Hazy Sunsets on Saturn's Titan Reveal Complexity of Exoplanet Atmospheres

Scientists may have discovered a new way to understand the atmospheres of exoplanets. Working with data from NASA's Cassini, researchers have examined Saturn's hazy moon, Titan, in order to act as a stand-in for other exoplanets in order to develop a new and possibly more effective technique.

The new method revolves around sunsets. Light from sunsets, stars and planets can be separated into its component colors to create spectra, as prisms do with sunlight, in order to obtain more information about a location's atmosphere. Although there are huge distances between Earth and some exoplanets, scientists have been developing techniques for collecting the spectra of these exoplanets.

So how exactly do they do it? When one of these planets passes in front of its host star, some of the star's light travels through the exoplanet's atmosphere. This subtle change can be measured and tell researchers a little bit more about the planet itself.

Now, scientists have exploited a similarity between exoplanet transits and sunsets seen by the Cassini spacecraft at Titan. Called solar occulations, these observations allow researchers to observe Titan as a transiting exoplanet without actually having to leave the solar system. This allowed them to see the effects of the moon's hazy atmosphere.

"Previously, it was unclear how hazes were affecting observations of transiting exoplanets," said Tyler Robinson, one of the researchers, in a news release. "So we turned to Titan, a hazy world in our own solar system that has been extensively studied by Cassini."

So what did they find? The researchers discovered that hazes high above some transiting exoplanets might strictly limit what their spectra can reveal to transit observers. In fact, the observations may only be able to glean information from the planet's upper atmosphere.

"People had dreamed up rules for how planets would behave when seen in transit, but Titan didn't get the memo," said Mark Marley, one of the researchers, in a news release. "It looks nothing like some of the previous suggestions, and it's because of the haze."

The findings reveal a little bit more about exoplanet atmosphere. This could be huge when finding out more about these planets during their transits.

You can learn more about Cassini here.