How can analytical chemistry techniques be used to find habitable planets or extra-terrestrial life?
Pablo Pinel-Morell
In chemistry there are many tests that let us know of the presence of certain elements or functional groups, for example the test for hydrogen or carbon dioxide, which involve simple apparatus and straightforward methods. However, there are different analytical tests which often give more precise results on the chemical makeup of a substance but require more expensive and complicated equipment. These techniques are then often put on spectrums where chemists can then decipher not only the molecular formula but also the structure of the sample. Furthermore, mass spectrometry, spectroscopy and chromatography are now commonly used in outer space to analyse planets and stars. This essay will examine how these techniques have been used in space exploration and to what extent they can help in the detection of extra-terrestrial life or planets that can support life. A mass spectrometer measures the masses of atoms and molecules in a substance by first ionizing them and putting them through a powerful magnetic field, the greater the mass of a particular gas, the less its deflection in the magnetic field. These ionized molecules are then split up into beams of different molecular weight which are then measured (PMJ, 1957). There are other types of mass spectrometers which use other forms of differentiating the molecules by mass, such as the time of flight mass spectrometer. The NASA Viking mission to Mars was the first to use in situ life detection and a mass spectrometer on another planet (Chou, 2021). The payload of the lander contained various experiments with two gas chromatography – mass spectrometers. The gas chromatography instrument works by carrying gases that are heated through a column with an inert gas (such as helium); the separated
substances then flow into the mass spectrometer, where they are ionized and then analysed. However, these highly capable mass spectrometers failed to detect any organic compounds (Biemann et al.,1977, as cited in Chou, 2021). In 2013 the Curiosity rover ’ s SAM (surface analysis of Mars) inlet detected chlorates and perchlorates using the GC-MS combination, compounds which reflect many planetary processes that earth has gone through (Clark,
Figure 1: A simple diagram of a GC-MS
2021). SAM also observed simple chlorohydrocarbons which could be consistent with organic carbon (Grotzinger, 2013) (MING, 2013). The Viking and Curiosity missions both displayed how analytical chemistry can be used on another planet to find evidence for the building blocks of life. Though the mass spectrometer and gas chromatography combination has been deemed useful in the SAM unit of the Mars rover, it has some constraints. Firstly, the process requires prior context on what is expected to be found; it is also designed for use on the Terran spectral database, so it is more difficult to find, analyse and identify agnostic biosignatures (Chou, 2021). Mass spectrometers are also heavily limited when performing in situ missions as they are restricted to a certain weight and do not have the same
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