For my PhD thesis at Valongo Observatory (UFRJ), I have chosen to study the atmospheres of exoplanets, i.e. planets outside the Solar System. To this day there are more than 4000 confirmed exoplanets, some similar to the Earth, other similar to Jupiter, Saturn, Neptune, and some different from anything we have ever imagined. I do not choose the kind of exoplanets I work with. I work with a small sample and I will tell you why.
I study the planets that have an available transmission spectra. A transmission spectrum is obtained in a certain lineup configuration, where the planet can pass in front of and behind the star. When in front of the star, it blocks the portion of star light according to the planet size. This portion of light will pass through the planet's atmosphere, producing a transmission spectrum. This is my initial object of study.
However, this spectral resolution is very low. This is why we use them to model synthetic spectra, and infer the atmospheric properties of each planet, such as its temperature, surface gravity, pressure, chemical abundances and presence of clouds. By understanding an exoplanet's atmosphere, one can learn about its formation and even verify if it could be a potential habitat for the origin and evolution of life.
A molecule that is produced by life is called a biosignature, such as O2, O3 and CH4 on Earth. But keep in mind that these molecules in other planets are not necessarily proof of life! The Astrobiology field needs to further investigate each and every case. That is why it is such a big and multidisciplinary field!
Further updates on my work will be posted here and possibly on my Twitter page, so make sure you follow me there as well.