions to extract organic matter from samples of martian rocks. The thermal and radiation environments of space and Mars are capable of degrading these solutions, thereby reducing their ability to dissolve organic species. Successful extraction a...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2013.1105
更新日期:2014-09-01 00:00:00
abstract::Equilibrium adsorption isotherm data for the purine base adenine has been obtained on several prebiotically relevant minerals by frontal analysis using water as a mobile phase. Adenine is far displaced toward adsorption on pyrite (FeS2), quartz (SiO2), and pyrrhotite (FeS), but somewhat less for magnetite (Fe3O4) and ...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/153110701753593874
更新日期:2001-01-01 00:00:00
abstract::Aqueous solutions on Mars are theorized to contain very different ion compositions than those on Earth. To determine the effect of such solutions on typical environmental micro-organisms, which could be released from robotic spacecraft or human exploration activity, we investigated the resistance of Sphingomonas desic...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2018.1840
更新日期:2019-01-01 00:00:00
abstract::Early Earth may have hosted a biologically mediated global organic haze during the Archean eon (3.8-2.5 billion years ago). This haze would have significantly impacted multiple aspects of our planet, including its potential for habitability and its spectral appearance. Here, we model worlds with Archean-like levels of...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2017.1666
更新日期:2018-03-01 00:00:00
abstract::Modern ecological niches are teeming with an astonishing diversity of microbial life in biofilms closely associated with mineral surfaces, which highlights the remarkable success of microorganisms in conquering the challenges and capitalizing on the benefits presented by the mineral-water interface. Biofilm formation ...
journal_title:Astrobiology
pub_type: 杂志文章
doi:10.1089/ast.2011.0776
更新日期:2012-08-01 00:00:00