The science of air now forecasts storms on Jupiter and distant exoplanets
Atmospheric science began with weather balloons and ground stations, but its reach now includes a storm on Jupiter bigger than Earth, planet-wide dust storms on Mars and a gas giant around another star with a spot perhaps twice that size. Every planet orbiting our Sun, it turns out, holds on to some air.
The field splits by timescale and altitude. Meteorology, which folds in atmospheric chemistry and physics, focuses on weather lasting up to a few weeks. Climatology looks at how often such systems recur and how the averages drift over years to millennia, borrowing from oceanography, geology, biology and astronomy. Aeronomy studies the thin air above the stratopause, where molecules split apart and become ionised. Léon Teisserenc de Bort and Richard Assmann were among its early pioneers, and today's toolkit ranges from radiosondes and radar to lasers and satellites such as CALIPSO, a NASA and French space agency mission that tracks how clouds and airborne particles shape weather and climate.
Atmospheric chemistry matters most because air interacts with living things. Human activity has altered its make-up in ways that harm health, crops and ecosystems, and chemists have tackled acid rain, photochemical smog and greenhouse warming. Atmospheric nitrous oxide, for instance, rose by about a quarter between 1750 and 2022. Dynamicists, meanwhile, try to explain thunderstorms, tornadoes, jet streams and global circulation from the basic laws of physics, with better forecasts as the payoff.
Looking outward, gravity decides who keeps an atmosphere. Massive gas giants retain light hydrogen and helium; smaller worlds let them escape. The solar wind has stripped much of Mercury's air away, and among moons only Titan holds a dense one, with Triton managing a thin layer and our Moon a mere trace. Earth stands apart for its free oxygen, put there by life itself.
Some exoplanets called hot Jupiters are shedding their atmospheres under stellar radiation, trailing gas rather like comet tails. On HD 189733 b, though, day and night sides show similar temperatures, a sign its winds spread the star's heat around the globe.
Source: Atmospheric science
