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Department of Earth Sciences

Artist's impression of planets and their orbits

How can thinking and expertise from a discipline forged in Earth’s 4.6 billion-year-old history inform the search for life beyond our solar system?

This month’s edition of Elements Magazine International, titled ‘Geoscience Beyond the Solar System’, and co-edited by Cambridge University’s Dr Oliver Shorttle, explores what the field of Exoplanetary Sciences can learn from its older, Earth-loving discipline – geology -- and how the growth of both communities calls for collaborative problem solving.

Dr Oliver Shorttle collaborated on the special issue with Dr Natalie Hinkel and Dr Cayman Unterborn at the Southwest Research Institute.

Introducing the edition, Shorttle argues that, only by bridging expertise between Earth and Exoplanetary Sciences, can fundamental science conundrums be solved, like the age-old mystery of what makes our home planet habitable, and whether alien worlds might hold the right recipe for life.

“Some of the most profound questions in both fields can only be answered by both disciplines working together. If we can look to other worlds, we can finally break the n=1 challenge: we’re no longer limited to Earth being our only case study,” said Shorttle, who is jointly based at Cambridge’s Department of Earth Sciences and Institute of Astronomy.

According to Shorttle, unravelling how exoplanets work needs help from Earth Scientists, who can draw on their expertise and upscale the experiments based on Earth to planets beyond our solar system.

The call-to-action comes as the field of Exoplanetary Sciences continues to develop at lightning speed, with an ever-expanding dataset from our skies leading to the continual discovery of new planets beyond our solar system.

Now numbering in their thousands, these exoplanets are strikingly diverse: some Earth-sized, others bathed in permanent day or night or even covered by nightmarish magma oceans. These differences aside, the burning question for Exoplanetary Scientists is, are any exoplanets Earth-like? That question, something of a holy grail for the science community, is more difficult to answer than first seems. On discovery, the only information we have on exoplanets is limited to either their size or mass (or more rarely both). To decide whether telescope time should be dedicated to making more detailed observations, it is critical to use our understanding of geological processes, honed from the study of Earth, to predict what these alien worlds might be like. 

“The Exoplanetary Sciences is undergoing a sea-change – we’re moving away from simply discovering new planets to characterizing their composition, formation and evolution. Ultimately looking for the right ingredients for life,” said Shorttle.

“We may be just a decade or two away from finding life elsewhere in our galaxy” said Dr Paul Rimmer, who co-authored one of the articles inside the edition and is based at the Department of Earth Sciences and the Cavendish Laboratory at the University of Cambridge, and the MRC Laboratory of Molecular Biology in Cambridge. “That is immensely exciting in itself, but if we do find life, that life may tell us more about ourselves and how life on Earth might have first started and evolved.”

Such collaborations could also help Earth Scientists get to the root of how our home planet works, “It’s a two-way street: we stand to learn more about Earth and answer conundrums like: when did plate tectonics begin – how ubiquitous is this process, how did our planet develop and maintain a habitable environment?” said Shorttle.

  These conundrums include the classic hypothesis for regulating Earth’s climate. Since the mid-20th Century, scientists have worked on the basis that CO2 from our atmosphere is sucked down into Earth’s interior by the breakdown of rocks, then cycled back up to the surface by volcanoes. But our knowledge of the process is still flawed and continually being revised. Shorttle argues that the workings of this so-called silicate weathering cycle may be revealed by looking beyond our solar system, in observations of exoplanet’s atmospheres.

“It’s time to step back and look at the big overarching questions governing both of our disciplines – the questions we ask as Earth Scientists, like how our planet formed and works, are fundamentally the same as those asked by Exoplanetary Scientists. It is time to expand our horizons and join forces,” said Shorttle.

Earlier this year, the University launched its ambitious ‘Cambridge Initiative for Planetary Science and Life in the Universe’. As part of the program, Earth Scientists will work together with physicists, chemists, biologists and mathematicians in search of the processes that could make other planets suitable for life.


The special issue of Elements Magazine International will be available on 18th October and can be accessed online here.