Exoplanetary Atmospheres and How to Understand Them

Six stories that examine atmospheres, both here on Earth and on exoplanets.

IMAGE: The early atmospheres of rocky planets are thought to form mostly from gases released from the surface of the planet as a result of the intense heating during the accretion of planetary building blocks and later volcanic activity early in the planet’s development. CREDIT: Dan Durda/Southwest Research Institute

Let’s start with Earth, where a team of scientists from UC Santa Cruz baked meteorites at 1200 degrees Celsius and then sampled the resulting gases produced using a mass spectrometer. Overall, water was predominant, followed by large amounts of carbon monoxide and carbon dioxide, and then smaller amounts of hydrogen and hydrogen sulfide.

These results are interesting because up until this research, most atmospheric models assumed gases with solar abundances; in other words, heavy on hydrogen and helium. As coauthor Myriam Telus explains: Based on outgassing from meteorites, however, you would expect water vapor to be the dominant gas, followed by carbon monoxide and carbon dioxide. Using solar abundances is fine for large, Jupiter-size planets that acquire their atmospheres from the solar nebula, but smaller planets are thought to get their atmospheres more from outgassing.

Putting it another way, the atmospheres of rocky planets were thought to derive mostly from the gas released due to the intense heat of pulling together all the building blocks and material as well as later volcanic eruptions and outgassing. And this research, which is published in Nature Astronomy, shows that the primitive rocky material in our own solar system…