Try to read this. Fascinating. "The Earth’s troposphere contains diverse forms and frag- ments of life that can be dispersed laterally or upwards by eddies. Volcanic eruptions can carry material to alti- tudes above 25 km (Deshler et al., 1992; Lambert et al., 1993; McCormick and Weiga, 1992; Valero and Pilewskie, 1992), and warm ascending currents can raise spores up to 15 km (Gregory, 1973). Fungi (e.g. Circinella muscae, Peni- cillium notatum, Aspergillus niger, Papulaspora anomala ), and non-sporeforming bacteria (e.g. Micrococcus albus and Mycobacterium luteum ) were captured in the altitude range of 48–77 km, using meteorological rockets (Imshenetsky et al., 1976). More recently, balloon experiments, carried out with strenuous efforts to avoid terrestrial contamination, detected viable cells throughout the 20–41 km range (Narlikar et al., 2003), including bacteria, ( Pseudomonas stutzeri , Bacillus simplex and Staphylococcus pasteuri ) and the fungus, En- gyodontium album (Wainwright, 2003). It is not inconceiv- able that small seeds, e.g. orchid seeds bearing wing like structures, adapted to wind dispersal, could be carried by air currents into the upper atmosphere. To escape from a planet an object must exceed the escape speed ν esc = (2 Gm / R a ) 1 / 2 , where G is the universal constant of gravitation; m is the planet mass; and R is nominally the distance from the centre of the planet to the top of the at- mosphere (Jones, 2004). The escape speed from the Earth is 11.2 km s − 1 . For comparison, from the Moon it is 2.4 km s − 1 and from Mars and Venus it is 5.0 and 10.4 km s − 1 , respec- tively. Projection of material in excess of escape speed could result from the impacts of comets, meteorites, and asteroids (Melosh, 1988; Vickery and Melosh, 1987), either acting di- rectly on the site of impact or on particles already in the atmosphere. That planet to planet transfer via impact phenomena can occur is proven by the finding on Earth of SNC meteorites originating from Mars as well as meteorites whose source is the Moon (Warren, 1994). Under certain circumstances, the physical conditions in the ejecta following impact could be sufficiently mild for small amounts of micro-organisms to survive (Fajardo-Cavazos et al., 2005; Horneck et al., 2001b; Mileikowsky et al., 2000; Wallis and Wickramasinghe, 2004; Weiss et al., 2000b; Wells et al., 2003), and planet to planet transfer times could be less than 10 years for a small pro- portion of ejected material (Gladman, 1997; Gladman and Burns, 1996). However, for the Martian meteorites than have been found on Earth, their estimated times spent in space are in the range of 10 5 –10 7 years. Over the first 0.5 Gyr of the primitive Earth, the calculated arrival rate of ejecta from Mars was greater than 2,000 per year (Mileikowsky et al., 2000); 0.01% of the ejecta from Earth land on Mars within 10 6 years; and the number of ejecta from Earth arriving on Mars during the past 4 × 10 9 years is of the order of 10 9 (Mileikowsky et al., 2000). In this respect it is of interest that a modelling study (Davies, 2003) concluded that the prob- ability of biogenesis on Mars at some time earlier than 3.9 Gyr is about six times higher than on Earth." Source - cc10.aubg.bg/students/UND090/23302420.pdf
Posted on: Thu, 03 Oct 2013 16:08:42 +0000
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