Cometary collisions

Others 1 CO, C02, C302i H202, H2C03, N2H4 HNCO, NH2CONH2, NH2CONHCONH2 (CH2)sN4 HMT, (-CH2-0-)n POM 

NH2CH2COOH (Glycine) NH2CH(CH3)COOH (Alanine) CH3CH2CH(NH2)COOH (a ABA) CH3CH(NH2)CH2COOH ( 3 ABA) (CH2NH2)(CH3)CHCOOH (AIBA) 

The analysis of the laboratory ice experiments reveals a diverse array of bio-logical-looking molecules with the potential to seed life. Cometary collisions with planets could deliver these molecules to a primitive Earth or indeed to all planets within the solar system. The frequency of the collisions depends somewhat on the local star and the structure of the solar system forming around it. 

The formation of the planets around the proto-sun initially started as a simple accretion process, aggregating small particles to form larger particles. This process was common to all planets, even the gas giants Jupiter and Saturn and to a lesser extent Neptune and Uranus. The planetesimals form at different rates and as soon as Jupiter and Saturn had reached a critical mass they were able to trap large amounts of hydrogen and helium from the solar nebula. The centres of Jupiter 

A new reservoir of comets may have formed at around 5 AU in a local orbit around Jupiter or at least perturbed by its gravitational attraction. A comet close to Jupiter would simply have been captured, delivering its chemical payload to the ever-increasing gas giant. Some comets would merely have been deflected towards the inner terrestrial planets, delivering a similar payload of water and processed molecules. Cometary impacts such as the spectacular collision of the comet Shoemaker-Levy 9 with Jupiter would have been common in the early formation phase of the solar system but with a much greater collision rate. Calculations of the expected collision rate between the Earth and potential small comets deflected from the snow line may have been sufficient to provide the Earth with its entire 

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Other events, evidence of which has not yet been detected in polar ice, may also eventually serve as useful time markers in the future. Large meteors or meteor swarms that ablated in the upper atmosphere may have left a significant chemical impact on succeeding snowfalls. The same may be true for cometary collisions or brushes with a comet s tail. As with ancient volcanic eruptions, such events need not have been historically documented. If identified and accurately dated in one ice core, these events will serve as useful time horizons in other cores. 

Urey, H. C., Cometary Collisions and Geological Periods, Nature 242, 32, 1973. 

A second interpretation of carbonaceous chondrites is as primary condensates of the solar nebula. By this view, their hydrolytic alteration is due to melting in cometary nuclei during close passes with the Sun, or due to transient heating events by shock waves or collisions (McSween, 1999). Other carbonaceous chondrites show metamorphic alteration with minerals similar to those in Earth formed during deep burial under elevated temperatures and pressures (Brearley, 1999). Like soils and paleosols on Earth and Mars, carbonaceous chondrites demonstrate the great antiquity of hydrolytic weathering in dilute acidic solutions, presumably of carbonic acid derived from water vapor and CO2. These remain the principal gases released from volcanoes, and soils remain important buffers for this environmental acid. 

Several reviewers have discussed the fundamental role played by dust in the physical processes occurring in planetary magnetospheres, leading to tori at Jupiter and Saturn and to planetary rings at Jupiter, Saturn, Uranus, and Neptune via sputtering of surfaces (Johnson, 1994 Johnson, 1996 Johnson et al, 1998). Plasma-dust interactions occur in the cometary atmosphere via a combination of solar radiation pressure, plasma drag (inelastic ion-surface collisions), and electromagnetic forces (Whipple, 1981 Whipple et al, 1985 Hartquist et al. 

Collisions between comets and planets have occurred often during the evolution of the solar system. Cometary impacts on early Earth may have deposited a substantial amount of water to the Earth. The masses of lost and retained water after the impacts of comets and asteroids on oceans of various depths were studied by Svetsov, 2009 [330], The bombardment of an atmosphereless planet by fast asteroids can wipe out the most part of an ocean. Because of their mass loss during perihelion passage, it is difficult to predict cometary orbits with high precision. Therefore an impact of a comet on a planet cannot be predicted precisely. 

As we have already pointed out, comets may have been very important for the Earth and terrestrial planets because they deposited during collisions considerable amounts of water on the surfaces of these planets. On March 18, 1988 dark features on nine consecutive photographs were observed on Venus. Since film defects and other interferences (e.g. from an artificial Earth satellite or interplanetary object) can be ruled out, it is highly probable that this event was an impact of a small cometary like object that took place on the upper haze layer of the dense Venusian atmosphere. Because such an object consists mainly of water, evaporation of H2SO4 particles occurred which decreased the albedo at the point of entrance and therefore a dark feature appeared (Kolovos, Varvoglis and Pylarinou, 1991 [189]). 

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