Natural transfer of viable microbes in space - 1. From Mars to Earth and Earth to Mars

Citation
C. Mileikowsky et al., Natural transfer of viable microbes in space - 1. From Mars to Earth and Earth to Mars, ICARUS, 145(2), 2000, pp. 391-427
Citations number
60
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
ICARUS
ISSN journal
0019-1035 → ACNP
Volume
145
Issue
2
Year of publication
2000
Pages
391 - 427
Database
ISI
SICI code
0019-1035(200006)145:2<391:NTOVMI>2.0.ZU;2-3
Abstract
The possibility and probability of natural transfer of viable microbes from Mars to Earth and Earth to Mars traveling in meteoroids during the first 0 .5 Ga and the following 4 Ga are investigated, including: radiation protection against the galactic cosmic ray nuclei and the solar r ays; dose rates as a function of the meteorite's radial column mass (radius x density), combined with dose rates generated by natural radioactivity wi thin the meteorite; and survival curves for some bacterial species using NA SA's HZETRN transport code other factors affecting microbe survival: vacuum; central meteorite tempera tures at launch, orbiting, and arrival; pressure and acceleration at launch ; spontaneous DNA decay; metal ion migration mean sizes and numbers of unshocked meteorites ejected and percentage falli ng on Earth, using current semiempirical results viable flight times for the microbe species Bacillus subtilis and Deinococc us radiodurans R1 the approximate fraction of microbes (with properties like the two species studied) viably arriving on Earth out of those ejected from Mars during the period 4 Ga BP to the present time, and during the 700 Ma from 4.5 to 3.8 Ga. Similarly, from Earth to Mars. The conclusion is that if microbes existed or exist on Mars, viable transfe r to Earth is not only possible but also highly probable, due to microbes' impressive resistance to the dangers of space transfer and to the dense tra ffic of billions of martian meteorites which have fallen on Earth since the dawn of our planetary system. Earth-to-Mars transfer is also possible but at a much lower frequency. (C) 2000 Academic Press.