Panspermia hypothesis

The idea that microbes could migrate across the universe was supported by scientists with a worldwide reputation, such as H. von Helmholtz, W. Thomson (later Lord Kelvin) and Svante Arrhenius. This hypothesis was still accepted by Arrhenius in the year 1927, when he reported in the Zeitschrift fur Physikalische Chemie on his assumption that thermophilic bacteria could be transported within a few days from Venus (with a calculated surface temperature of 320 K) to the Earth by the radiation pressure of the sun (Arrhenius, 1927). The panspermia hypothesis, which seemed to have disappeared in the intervening decades, was reintroduced in the ideas of Francis Crick (Crick and Orgel, 1973). It still exists in a modified form (see Sect. 11.1.2.4). 

The panspermia hypothesis does not provide any explanation for the origin of life, as it presupposes the existence of functioning life forms. Two types of panspermia can be discussed, depending on the distances to be covered ... 

The result was that only a small fraction (10-6) of the spores which had been subjected to space conditions without protection survived. The same was true for those which were protected by a quartz disk or covered by a thin layer of clay. However, the survival rate of the spores mixed with the protective materials listed above was about five orders of magnitude higher, while almost 100% of those in the small cube survived (Horneck et al., 2002a). This experiment suggests that small pieces of rock, only a few centimetres in diameter, could act as a transport medium between certain heavenly bodies. However, the classical panspermia hypothesis, involving seeds of life on grains of dust, must be completely unreal. 

This model of the evolution of life on Earth does not preclude the possibility that life arrived on Earth fully formed from another body [the Panspermia Hypothesis (Horneck and Baumstark-Khan 2002 Wharton 2002 Napier 2004 Wallis and Wickramasinghe 2004)]. In this case, only a short-term temporary abode would be necessary for life to become established. 

Life in our Solar System could have started rapidly if the Panspermia Hypothesis is correct and life was seeded to Earth (and Mars and Europa ) from outside, or it may have taken hundreds of millions of years. At this time, only the crudest boundaries can be placed on the time for life to develop or the survival time for life after environmental conditions become hostile, but it may be on the order of hundreds of millions of years. 

Most of this discussion reveals an unstated assumption that the mental activity is not the product of the activity of the compound itself, but of one of its metabolites, or perhaps even the process of metabolism itself. The concept that the effect is due to a metabolite rather than the compound itself reminds me of the panspermia hypothesis for the origin of life that life did not originate on Earth, but came here through space from some other planet. This does not tell us how life originated, but simply moves the problem elsewhere. 

The possibility of the exogenous origin of life was considered by scientists as early as Helmholtz, and Arrhenius termed it panspermia, an idea with ancient roots. Today, the panspermia hypothesis has finally achieved some measure of scientific respectability. Although it remains the orthodox view that life evolved in situ on this planet and, possibly, many others, there is mounting evidence of at least some extraterrestrial input to the formative stages of planet-based biology. Here is a summary of the relevant facts (Hoover 2006, Russel and Hall 2006, Wickramas-inghe 2004) ... 

In the early twentieth century S. Arrheniusdeveloped his panspermia hypothesis. According to this theory life might have originated somewhere in the universe and would have spread out automatically. 

Since ancient times, philosophers have wondered whether life on Earth was seeded from elsewhere in the universe, an idea known as panspermia. It is generally agreed that meteorites and comets contain pre-biotic compounds that could have provided the raw material for life on Earth. A more contentious question is whether the comets might actually contain microscopic organisms, as proposed by Hoyle and Wickramasinghe (1981). This hypothesis has not been taken seriously by most scientists, although it is hard to disprove. 

---