About Me

I’m Robb, a PhD student at the Institute of Astronomy, University of Cambridge. My research focuses on the atmospheres and interiors of Sub-Neptunes: planets between the size of Earth and Neptune. They are the most common type of planet in the galaxy, but there is still so much we don't know about them. What are they made of? How did they form? Could they support life? I use coupled interior-atmosphere models to simulate their evolution and their potential for hosting life.

Research

Magma Oceans on Sub-Neptunes

My current work focusses on the thermal evolution of magma oceans on Sub-Neptunes. Most of the rocky planets in the solar system, such as Earth, Mars and Venus, began in a fully molten state. Over time, their surfaces solidified, and they continued to evolve into the worlds we observe today. For Sub-Neptune sized planets, the evolution of magma oceans may differ significantly from that of the Solar System planets because of their massive, hydrogen-dominated atmospheres. Using the PROTEUS modelling framework, we investigate the factors that govern magma ocean evolution on sub-Neptunes, and assess whether some may host permanent magma oceans that never solidify.

Ozone on Venus

My previous research has focused on ozone in the atmospheres of Venus-like planets. The presence of an ozone layer in Venus' mesosphere is a puzzle for planetary scientists: its origin remains unknown. If a similar ozone layer were found on other Venus-like worlds, it could complicate the use of ozone as a marker for identifying habitable Earth-like planets. I’ve been using atmospheric models to investigate the source of Venus' ozone and explore whether it might appear on other planets with similar conditions.

Selected Publications

  • Calder, R., Shorttle, O., Jordan, S., Rimmer, P., & Constantinou, T. (2025). Abiotic ozone in the observable atmospheres of Venus and Venus-like exoplanets. Monthly Notices of the Royal Astronomical Society, 540(3), 2432-2450. (ADS Link).
  • Helling, C., Samra, D., Lewis, D., Calder, R., Hirst, G., Woitke, P., ... & Chubb, K. L. (2023). Exoplanet weather and climate regimes with clouds and thermal ionospheres-A model grid study in support of large-scale observational campaigns. Astronomy & Astrophysics, 671, A122 (ADS link).

CV

Contact

Address

Institute of Astronomy
Madingley Rd, Cambridge
CB3 0HA

E-mail

rdc49@cam.ac.uk