In the time since I was born, we have gone from knowing about zero planets orbiting other stars to a catalog of over 4,000 strange new worlds. Yet much remains to be discovered about these planets' exact natures. This is especially true of small, terrestrial worlds—the ones that may, or may not, resemble our home. What are their environments like? Could any of them harbor life? If so, how might we detect it?

     My current research investigates the chemistry of exoplanetary atmospheres around other types of stars. Imagine taking Venus and throwing it around a cool, dim, red star—the most common type of star in the galaxy. (One such red dwarf is TRAPPIST-1, which is known to host seven roughly Earth-sized planets—some of which orbit within the star's habitable zone.) How does a complex web of chemical reactions change in response to a different distribution of starlight?

I love stories, and science tells us the most incredible story of all. Not only are we children of our parents, but of the Earth and the universe as well. How did we become the magnificent biological contraptions that we are? Which forces first culminated in the powers of metabolism and reproduction? What was written on our first page? And are there similar stories all across the cosmos? There is still so much we don't know about our own living existence, especially when it comes to our enigmatic birth.

    I modeled the production of nitrogen oxides on early Earth, which is a potentially crucial ingredient for the theory of the emergence of life at submarine alkaline hydrothermal vents. With my colleague Dr. Stuart Bartlett, I published a perspective on emergence-of-life theories, introducing lyfe, a new definition of life based on four fundamental processes that characterize the living state.

Our next-door neighbor is a conundrum. Ancient landforms and minerals indicate that Mars was once much wetter than the bone-dry desert that it is today. But climate models of ancient Mars fail to attain high enough temperatures for liquid water to flow at a time when the Sun was only three-quarters as bright. The answer to this paradox may be an abundance of hydrogen and methane in Mars's early atmosphere.

     With Danica Adams and others, I helped model the production of nitrogen-bearing compounds—including nitrogen oxides and hydrogen cyanide—on a wet, warm early Mars that featured substantial atmospheric hydrogen and methane. These chemicals may have contributed key nutrients for the emergence and sustainment of life on the Red Planet early in its history. With Lucas Fifer, I am working on quantifying the habitability of ancient Mars.

In July of 2015, the New Horizons spacecraft unveiled a stunning sight: Pluto. This frozen world exhibits extraordinary complexity, from its diverse terrain to the varied hues painting its surface to its unexpected atmospheric structure. Such features point to ongoing geological activity. Pluto may be cold and tiny, but it is certainly not boring.

     Using an adapted photochemical model for Titan (see below) and data from New Horizons, my colleagues and I sought to understand how atmospheric physics and chemistry behaves under Pluto's unprecedentedly low temperatures and pressures. Dr. Peter Gao and I published a pair of papers, one on Pluto's photochemistry and one on the microphysics of Pluto's fractal aggregate haze.