1). Then the rough estimation is N impact = f 1 f 2 f 3 (R/r) 3 (1 AU)2/(4πs 2) 102. If we take the mean velocity of meteorites in the interstellar space as 10 (km/s), the elapsed time to travel 20 lyr is several Myr. Even though there are many uncertain factors, the probability of rocks originate from Earth to reach nearby star system is not so small. If the micro-organisms within the size (<1 cm) of meteorites are still viable for several Myr, we should investigate the panspermia learn more theories much further. Hildebrand, A et al. (1991). Chicxulub Crater; a possible Cretaceous/Tertiary boundary impact crater on the Yucatan Peninsula, Mexico.

Geology, 19: 867–871. Melosh, H. (2003). Exchange of Meteorites (and Life?) Between Silmitasertib supplier Stellar Systems. Astrobiology, 3:207. Udry, S. et al. (2007). The HARPS search for southern extra-solar planets. (astro-ph/0704.3841) Wallis, M. and Wickramasinghe, N (2004). Interstellar transfer of planetary find more microbiota. MNRAS. 348:52. E-mail: hara@cc.​kyoto-su.​ac.​jp Lithopanspermia Revisited: Origin of Life on Ceres? Joop M. Houtkooper Institute for Psychobiology and Behavioral Medicine, Justus-Liebig-Univerity, Giessen, Germany After life gained a foothold on Earth, it is assumed it spread rapidly over all niches where conditions were suitable

for originating life, so that the origin likely Verteporfin clinical trial occurred only once. But did it occur on Earth? As Earth was sterilized during the LHB, about 700 My after the formation of the solar system, seeding by lithopanspermia is a definite possibility (Horneck et al., 2008). If so, the question is what the place of origin could be in the solar system. Possible sources of life for lithopanspermia include Earth itself (before LHB), Mars, Venus (if it had a more benign climate than today) and the icy bodies in the outer solar system. The mechanics of lithopanspermia entail the problems of ejection, preservation during transfer and arrival. The ejection of pieces of the surface into space requires achieving at least the escape velocity of the parent body. Preservation during travel

from the parent body to the seeded “child body” appears to be a lesser problem. The arrival of spore-bearing meteorites is a more severe problem for airless bodies like the moon, because of the shock upon arrival, than for Earth where meteorites may survive through aerobraking. If we disregard the far-out bodies like Charon, and moons deep in the gravitational well of their planet like Europa, a likely parent body which remains is Ceres, which has had, or still has, an ocean more than 100 km deep, with hydrothermal activity at its rocky core (Castillo-Rogez et al., 2007). There, life may have originated early in the history of the solar system. Moreover, in this deep ocean it may well have survived the LHB.