Astrochemistry
- Georgina Griffiths
- Feb 2, 2021
- 4 min read
Astrochemistry, or cosmochemistry as it is referred to in some cases, is the study of molecular abundance and reactions within space as well as how the chemicals in space interact with different types of radiation, which is often referred to as spectroscopy. It is a relatively new area of study compared most other areas. Space science is often immediately associated with physics however this is not strictly the case, there are many areas of space science which focus on chemistry and biology including astrobotany and astrobiology.
Following the initial discovery of interstellar gas in 1904 by Johannes Hartmann the desire to understand the makeup and its properties. The conditions in space are highly contrary to those on earth and the gases in space can find themselves at anywhere between 10 and 10^6 K, and for a long time people thought that in this condition only atoms would be able to exist, however through much research we have learnt that this is not the case. Despite the 200 molecules already named there are still many more left to be discovered, however these molecules may require a new method of analysis to calculate what they may be.
Space science is often viewed as an unnecessary science as "we should focus on terrestrial issues" but, through space science, we can learn so much more about our world. It is understood that the US space program from the 60s caused a huge influx of money into the American economy, as well as leading to new scientific discoveries which have been used by us all today. One commonly overlooked item we have to the space race for is Goretex, commonly used for water resistant clothing, this uses Teflon in its production of PTFE which is the compound which gives Goretex its water resistant property.
Here are a two recent(-ish) discoveries in this area!!
"Formation of H3+ from ethane dication (CH2CH2^2+) induced by electron impact":
In a paper released in November 2020 a group of scientists have discovered a new method of producing H3+ (I apologise for the lack of subscript and superscript). H3+ is a molecule which is commonly used in interstellar chemistry in the formation of complex organic molecules. This is due to the ion being able to protonate (give a proton to) atoms. Until this paper had been released there had only been two known methods of creating this molecule. H3+ is found in star nurseries and is highly reactive, in fact it is so reactive that it is extremely rare to occur for very long on earth. It was first discovered in 1911 by J.J. Thompson while he was performing an early type of mass spectronomy. It has been found in most places scientists have looked in space so is in fact, in the grand scheme of things, highly abundant. The use of H3+ in research has lead to many new discoveries and learning new methods of producing it is highly useful.
They began with regular ethane (CH3CH3) and then "pulsed [an] electron beam" at the ethane, this excites the ethane molecule and causes a form of ethane ion to form. They discovered that H3+ was the most abundant product of this mechanism. This is most likely due to the potential energy surface being altered by the laser.
(the top bars indicate the abundance of each product)
There are a lot more details regarding this study on the paper, the link to which can be found in my referenced at the end of the article and will be colour coded for ease of use.
"Evidence for methane in Martian meteorites":
In a study published in June of 2015 a group of scientists describe the high likelihood of methane (CH4) being present in Martian meteorites. Rather than using a rover to investigate this the researchers discovered that when they crushed a meteorite they discovered that it released a highly methane rich component. The presence of this volatile gas could be indicative of life having existed on Mars or the potential for life, most likely microbial, to exist on Mars. This is due to the fact that CH4 is often produced by microorganisms on Earth. The life is most likely to be found in the subsurface as the temperatures are usually below 100ºC.
The components in a meteorite can be influenced by the atmosphere, the magmatism, the crustal processes and potential terrestrial(earthly) contamination. The amount of earthly contamination can be taken as minimal as the ratios of Argon and Oxygen gas to be closer to the atmosphere on Mars than the atmosphere on Earth. Compared to Earth there is significantly more methane in the Martian atmosphere which could be indicative of a methane generating mechanism in the Martian crust.
The ratios of methane in the meteorites are higher than the ratios in the atmosphere of Mars which implied that at least some of the methane in the meteorites does originate from the crust. In the same way this backs up the idea that there has been very little contamination from the earth as, if there had been contamination, you would expect the ratio of methane to lean toward the Earthly value rather than the Martian one.
Just like the previous study, more information regarding this study can be found via the link in the references section and will be colour coded for ease of use.
References:
"Space chemistry", from science and technology in action, accessed 5/1/21 http://sta.ie/lesson/space-chemistry
(Third image via) Zhang, Y., Ren, B., Yang, CL. et al. Formation of H3+ from ethane dication induced by electron impact. Commun Chem3, 160 (2020), accessed 5/1/21 https://doi.org/10.1038/s42004-020-00415-9
(Second image via) "Trihydrogen is the most important ion you’ve never heard of", by Janet Pelley, from chemical and engineering news, Accessed 5/1/21, https://cen.acs.org/physical-chemistry/astrochemistry/Trihydrogen-important-ion-ve-never/97/i23
"Grand Challenges in Astrochemistry", by Cristina Puzzarini, for Frontiers in... (astronomy and space science), accessed 5/1/21, https://www.frontiersin.org/articles/10.3389/fspas.2020.00019/full
Blamey, N., Parnell, J., McMahon, S. et al. Evidence for methane in Martian meteorites. Nat Commun6, 7399 (2015), accessed 6/1/21 https://doi.org/10.1038/ncomms8399
(Fourth image via)"Mars", from Britannica, accessed 6/1/21, https://www.britannica.com/place/Mars-planet
"Molecules at an exhibition" by John Emsley, Oxford University Press 1998, pages 132-133
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