Exoplanets and Planetary Science: Two Different Worlds?

Alexandra Lehtmets, Peter Mc Ardle, Prasanna Deshapriya, Prateek Tripathi and Hans Huybrighs on behalf of the Europlanet Early Careers (EPEC) Future Research Working Group interview Europlanet Early Career Medal Winner, Tim Lichtenberg.

Which role does interdisciplinarity play in your career?

*Tim Lichtenberg. Credit: T Lichtenberg.*

I consider my own work to be highly interdisciplinary, even transdisciplinary. My academic journey has taken me from a background in classical physics to astrophysics (BSc/MSc University of Göttingen) and then to geophysics (PhD at ETH Zurich). After that I was a postdoctoral researcher studying planetary & atmospheric formation at the University of Oxford. I am currently an assistant professor at the Kapteyn Astronomical Institute of the University of Groningen in the Netherlands.

I focus on developing our understanding of how the initially uninhabitable conditions of a planet (e.g. Earth’s magma ocean phase), change to become more habitable (e.g. Earth today). To do this, my work primarily addresses the interface between the interiors and atmospheres of planets. By observing exoplanets, we can fill the gaps in our current knowledge of the formation process, which is primarily based on our own Solar System. We now have detected so many exoplanets that we can sample all the stages of planetary formation and test our models.

Despite the emphasis from major funding agencies, it remains difficult to secure funding for interdisciplinary research because such proposals often face more criticism. Crossing disciplinary boundaries increases the potential for conflict. In reality, few funding bodies are truly dedicated to supporting interdisciplinary science. That’s why foundations like the Branco Weiss Fellowship are so valuable—they actively encourage interdisciplinary projects and offer researchers the freedom to pursue their questions without strict disciplinary constraints. This flexibility has been key in shaping the research group I’m building today.

Importantly, some of these distant worlds might reflect earlier phases of planetary evolution in the Solar System that are no longer observable.
Tim Lichtenberg

How are recent advances in exoplanetary science influencing planetary science?

Exoplanets are revealing just how much broader planetary science can be and challenge our assumptions about planetary formation and evolution. Many exoplanets exist in states unlike anything observed locally. Their diversity in composition, climate, and chemistry forces us to re-evaluate models originally built to describe only our own Solar System planets.

The James Webb Space Telescope (JWST) is a major breakthrough. For the first time, we can obtain high-quality spectra from medium-sized exoplanets, particularly sub-Neptunes. These are planets larger than Earth but smaller than Neptune, a type missing from our own system. Initial findings suggest that some of these worlds may be rich in water, while others could be extreme magma ocean planets with entirely molten interiors. These unusual structures reveal different physics and chemistry than we see on familiar terrestrial planets like Earth, Mars, or Venus.

Importantly, some of these distant worlds might reflect earlier phases of planetary evolution in the Solar System that are no longer observable. By studying them, we can piece together how early atmospheres formed and evolved.

Exoplanet science bridges multiple disciplines. How do you integrate techniques ranging from spectroscopy, atmospheric modeling to the analysis of returned samples, and other areas into your work?

I don’t think in disciplinary terms, but in terms of the feature being investigated – we are all studying nature. There is a strong synergy between solar system science, e.g. sample return missions, and exoplanetary science. We are trying to answer similar questions, but with different datasets. One method on its own will not answer all the questions, so these approaches are complementary. However, we do need to work closer together and not be siloed, there are lots of opportunities for us to learn from each other.

I have been trying to grow my usage and expertise of methods and discipline, piece by piece, over time. Going from astrophysics, to geophysics to atmospheric science. From a personal perspective, you try to understand piece by piece how it all fits together. However, we don’t work in isolation, we must rely on collaborators, and others with other expertise. This interplay is very important.

Chronology of geophysical and geochemical processes that affect the interior dynamics, structure, and climate of rocky planets. Planet size is normalized to current growth stage, starting from accretion in the disk (planetesimal stage), post-disk (giant impact phase), planet solidification and atmosphere formation (magma ocean crystallisation), to the long-term evolution of interior and climate (secular geodynamic evolution). Credit: Lichtenberg et al.

What are the biggest open questions about the conditions that led to life on early Earth that you might be able to answer with your research ?

When it comes to the origin of life on Earth, we still know remarkably little about the surface state and geochemistry of the Hadean and early Archean eons. Geochemical clues—like zircon crystals—offer partial insights, but their interpretation remains highly debated. We don’t fully understand how the Earth transitioned from a molten magma ocean to a solid planet, nor how early surface environments and atmospheric chemistry evolved to support life. That’s where exoplanet science becomes invaluable. These exo-worlds may not mirror Earth exactly, but studying how they evolve from molten beginnings to potentially habitable environments can reveal fundamental processes that likely played a role in life’s emergence here.

Every discipline has a critical angle on this big question. In geophysics we need to explore how volcanic activity functions under non-Earth-like conditions, especially in chemically reduced environments—something we currently have almost no data for. It may seem speculative, but this kind of parameter exploration is crucial for interpreting what we observe astronomically. From the stellar side, better understanding of host stars remains key. And from a climate science perspective, while our models are becoming more generalized and capable of handling a variety of planetary scenarios, we still struggle with validation—we can run the models but knowing if they’re right is a major challenge.

Knowing how little we truly understand leaves space for creativity and progress.
Tim Lichtenberg

What advice would you give early career researchers interested in becoming part of the future of exoplanet science, including the LIFE mission?

We actually understand very little about how terrestrial planet evolution works—our knowledge of Earth’s history is still quite limited, and when it comes to extrasolar planets, it’s closer to next to nothing. Knowing how little we truly understand leaves space for creativity and progress, which I think is encouraging for any early-career scientist interested in these questions.

I think what we urgently need is a better understanding of how all these processes—physics, chemistry, and interdisciplinary expertise—work together on a planetary scale. Habitability is a diffuse target, so starting your career by focusing on one sub-problem, even if it’s seemingly not at the center, can be valuable. For example, geological aspects play a crucial role in the long-term evolution of terrestrial planets and can serve as a strong foundation to build outward from.

In the context of future missions—like the LIFE space mission concept and others—there’s a clear need to build on strong interdisciplinary knowledge. Working on core aspects and engaging with others interested in similar questions can help uncover opportunities for collaboration and enable truly interdisciplinary projects.

*Rendering of the LIFE mission, a space-based nulling interferometer concept that aims to measure the emission spectrum of terrestrial exoplanets. Credit: LIFE Initiative.*

How do you think public engagement and outreach in exoplanet science can inspire early-career researchers and motivate the next generation to pursue breakthroughs in this field?

I do think outreach and science communication are critically important. I became a researcher because, as a teenager, I read a lot of popular science books and realized how fascinating science is—not just the dry, sometimes uninspiring version we often encounter in school. So yes, inspiring the next generation of scientists through communication is essential.

That said—and maybe I’m a little biased—I don’t think exoplanets need much advertisement. The idea that there are countless worlds out there, each with different climates, surfaces, and perhaps even biological life, is so unbelievably fascinating that it speaks for itself.

I do think the work we are all doing is giving us something to work for, something bigger than us.
Tim Lichtenberg

Do you have any advice about doing research in today’s chaotic world?

Sometimes I have the impression that everything goes to pieces in the current political climate and that people are not sure if they should put effort into something. I do think the work we are all doing is giving us something to work for, something bigger than us. Something inspirational, something important, the big picture. This can help you enrich your life and focus on something else to think about and contribute towards.

A short version of this article is in Issue 8 of the Europlanet Magazine.

More interviews from the Future Research Working Group.