Jovian moons

Io is one of the most interesting objects in planetary research. However, it is completely irrelevant to the biogenesis problem, in complete contrast to the Jovian moon Europa. 

Fig. 3.2 The three possible models for the inner structure of the Jovian moon Europa model 1 has a thin layer of ice at the surface, model 2 is the ice-water model and model 3 involves a thick ice layer...

Moore (1998) suggested that the data available could be interpreted in terms of an ice crust 10-15 km thick. Christopher Chyba from the SETI Institute (Mountain View, California) has published articles in Nature (2000), the Proceedings of the National Academy of Sciences (2001a) and in Science (2001b) in which he suggests that a detailed study of this Jovian moon is necessary he discusses the possibility of a complex ecosystem, nourished by the radiation coming from outer space, on or in the ice layers of the moon. The planned Europa orbiter mission may provide certainty on this, but at least another five years of uncertainty lie ahead. The use of a submersible robot to study the (possible) ocean layer and its floor has been discussed. 

These two Jovian moons are in some respects quite similar. They probably consist of rocky material and frozen water (in a ratio close to 1 1) and, in contrast to Europa, are covered by a large number of craters caused by collisions with other heavenly bodies. 

Why does only Titan have such a massive atmosphere, in contrast to the other similarly sized Jovian moons (which are closer to the sun, but have an escape... 

The purine base guanine is also formed in concentrated solutions of ammonium cyanide, i.e., the same substance which became known from Or6 s adenine synthesis. Or6, as well as Stanley Miller, was involved in a new series of experiments (Levi et al., 1999). The yield of guanine is, however, 10 10 times lower than that of adenine surprisingly, the synthesis is just as effective at 253 K as at 353 K. Low temperatures seem conceivable in certain parts of Earth as well as on the Jovian moon Europa (see Sect. 3.1.5) or in the Murchison meteorite. 

The current models of the Sun suggest that its luminosity would have been some 20-30 per cent lower than its present value during the early part of the formation of the Earth. After the enormous temperatures of the Hadean period, the early precambrian may have been cooler, requiring prebiotic chemistry to occur below a layer of ice, perhaps heated by volcanic activity such as that found in geothermal vents. A layer of ice several hundreds of kilometres thick may have formed over the entire surface of the early Earth, providing protection from UV radiation and some global warming - conditions such as these may exist on the Jovian moon Europa. 

Figure 6.1. The Jovian moon lo deep ultraviolet (UV) photolysis of its methane atmosphere proceeds with electron ejection, generating the molecular ion of methane (see color insert). NASA JPL Galileo program image from Voyager 1, http //www.jpl.nasa.gov/galileo/io/...

The Jovian moon, lo, shows an orange hue (Fig. 6.1), which may be due to long-chain alkane radical cations. The atmosphere of lo consists mostly of methane deep UV photolysis proceeds with electron ejection thus, the molecular ion of methane was perhaps the earliest organic radical cation, generated by solar irradiation aeons ago. 

Can one be so sure about this invariance concept only because we can never test this prediction Not really. The Jovian moons are within our reach and Mars is still in contention as a life-supporting rock, so one must consider the idea in principle testable. Life will be the same and everybody who is searching for life elsewhere knows it intuitively, because they are looking with the methods it takes to detect our kind of life. They are all unwitting supporters of the invariance concept of the Genomic Potential Hypothesis. 

Sulfur can form halogen compounds and nitrides. The nitrogen compounds are found as interstellar molecules and chlorides postulated on the Jovian moon, lo, but these compounds do not appear to be a significant part of biogeochemical cycles on the Earth. 

The active volcanoes of the Jovian moon lo release large quantities of sulfur and other materials (Spencer and Schneider, 1996) that recover the surface at a rapid rate and maintain a tenuous atmosphere. This sulfur is largely as sulfur dioxide, which is also found as condensate that covers some three-quarters of the surface. However, sulfur is also found as elemental sulfur, with perhaps traces of hydrogen sulfide (Russell and Kivelson, 2001 Zolotov and Fegley, 1998). Low pressures in the atmosphere of lo mean that sulfur can remain in seemingly exotic forms such as sulfur monoxide (SO), which has been calculated to have an SO/SO2 ratio of 3-10% (Zolotov and Fegley, 1998). Others suggest that OSOSO, and its cation, are likely present in the lo s atmosphere (Cacace et al., 2001). 

Figure 21 Radiolytic sulfur cycling on the Jovian moon Europa with reaction rates marked numerically as reaction efficiencies. The transient sulfinic acid is circled as an intermediate (source Carlson et aL, 2002).

The results we obtained at 77 K, a temperature more appropriate to the jovian moons, are qualitatively and quantitatively the same as those at 16 K. Moreover, after implantation, we warmed the samples and obtained spectra at progressively higher temperatures Carbon dioxide is still there at 140 K when water ice completed the crystallization process, and it remains trapped until water is lost by sublimation. This gives us confidence that our findings can be extrapolated to environments with a large range of temperatures. " ... 

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