Molten Planets and Early Atmospheres in the Laboratory

Funded by an ERC Starting Grant, MPS researcher Christian Renggli investigates a crucial phase of planetary evolution.

To the point:

• ERC Starting Grant: Over the next five years, the European Research Council will support the research group ELMO (Experimental Laboratory Magma Ocean) with 1.5 million Euros. 
• Magma oceans: At the beginning of their development, many planets are so hot that their rock melts. This is when the first atmospheres are formed.
• In the laboratory: Magma oceans and their atmospheres cannot yet be observed in space, but can only be simulated in the laboratory.
• New method: The research group uses an experimental setup that does not distort the interaction between molten rock and gases.

In the early days of our Solar System, huge oceans of red-hot magma covered each of the four inner planets Mercury, Venus, Earth, and Mars. The heat required to melt the rock came from the decay of radioactive elements or from violent impacts. Gases escaped from the magma, creating the first atmospheres. Such magma oceans and their pristine atmospheres are likely to still exist today on young, still hot exoplanets outside our Solar System. The scope of Christian Renggli's new research group at the Max Planck Institute for Solar System Research (MPS) is to better understand this phase of planetary evolution. The project will help to answer the question why, after cooling down, Earth developed into a life-friendly planet, while other planets lack the necessary conditions for the emergence of life.

Since there is no direct access to magma oceans and their atmospheres, the search for answers to this question leads the researchers of the group ELMO (Experimental Laboratory Magma Ocean) into the laboratory. In the case of our Solar System, billions of years separate us from this early state. Although rock from this period has been preserved on some celestial bodies, the gas envelopes that formed at that time have since evolved dramatically or even disappeared. In the case of distant, still hot exoplanets, space, not time is the problem. From a distance of thousands of light-years, telescopes in space or on Earth can provide clues about the composition of planetary atmospheres. However, the list of ingredients of their magma oceans remains a mystery.

Just a few milligrams of molten rock suffice to  recreate  a planetary magma ocean in the laboratory. The artificial magma consists primarily of silicate rocks, which make up the majority of the crust and mantle of the inner planets in our Solar System. Other ingredients such as water and sulfur are added to the experiment in a controlled manner. The artificial rock is then heated to up to 2000 degrees Celsius in a closed chamber. Gases evaporate and are partially dissolved again gradually establishing an equilibrium between the magma and the gas layer   just as in the early Solar System. Unlike in conventional experiments, the G ttingen researchers for the first time extract only a tiny stream of gas from their experimental setup and analyze its exact composition in a quadrupole mass spectrometer. This ensures that the equilibrium between magma and gas is not disturbed or distorted.

Observational data from current space missions such as the ESA s space probes BepiColombo and PLATO, as well as the James Webb Space Telescope, will supplement the laboratory data and embed it in the larger context of the entire formation and evolution of planets.

About the researcher and ERC Starting Grants

Dr. Christian Renggli studied at the University of Bern in Switzerland and at Ludwig Maximilian University in Munich, and received his doctorate from the Research School for Earth Sciences at the Australian National University. After five years at the University of M nster, Christian Renggli began researching at the MPS two years ago. In 2023, he received the Pauli Niggli Medal from the Swiss Geological Society for his research findings on volcanic eruptions on Earth, Mercury, and the Moon. Christian Renggli is involved in ESA's BepiColombo mission to Mercury and is a member of the scientific consortium for ESA's PLATO mission, which will search for and characterize exoplanets starting in early 2027.

With its coveted ERC Starting Grants, the European Research Council (ERC) supports young scientists who are still at the beginning of their careers. The funding enables them to pursue an ambitious research project within the framework of an own research group. For the current funding period, the European Research Council received more than 3,900 applications. 478 of them were selected for funding.

With the research group ELMO, the MPS receives its seventh ERC Starting Grant. In addition to ELMO, two other projects are currently being funded; the other projects have already been completed.