Complex and subtle chemical reactions require a liquid medium in which to occur. Liquids cannot exist isolated in space or on bodies without gaseous pressure pressing down on a solid surface. Of all the known objects in our Solar System, only the earth (definitely europa, ganymede, titan, Enceladus and Trton (the last five probably) have the conditions needed for liquid to exist and the substance that can be a liquid under the prevailing conditions. Life may be limited to just these seven bodies in the solar System. Of course, this doesn't mean that there is life on Titan, Enceladus, ganymede, europa or Triton. On Titan, there may not be a large amount of liquid.
The Blood of the, earth: An Essay on Magic and peak
A recent probe discovered what look like small lakes on the internship surface. Saturn's moon, Enceladus, has shown evidence of geysers of water coming from liquid water below the surface. Jupiter's satellite, europa has no life atmosphere. It is covered by solid water ice that shows evidence of liquid welling up from below before freezing in the cold temperatures. It is likely that liquid water exists below the ice. This is another world that will be explored for life. Another of Jupiter's satellites, ganymede, may have a similar makeup. Neptune's satellite, trton has geysers of liquid nitrogen which indicates the presence of that substance under the surface. So, of all the bodies in the solar System, one (the earth) definitely has liquid on the surface, and five others (Titan, Enceladus, europa, ganymede and Triton) may have liquid on or below the surface. No wonder we haven't seen any martians or Venusians! Recap and Conclusion Let's just recap on the logic of all this: Life requires complex and subtle chemical reactions.
These conditions are right for liquid water to exist and, of course, it does. Mars has a very thin atmosphere business made up of Carbon dioxide and Nitrogen. Neither the pressure or temperature (-50C) on the surface is sufficient for either to exist as a liquid. No liquid has ever been observed on Mars although there is evidence that it existed in the past and may exist below the surface. Life may exist on Mars in some primitive or suspended form in areas where there is evidence of past water. On, titan, the atmosphere is Nitrogen and Methane and the temperature is -150C. With these conditions, it would be possible for liquid Methane to exist on the surface of Titan. The Orange atmosphere hides the surface.
Liquids could only exist on father's these five objects; this is not the same as saying liquids do exist on these objects. That depends on the chemistry, pressure and temperature. On, venus the atmosphere is very thick, but the temperature is over 700C. Nothing that exists in the atmosphere of Venus is liquid under the conditions found on the surface of Venus. Carbon dioxide and Sulphuric Acid (the two constituents of the venusian atmosphere) are both gases under those conditions. Venus is surrounded by thick clouds but infra red and radar measurements indicate a bone dry surface. On the, earth, the atmosphere is made up of Nitrogen, Oxygen, Argon, carbon dioxide and Water Vapour. The average temperature is about 20C.
The remaining major planets (Mercury, venus, earth, mars - the. Terrestrial Planets their satellites and the minor planets are smaller, rockier bodies. Of these, mercury and most of the satellites (like our moon, jupiter's io and Ganymede) are small solid objects with no atmospheres. The minor planets (e.g. Ceres, Chiron, vesta) and kuiper Belt Objects (e.g. Pluto, sedna) are rocky, metallic or icy bodies with no significant atmosphere. Four of the remaining bodies in the solar System have atmospheres. These are venus, the earth, mars and Saturn's largest moon, titan. Jupiter's moon, europa, is covered by ices and there is some evidence of liquid below the surface.
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All stars are made of gas. The temperature and pressure of even the coolest star ensures that all substances within the star are gaseous. Liquids tex can only exist as the 'filling' of a sandwich. What do i mean by this? Liquids require a solid surface to hold them and a gaseous or solid topping to keep them from evaporating away. A body like the moon which has no atmosphere cannot have any liquid on its surface.
Without atmospheric pressure to keep it there, a lunar liquid would quickly essay (in the geological sense) leak away and be lost. The only places in the Universe where liquids can exist are solid planets with atmospheres or planets where the liquid is covered by its frozen form. In the solar System there are only five places where liquids could exist. The sun is wholly gaseous. Jupiter, saturn, Uranus, and Neptune are giant, mainly gaseous major planets with no solid surfaces (the. Jovian Planets or, gas giants ).
In gases the molecules are flying around free of each other. When solids are mixed they tend not to react together (unless it's a violent reaction like in gunpowder). Gases mix very thoroughly and any reaction goes to completion (in other words there is no subtlety when gases react). Reactions in liquids, however, can be controlled by things like concentration, acidity, and temperature. Liquids provide an excellent medium for complex and subtle chemical reactions. In fact it is difficult to see how the complex reactions of life can occur in anything other than a liquid medium.
Of course, this could change with new evidence. Unfortunately, the liquid state is the rarest in the Universe. In the depths of space, matter exists as either solid (dust, meteors, asteroids) or as gas (nebulae). Liquids are always 'leaking'. In the vacuum of space there is nothing to hold a liquid together. A drop of liquid would quickly evaporate. In the rest of the Universe, the most common unit is the star.
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This is no accident. Carbon is the only atom capable of forming large complex molecules. The chemistry of carbon compounds london is called. The chemical reactions of life are subtle and complex. Let us look at the conditions necessary for complex chemical reactions to occur. In nature, matter is found in three states: online gas, liquid and solid. In solids the molecules are held together in fixed positions relative to each other. In liquids, the molecules are close together but not rigidly held: they can slide over and around each other.
Essentially, this is a chemical definition of life. Molecules pass into the organism and are built up to dissertation complex molecules distinctive of the organism by a series of chemical reactions. Waste products from this process are passed back out again. Many people believe that life involves something else apart from chemistry. This is a piece of speculation that I will ignore since i know nothing about. The above chemical definition of life actually imposes severe limits on where life can be expected. Life on Earth is made up of complex molecules based.
Within a cell, the material inside the virus uses the cell's chemistry to reproduce itself. So what we have to find is a working definition that will include all living things but not ones that are not living. That is actually very difficult. The one i will use for this essay is as follows. A living organism is a system that can interact with its environment, exchanging material with the outside, and capable of reproducing itself.
This limits the number of conclusions we can draw. The more examples of a phenomenon that you real have, the more you can deduce by comparing. I know that there are many people who believe that. Ufo's represent intelligent visitors from other worlds. In this essay i will assume that ufo's are not intelligent visitors from other worlds. I may be proved wrong tomorrow. The next thing to do is to define life. How can we tell a living thing from something that doesn't live. Sometimes it's easy (a tiger and a rock).
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KryssTal : Extraterrestrial Life, the answer to the above question. This essay is not an essay of answers because nobody knows the answer. What I want to do is speculate. My speculation will be controlled and based on the knowledge we have at present. Like all science, everything I say in this essay could be proved wrong by a new theory or discovery tomorrow. However, the path that we follow will be full of interesting ideas that, i hope, will stimulate the reader. The reason I talk about extraterrestrial life is because there is strong evidence that all life on this planet has a common origin. Chemically and genetically there are evolutionary links between all organisms that more or less reflect the more traditional attempts at linking diary them. This means, of course, that we have only one example of life to study.