In this episode, we are in conversation with Dr. Craig Walton, a planetary scientist based at ETH Zürich and the University of Cambridge. Craig’s work spans the origins, evolution, and distribution of life in the Universe.

In this podcast, we chat about cosmic dust, the origins of life on Earth, and phosphorus—a key element for life, known as the ‘bringer of the light of day’, and its more fiendish nickname, “The Devil’s Element”. In a paper published in Nature Astronomy in February 2024, Craig and his colleagues note that life on Earth probably originated from “reservoirs of bio-essential elements” such as phosphorus, sulfur, nitrogen, and carbon. But our earth rocks are relatively poor in reactive and soluble forms of these elements. So where did they come from? Apart from meteorites and asteroids, they could have also found their way to earth through cosmic dust, mineral grain aggregates of less than 3 mm derived from asteroids and comets. And glaciers provide settings capable of both locally concentrating cosmic dust and initiating closed-system
aqueous prebiotic chemistry in cryoconite holes, self-sustaining puddles or lakes.

In a more poetic turn, we talked about meteorites, which has been termed by Elizabeth Grosz
as the ultimate outsider, a cosmological imponderable that might burst through the perceived
limits of the known. Craig noted that these materials speak at a deeper level about where we
come from and how we should live. Potentially, all life derives from these cosmic gifts. We
are really made of stardust. Everything about meteorites and their eviscerated metallurgic
intensity speaks to their incredible durability. We then moved on to Craig’s PhD thesis on phosphorus, the backbone of DNA and our metabolism. It cycles through ecosystems in a mostly closed loop as organisms live, die and decay. This remarkable element, crucial for global food production, allows our civilization to flourish. However, with its overuse, we now face the dangers of fertilizer run-off such as algal blooms which can lead to ocean anoxic events which have been correlated with mass extinctions. For four and a half billion years, life has recycled minerals and resources, but we humans take them for granted. We churn through these resources, dump them in the oceans and move on. It can’t end well.

Outside of research, Craig writes science fiction as well as science communication articles on
a wide range of topics. If you want to hear more from Craig about all of the above, you can follow him on Twitter/X @lithologuy for updates.

The Subverse is the podcast of Dark ‘n’ Light, a digital space that chronicles the times we live in and reimagining futures with a focus on science, nature, social justice and culture. Follow us on social media @darknlightzine for episode details and show notes.