Understanding Exoplanet Atmospheres is Next Big Science

Understanding the composition of exoplanetary atmospheres is the next wave of study, as scientists work to analyze temperatures, clouds, and rainfall using better spectrographic instruments.

IMAGE: Swirling clouds highlight the atmosphere of a gas giant exoplanet in this artist’s concept. CREDIT: NASA/ESA/G. Bacon (STScI)

When I first came back to space science, I attended a meetup at NASA Ames Research Center to learn about the Kepler space telescope and its mission. Finding exoplanets was going to be a big deal in the upcoming years, and I was excited to be a small part of it. Now we’re at over 4000 discovered exoplanets and counting, to the point where exoplanet discovery announcements have to come with some sort of bonus reason as to why they’re important or interesting. Because “woo, look, another exoplanet” just doesn’t make headlines anymore.

So what’s next for the worlds of exoplanet science? One increasingly studied aspect is the atmospheres of those exoplanets. We’re getting to the point where we have instruments sensitive enough to gather data about atmospheric composition. Last week, we reported on finding various carbon isotopes in the atmosphere of a distant world. This isn’t a new science, though. In 2001, Hubble’s spectrographs found less sodium in a planet’s atmosphere than expected. Which led to researchers contemplating clouds as a reason they couldn’t see the sodium.

Huge banks of dark, hot clouds on a planet five times hotter than Earth, though, would make for some interesting weather. It’s unlikely that the droplets making up those clouds would be made of water. So now we have really neat hypotheses about clouds made of liquid sand, iron, rubies, diamonds. Clouds are difficult to study here on Earth, though. They’re simultaneously made of the microscopic and the huge — water droplets coming together to form a wide range of shapes and structures, covering more than two-thirds of the surface of Earth.

IMAGE: Artwork imagining the nightside of WASP-76 b, a hot Jupiter exoplanet with clouds of iron — and possibly even iron rain. CREDIT: ESO/M. Kornmesser

And our own solar system has its fair share of weird weather. Venus has sulfuric acid in its clouds. Jupiter has ammonia mushballs. Titan has methane and ethane rain. How do we…