Organic Chemistry Across the Universe
Extraterrestrial Transformation

Why recreate the reaction conditions found in space in labs on Earth?

To recreate the reactions that occur in space is to confirm the evidence of spectroscopy. We need to be able to identify a molecule unambiguously comparing it to a known spectrum of the molecule. The results of laboratory reactions also pre-empt which new molecules might be being formed in similar reactions in space, but which have not yet been detected from their radiation emissions. Referencing the evidence for extraterrestrial organic molecules is like a game of pairs. One either has an unidentified extraterrestrial spectrum or a laboratory spectrum and the race is on to find its partner. The majority of spectral data, which is held in databases, gives the resonance frequencies of molecules in their liquid phase. This is due to the majority of reactions and spectra taking place in the liquid phase on Earth. Molecules behave differently in a different phase and so their spectrum appears different. It is similar to the way a photograph will look different taken in a change of light. The emissions of gas phase space molecules have to be compared with spectra from molecules in the gas phase, which are recreated in the laboratory here on Earth(18). To recreate the extreme conditions found in space is no small task. Experiments have centred upon the reinaction of reactions performed on ice grains inside dense clouds. Ice grains form when gaseous molecules of water, methanol, hydrocarbons and other simple compounds freeze onto tiny particles of silicate(7),(19). This starting material has been created in the lab using custom built refrigerators and pumps able to form the high vacuum and low temperature found in the interstellar medium, fig.7. These ices are then bathed in ultra violet light for a couple of hours, imitating starlight. The formation of products is monitored by IR spectroscopy during the reaction to watch how long it takes for more complex molecules to form.

The formation of an ice grain in space.
Fig.6(4)



The experimental equipment used to create an ice grain in the lab.



Fig.7(4)

Twenty percent of the cosmically available carbon is bound up in the structures of Polyatomic Aromatic Hydrocarbons(7). As there is a search for life giving organic molecules in the galaxy. Organic molecules are carbon based and the question is where can we get this carbon? The answer is PAH's. The reactions of PAH's have been studied as a likely source of these life molecules. Ice grains containing PAH's were synthesised and subjected to UV radiation in the lab.



In the reaction about 5% of the PAH's frozen in the ice transformed into the Ether, Alcohol, ketone or Hn-PAH related Polyatomic aromatic hydrocarbons(7). This small amount would still be significant in reactions in space. The UV light used in the experiment was exposed to the ices for an equivalent time scale of 105 years in a dense interstellar cloud(7). We can imagine the slowness of reactions in space and how long it takes to make any changes to the composition of the galaxy. The Molecules that are produced can account for some previously unidentified IR bands and these forms of oxidised PAH's have also been found in the Murchison meteorite(2).

Meteorites

Religious cults predicting the end of the world sometimes look to the sky as a source of inspiration. A hurling meteorite will pitch the Earth into catastrophic disorder and humankind will be obliterated like the dinosaurs. It could happen, but we don't know how much of a warning we are likely to get, like the family in England that had a meteorite dig a hole in their back garden in the middle of the night(20). About a hundred tonnes of space debris falls to the Earth every year(19). In 1969 one such visitor was the Murchison meteorite who landed in central Australia(2). Inside this meteorite's body of carbonaceous chondrites were a multitude of goodies. Seventy-four amino acids, aliphatic and aromatic hydrocarbons, carboxylic acids and nitrogen hetrocycles were among the organic molecules(2). The big question is, has the meteorite been contaminated by molecules already on the Earth or are they purely extraterrestrial? It was thought that all organic matter would be vaporised when it passed through the Earth's atmosphere but Delsemme disagrees saying(2),

'The argument that the heat of the impacts with the Earth is going to destroy all the organic material, is bought to rest when one realises that a large fraction of it is brought to Earth by cometary dust. This dust visible in the beautiful tails of comets, is braked by the upper atmosphere and gently bought to the ground.'

But could the contents of a meteorite survive? We can not say, but need more evidence from other sources to prove that these same molecules exist in space. Amino acids and PAH's have been created in the laboratory from ice grains but amino acids have still not been detected in the tails of comets or radiating their personal telephone numbers from any other stellar object. This is why the detection of Glycolaldehyde is so important. It points to the possibilities that with more scouring of the galaxy with telescopes amino acids could be found. There was a time in the evolution of life on the earth that the first Cell was formed. Living organisms needed to protect the chemistry going on within their forms from interference from the outside environment. They produced boundary structures to surround their life factories and keep them safe(21). This design is known as the cell. How did it first evolve? Ancient biological organisms have been studied in rocks and they have cellular structures. The Murchison meteorite gives us an idea of how of how these cells first formed(8). When material from the meteorite was immersed in water membranous structures like primitive cells formed. They created a microenvironment like a bubble. The same structure has been formed in the lab using mixtures of compounds produced by irradiating ice grains. Again the mixture forms a cell like structure. This suggests that organic matter from dense interstellar clouds when put into the right conditions, like on a watery planet, can form cells. These cells are able convert energy as they change UV radiation into light as they fluoresce under an UV lamp.

Fig.8(4)





Fig.9(4) and Fig.10(4)

The primitive cells are shown in the photographs fig.8-10. The cells are fluorescing green due to a dye being captured inside their structure like air in a bubble. The trapping of this dye is evidence for the space inside the cell being cut off from the outside environment. The cells are formed by molecules arranging themselves into a membrane with hydrophobic, water hating, parts of the molecules hiding from the water in the inside surface of the bubble.



Start Contents Abstract Introduction Sugar in space
Spectroscopy Polyatomic Aromatic Hydrocarbon Simulating Space Conclusion
References