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By Jay Jaganaath

Every day, we receive countless pieces of information about the weather and climate of the earth around us, from the dry Thar desert to the ever-humid Sunderbans. Technology on Earth has evolved to the point that we can even predict and quantify the activities of every part of the Earth’s atmosphere. However, have we ever considered how the atmosphere, and more importantly, the weather and climate might be present on other planets in the solar system, or even outside the solar system?

An emerging field of science, called exo-meteorology, aims to answer exactly that question. Exo- meteorology aims to to study different celestial bodies and extract information about their atmospheres through source material such as photographs, emitted radiation, orbital patterns. Most of the celestial bodies studied in exo-meteorology are either planets/satellites or stars.
The types of atmospheres of planets/satellites can be divided into the following categories: Quasi-Atmospheric, Earth-like and Giants.
Quasi-Atmospheric planets/satellites, like Mercury and Pluto, possess an extremely thin low-density atmosphere due to multiple factors such as a lower temperature and pressure conditions, small forces of gravity, lack of a strong magnetic field, small planetary masses and a proximity to their respective stars in their solar systems.  Such planets have a thin atmosphere made up by gases that are created through a breakdown of elements on the planet’s crust or through strong solar winds. However, such atmospheres are negligently small when compare to that of our Earth eg. Earths atmosphere is 1 atm while Mars’ atmosphere is a meager 0.00628 atm.
Earth-like planets/satellites possess planetary characteristics similar to that of the Earth eg. Kepler-186f, Venus and Saturn’s moon Titan. These bodies possess an earth-like force of gravity that is required to attract molecules to create a similar type of atmosphere. However, the nature of molecules that make up the Earth-like body’s surface might be radically different. For example, the Venusian atmosphere contains clouds of corrosive sulphuric acid and Titan’s atmosphere is composed of a thick collection of Nitrogen and Hydrocarbons such as methan and ethane.
Giants are planets that that possess a mass many orders greater than that of the Earth.
Giants, like Jupiter and Saturn, are planets that are majorly composed of elements and compounds that are typically gaseous on Earth eg. Hydrogen, Helium, Ammonia, etc.. Unlike the previously mentioned planets whose atmospheres account for a tiny proportion of their total masses, the atmospheres of the Giants account for a large part of their total masses, with there being no observable surface. Instead, a bottomless atmosphere is observed which culminates in a condensed or solidified of the the constituent atmosphere due to immense pressure eg. The centre of Jupiter is said to contain liquid metallic hydrogen and the centres of Uranus and Neptune are said to contain oceans of ammonia. In extremely high pressure environments, crystals can also be said to precipitate in the planet, as evidenced by the diamond rain that was reported in Saturn. Due to an overly exaggerated convection of gases in their atmosphere caused by extremely fast movement of constituent particles through the atmosphere’s boundless layers, such planets experience extremely fast winds and storms, the most notable being Jupiter’s 300-year old storm known as the Great Red Spot.
In addition to these celestial bodies, there exists information on the atmospheres of stars, called stellar atmospheres. Stars are usually contained of the photosphere,chromosphere, transition region and the corona.
The photosphere, which is the atmosphere’s lowest and coolest layer, is normally its only visible part. Light escaping from the surface of the star stems from this region and passes through the higher layers. The Sun’s photosphere has a temperature in the 5,770 K to 5,780 K range.Starspots, cool regions of disrupted magnetic field lie on the photosphere. Above the photosphere lies the chromosphere. This part of the atmosphere first cools down and then starts to heat up to about 10 times the temperature of the photosphere.  Above the chromosphere lies the transition region, where the temperature increases rapidly on a distance of only around 100 km. The outermost part of the stellar atmosphere is the corona, a tenuous plasma which has a temperature above one million Kelvin.
A study of the atmospheres of other extra-terrestrial atmospheres give us an insight as to how atmospheres are formed and how an atmosphere may have been formed on the Earth. In addition, it allows for us to scour the universe for an earth-like planet that can be a host to colonisation by humans in the event a cataclysmic event endangers the Earth.

Rohil Bahl