Extreme climates

The atmosphere controls the environment of a planet. We sit on a wonderful world, the third planet from our Sun, under an atmosphere that is 78% nitrogen—a stable, inert gas. Most of the rest is oxygen, which is essential for land animals and plants to breathe. In contrast, Mars is smaller and less massive, meaning its gravitational pull was too weak to hold onto a thick atmosphere. Most of its very thin atmospheric layer is carbon dioxide, resulting in a surface environment very different from ours.

Hydrogen and helium are the two most abundant elements in the universe, created just after the Big Bang. Gas giants can hold onto these light materials because of their massive gravitational pull. Interestingly, the atmosphere we breathe today is actually the fourth generation of Earth's atmosphere. Our first atmosphere was hydrogen and helium from the solar nebula, but the Earth's gravity wasn't strong enough to keep it; those molecules moved faster than our planet's escape velocity. We had to create a secondary atmosphere that evolved through biology over time. The air we exist in now is only about half a billion years old.

A planet's atmosphere is the entire system of gases, while its climate is the long-term weather conditions within that system. Climate is defined by factors like a planet's rotation rate, radiation from its star, and gas composition. Any small change in the atmosphere can affect local weather patterns and the general structure of the global system. These systems are all linked and highly sensitive to small changes.

I observe extreme climates where planets are incredibly hot, with temperature differences of hundreds of degrees between their sides. These massive differences can create clouds on only one side, rains of glass, and supersonic winds traveling at thousands of miles per hour. However, even a tiny difference can have a huge impact. On Earth, the amount of carbon dioxide has increased by only about 40 parts per million in the last 50 years, yet that small change impacts our overall temperature.

This tiny increase in carbon dioxide is what we call global warming or climate change. Carbon dioxide is exceptionally good at absorbing the infrared heat our planet gives off, making us more efficient at retaining that heat. As the average temperature shifts, it increases climate extremes, making some places incredibly hot or cold and expanding deserts. Even the location of clouds is key; moving them from the equator to elsewhere changes the entire climate system. We can see these effects happening here on Earth in real time.

Studying exoplanets allows us to ask how planetary systems form and how life emerges. This requires a fundamental understanding of how stars make planets and how those planets are protected during formation. We investigate whether the specific configuration of our solar system—small rocky planets close to the star and giants further out—is needed for life. By piecing together this massive jigsaw puzzle of planets and stars, we can eventually place our world in the galaxy and ask if there is anything like us out there.

Deciphering what these distant worlds are like reveals the wonder and majesty of science. We can learn so much about a planet just by looking at the light it emits. Science is far more creative than people realize; we have to look at these environments and work out what we are missing. I want people to feel the wonder of answering profound questions from something as simple as a beam of light.