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Sökning: WFRF:(Melosh Jay)

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1.
  • Schulte, Peter, et al. (författare)
  • Cretaceous Extinctions: Evidence Overlooked Response
  • 2010
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 328:5981, s. 975-976
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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2.
  • Schulte, Peter, et al. (författare)
  • The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary
  • 2010
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 327:5970, s. 1214-1218
  • Tidskriftsartikel (refereegranskat)abstract
    • The Cretaceous-Paleogene boundary similar to 65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroid impact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. Notably, a single ejecta-rich deposit compositionally linked to the Chicxulub impact is globally distributed at the Cretaceous-Paleogene boundary. The temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling) lead us to conclude that the Chicxulub impact triggered the mass extinction.
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3.
  • Valtonen, Mauri, et al. (författare)
  • NATURAL TRANSFER OF VIABLE MICROBES IN SPACE FROM PLANETS IN EXTRA-SOLAR SYSTEMS TO A PLANET IN OUR SOLAR SYSTEM AND VICE VERSA
  • 2009
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 690:1, s. 210-215
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate whether it is possible that viable microbes could have been transported to the Earth from planets in extra-solar systems by means of natural vehicles such as ejecta expelled by comets or asteroid impacts on such planets. The probabilities of close encounters with other solar systems are taken into account as well as the limitations of bacterial survival times inside ejecta in space, caused by radiation and DNA decay. The conclusion is that no potentially DNA/RNA life-carrying ejecta from another solar system in the general Galactic star field landed on the Earth before life already existed on the Earth, even if the microbial survival time in space is as long as tens of millions of years. However, if the Sun formed initially as a part of a star cluster, as is commonly assumed, we cannot rule out the possibility of transfer of life from one of the sister systems to us. Likewise, there is a possibility that some extra-solar planets carry life that originated in our solar system. It will be of great interest to identify the members of the Sun's birth cluster of stars and study them for evidence of planets and life on the planets. The former step may be accomplished by the GAIA mission, the latter step by the SIM and DARWIN missions. Therefore it may not be too long until we have experimental knowledge to answer the question of whether the natural transfer of life from one solar system to another has actually taken place.
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