The present-day bulk elemental composition of an exoplanet can provide insight into a planet’s formation and evolutionary history.
![C/O ratio as a function of metallicity [M/H] as given in Table 4. Planets observed with direct spectroscopy are shown as blue circles, planets observed with eclipse spectroscopy as magenta squares, and planets observed with transit spectroscopy as gold diamonds. Ultra-hot Jupiters are labeled as stars. -- astro-ph.EP](https://i0.wp.com/astrobiology.com/wp-content/uploads/2025/11/The-Library-of-Exoplanet-Atmospheric-Composition.png?resize=1200%2C720&ssl=1)
The present-day bulk elemental composition of an exoplanet can provide insight into a planet’s formation and evolutionary history.