The extraterrestrial processes responsible for influencing the diversity of life forms are usually invisible to the human eye. The Milky Way is where large stars explode, leading to supernova remnants whose shock fronts accelerate cosmic ray particles to high energies. Cosmic rays find their way to the solar system, where some collide with the atmosphere producing cascades of secondary particles which ionize the atmosphere. Ions influence the formation of clouds which ultimately affect climate. Therefore, changes in supernova activity change climate, which is responsible for mixing and transporting life’s essential nutrients to the ecosystems. Credit: Henrik Svensmark, DTU Space
A new study published in Ecology and Evolution by Henrik Svensmark of DTU Space has shown that the explosion of stars, also known as supernovae, has greatly impacted the diversity of marine life over the past 500 million years.
The fossil record has been extensively studied, revealing significant variations in the diversity of life forms throughout geological history. A fundamental question in evolutionary biology is identifying the processes responsible for these fluctuations.
The new research uncovers a surprising finding: the fluctuation in the number of nearby supernovae closely corresponds to changes in biodiversity of marine genera over the last 500 million years. This correlation becomes apparent when the marine diversity curve is adjusted to account for changes in shallow coastal marine regions, which are significant as they provide habitat for most marine life and offer new opportunities for evolution as they expand or shrink. Thus, alterations in available shallow marine regions play a role in shaping biodiversity.
“A possible explanation for the supernova-diversity link is that supernovae influence Earth’s climate,” says Henrik Svensmark, author of the paper and senior researcher at DTU Space.
“A high number of supernovae leads to a cold climate with a large temperature difference between the equator and polar regions. This results in stronger winds, ocean mixing, and transportation of life-essential nutrients to the surface waters along the continental shelves.
Variations in relative supernova history (black curve) compared with genera-level diversity curves normalized with the area of shallow marine margins (shallow areas along the coasts).
The brown and light green curves are major marine animals’ genera-level diversity.
The orange is marine invertebrate genera-level diversity.
Finally, the dark green curve is all marine animals’ genera-level diversity.
Abbreviations for geological periods are Cm Cambrian, O Ordovician, S Silurian, D Devonian, C Carboniferous, P Permian, Tr Triassic, J Jurassic, K Cretaceous, Pg Palaeogene, Ng Neogene. Credit: Henrik Svensmark, DTU Space
The paper concludes that supernovae are vital for primary bioproductivity by influencing the transport of nutrients. Gross primary bioproductivity provides energy to the ecological systems, and speculations have suggested that changes in bioproductivity may influence biodiversity. The present results are in agreement with this hypothesis.
“The new evidence points to a connection between life on Earth and supernovae, mediated by the effect of cosmic rays on clouds and climate,” says Henrik Svensmark.
Supernovae and Climate
When heavy stars explode, they produce cosmic rays, which are elementary particles with enormous energies. Cosmic rays travel to our solar system, where some end their journey by colliding with Earth’s atmosphere. Previous studies by Henrik Svensmark and colleagues referenced below show that they become the primary source of ions help form and grow aerosols required in cloud formation.
Since clouds can regulate the solar energy reaching Earth’s surface, the cosmic-ray-aerosol-cloud influences climate. Evidence shows substantial climate shifts when the intensity of cosmic rays changes by several hundred percent over millions of years.
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