In the darkness of space, comets are coming and going like pin-sized hairy reflectors of our sun's light.

I remember watching Halley's comet from North Head (on Sydney's North Shore) Sydney, 1986. Eery. There was about 4,000 silent people doing the same and finding a parking spot at 2:00 AM on this headland was rather difficult. North Head was a good spot to watch the comet, because apart from stars, there is not a speck of light to the east, where the comet could be seen. On the other hand, say South Head, there is the Sydney powerful lighthouse shining into the easterly night air. 
Some people had brought telescopes and I had my night-vision enhanced navy-grade binoculars. Halley's comet was a unique sight.

Comets are fascinating and this is why the Europeans landed an unmanned space module on comet 67P/Churyumov-Gerasimenko (also known as Rosetta — the name of the exploration mission — picture above). The size of the comet is 2.5 km x 2.5 km x 2.0 km for the small lobe and 4.1 km x 3.2 km x 1.3 km for the larger part. About 8 km from end to end.

The latest news from this comet is that some building blocks of life — amino acids — have been detected on its surface. Analysis done by Rosetta's probe are very specific. But this is not a proof that life on earth comes from comets. It's possible that when the solar system was still in its infancy, one planet did not form or disintegrated into what is known as the asteroid belt (https://en.wikipedia.org/wiki/Asteroid_belt) around the sun between the orbit of Mars and Jupiter. It is also possible that these comets have been captured from outer space by the sun's gravity. All this tells us that all the basic elements to form the amino acids are present in the greater universe and subsequent chemical reaction have also happened in the ether while comets gathered minute quantities of these various gases and molecules on their frozen water travels. 

Planet earth, with water and all the elements for building the blocks of life, has also been a prominent site for the next development of chemicals into amino-acids. There are very cold moons of Saturn such as Titan with lakes and rivers of methane. Methane is a basic hydrocarbon with no oxygen. Though methane is part and parcel of bio-activity (organic compound), it is not so exclusively.

The presence of the amino acid glycine on the comet 67P/Churyumov-Gerasimenko is quite spectacular. Glycine (abbreviated as Gly or G) is the smallest of the 20 amino acids commonly found in proteins, and indeed is the smallest possible protein (having a hydrogen substituent as its side-chain). The formula is NH2CH2COOH. Its codons (sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule) are GGU, GGC, GGA, GGG of the genetic code. Thus glycine is a very important part of life.

Glycine is a colorless, sweet-tasting crystalline solid. It is unique among the proteinogenic amino acids in that it is achiral (does not have a mirror image molecule). It can fit into hydrophilic or hydrophobic environments, due to its minimal side chain of only one hydrogen atom. The acyl radical is glycyl.    

Thus our genes are dependent on glycine. The fact that it is an achiral molecule is also very important.   

Another biochemical that appears on Comet 67P/Churyumov-Gerasimenko is methyl isocyanate...

After the first touchdown at Agilkia, the gas-sniffing instruments Ptolemy and COSAC analysed samples entering the lander and determined the chemical composition of the comet’s gas and dust, important tracers of the raw materials present in the early Solar System.

COSAC analysed samples entering tubes at the bottom of the lander kicked up during the first touchdown, dominated by the volatile ingredients of ice-poor dust grains. This revealed a suite of 16 organic compounds comprising numerous carbon and nitrogen-rich compounds, including four compounds – methyl isocyanate, acetone, propionaldehyde and acetamide – that have never before been detected in comets.

Meanwhile, Ptolemy sampled ambient gas entering tubes at the top of the lander and detected the main components of coma gases – water vapour, carbon monoxide and carbon dioxide, along with smaller amounts of carbon-bearing organic compounds, including formaldehyde.

Importantly, some of these compounds detected by Ptolemy and COSAC play a key role in the prebiotic synthesis of amino acids, sugars and nucleobases: the ingredients for life. For example, formaldehyde is implicated in the formation of ribose, which ultimately features in molecules like DNA.

 

read more: http://blogs.esa.int/rosetta/2015/07/30/science-on-the-surface-of-a-comet/ 

Methyl isocyanate is the gas that killed about 20,000 people (nearly 4000 instantly) and injured more than 500,000 people in a Union Carbide accident in Bhopal, India in 1984 —two years before Halley's comet latest visit. Methyl isocyanate, though highly dangerous, is a product used to manufacture insecticides — most of them banned around the world nowadays. 

So we have good indication that even in the solar system, which is one of billion billions in the universe, there are building blocks of life as well as dangerous organic compounds. 

The next step is that of aggregation of the building blocks of life and life's evolution which took specific timeframes on planet earth. 

The probe landed in this corner of the comet after a malfunction. Who knows is this was not an accidental bonus. The probe was designed to land in the sunny part of the comet, in order to maintain the level of electricity through its solar panels. But having landed in a darker part might have actually exposed a richer concentration, though minute, of molecules similar to those building life on earth. 

Despite being a hydrocarbon organic compound, Methyl isocyanate is a strong poison to human life. It has been thought of as a chemical weapon. As well, MIC (methyl isocyanate) reacts with water, giving off heat and producing methylamine and carbon dioxide. Methylamine is a controlled substance as a List 1 precursor chemical by the United States Drug Enforcement Administration due to its use in the production of methamphetamine.   
 Bayer also had an accident with Methyl isocyanate in 2008 and since then has stopped the manufactured of MIC and the derived insecticides. The Environmental Protection Agency (USA) cancelled registration of Aldicarb, a carbamate pesticide known commercially as TEMIK that is produced using MIC. Shortly afterwards, Bayer announced that production of certain other carbamate pesticides was no longer economically viable for the company and would cease at the end of 2012. The main problem was the storage of methyl isocyanate. 

Considering that 0.02 part per million of methyl isocyanate can be dangerous to humans, the Bhopal plant in India had around 70 tonnes of the product in underground storage tanks. About 30 tonnes escaped into the air, creating the biggest chemical disaster so far. The balance of the methyl isocyanate, possibly on the verge of escaping as well, had to be carefully "reacted" into pesticide in order to eliminate the potency. 

The fascinating fact here is that the comet 67P contains both some of the amino acids, building blocks of life and one of its major killer molecule within.

Just letting you know.


Gus Leonisky

Comet watcher...