We take too much for granted when we are looking at terrestrial materials such as rocks and then assume that they are representative for those on other bodies within our solar system in general:
Conditions on Earth scarcely resemble those elsewhere in our own solar system. We live on a wet and tepid exception to the chemical and physical norms of the planets that contain most of the solar sysytems mass. Being made largely of water like the rest of the life on Earth, we think nothing of life’s inorganic substrate being the product of wet chemistry…
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Earthly quartz and feldspars, micas and clays, all contain water and have been re-arranged by it. Likewise, compounds that are decomposed by water and elements that react vigorously with it are largely alien to the surface of the Earth. Not only have we never seen them in the state of nature, but they scarcely figure in our imagined view of the chemistry that gave rise to life…
To plug the gaps in our knowledge and to overcome our (understandable) failure of imagination, we would have to send out a fleet of robotic spacecraft to collect samples from the various rocky bodies in the solar system. A systematic analysis of those samples would offer some important insights in how materials develop and self-organize in and on rocky planets and moons that are solid like the Earth but unlike it are non-aqueous. These results would in turn provide some clues on how emergent and autocatalytic processes can lead from inorganic to organic chemistry and maybe even to life, under conditions that are radically different from those on Earth.
All a chemist has to do in order to realize this is look at how many reagent jars in his or her lab are labelled [Reagent].xH2O, where x is some even number between 2 and 12, usually.
Non-aqueous chemistry is always a pain in the rear because of Earth’s environemtnal conditions.
Current thinking says that Earth has an unusual water based chemistry because it has oxygen generating life-forms. Without oxygen, ozone does not form and without ozone UV radiation will destroy significant amounts of water over geological time rendering the planet dry. Without water, composition of the earths rocks would grow more rigid and tectonic activity would grind to a halt. Without tectonic activity, the conversion of CO2 to limestone via chemical and biological action would strip all the carbon out of the biosphere. Without carbon there is no oxygen generating life-forms.
And round and round it goes.
The presence of vast amounts of diatomic oxygen also makes the earth a unique chemical environment as does the continual churning of the earths crust. We might find radically different minerals on worlds that have sat for billions of years without tectonic activity, water or free oxygen. We might find giant crystals of gallium or other related elements that grew incredibly slowly by the migration of atoms.
There are more feedback loops of course – without organic life and its (waste) products, Earth wouldn’t be in the so-called habitable zone of our solar systems, no matter where the Earth has it’s orbit in our solar system and what the ‘astrobiologists’ say.
Ralf Goergens,
Earth wouldn’t be in the so-called habitable zone of our solar systems, no matter where the Earth has it’s orbit in our solar system and what the ‘astrobiologists’ say.
Huh?
Sorry, I should have been a bit more explicit:
Astrobiologists have a theory about ‘habitable zones’ around the sun of a solar system. Depending on the energy output of the stAr in question, the habitable zone will be of a certain extent. But the point is, without the kind of life we have on Earth as well as the resulting athmosphere, Earth wouldn’t retain enough heat from sunlight, and therefore wouldn’t be warm enough to be a planet inside what the astrobiologists call a habitable zone. Kind of embarrassing, if you consider that their only basis for theorizing about habitable zones is the Earth in the first place.