Murata, N., Yamada, M., Nishida, I., Okuyama, H., Sekiya, J. and Hajime, W. (eds). Advanced research on plant lipids

Temporal variation of the zodiacal dust cloud

“…It has been assumed herein that the mass influx of comets to the inner planetary system is random. However, periodic modulation of the comet flux may arise through regular disturbances of the Oort cloud, whether by Galactic tides (Napier 1987;Matese et al 1995;, or even ± less probably ± by an unseen binary companion (Davis, Hut & Muller 1984). Waves of extinction through dust and impacts may then result (Napier 1998).…”

“…However, periodic modulation of the comet flux may arise through regular disturbances of the Oort cloud, whether by Galactic tides (Napier 1987;Matese et al 1995;, or even ± less probably ± by an unseen binary companion (Davis, Hut & Muller 1984). Waves of extinction through dust and impacts may then result (Napier 1998). Galactic perturbations of the Oort cloud yield flux amplitudes of order 2 to 5, and so estimates of the current impact hazard derived from the long-term lunar cratering record (Chapman & Morrison 1994) have to be treated with caution.…”

Impact cratering and the Oort Cloud

“…We find that order of magnitude increases in the impact rate of comets on to the Earth occur during encounters with molecular clouds of ≳5 × 10 4 M ⊙ and that such encounters take place quite frequently on geological time‐scales (Napier 2007). If, within a giant molecular cloud, there are at least 1.1 exosystems with a receptive planet and an impact environment permitting the escape of microbiota, life may propagate throughout the habitable zone of the Galaxy within the lifetime of the Galactic disc (Napier 2007). In addition to these sporadic episodes, periodic impact surges are also expected to occur due to the variable stress exerted on the Oort Cloud by the vertical Galactic tide.…”

“…It has been proposed that disturbances of the Oort Cloud due to encounters with spiral arms and molecular clouds would lead to episodes of bombardment of comets on to the Earth, and that these episodes would cause geological disturbances and mass extinctions of life such as the Cretaceous–Tertiary event of 65 Myr BP (Napier & Clube 1979). More recently, it has been pointed out that such episodes may also provide a mechanism for interstellar panspermia (Napier 2004, 2007; Wickramasinghe 2007). Microorganisms thrown from the surface of the Earth by large impacts may be ejected by radiation pressure into star‐forming regions within the passing nebula, and so seed protoplanetary nebulae within them.…”

Homochirality of Organic Matter – Objective Law or Curious Incident?

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Theo rigin of life on Earth presents one of the hottest problems of modern natural science.T hough the hypothesis of insemination of Earth with some kind of living matter from the cosmic environment still remains under discussion, [1,2] ideas of the emergence of life immediately on Earth attract much more attention. However,p athways of chemical evolutiono fo rganic and inorganic matter, first into primitive self-reproducing organic systems,and then into livingorganisms,still remain to be understood.M ost surprising is the fact that life on Earth emerged very soon after the formationo fo ur Solar System (about 4.6 billion years ago) -a lreadys ome hundred million years after the differentiation of melted matter and the formation of Earthss urface crust.

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