Over the past 500 million years, the frequency of exploding stars, or supernovae, has had a tremendous impact on the variety of marine life. This is the primary premise of a recent study by Henrik Svensmark, of DTU space, that was published in the journal Ecology and Evolution.
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. Image Credit: Henrik: Svensmark, DTU Space
Numerous analyses of the fossil record have revealed that the variety of life has changed dramatically over time. Which processes are responsible for these changes is an essential question in evolutionary biology.
The latest research indicates a major surprise. Throughout the past 500 million years, changes in the diversity of marine genera (the taxonomic rank above species) have closely followed changes in the number of nearby exploding stars, or supernovae.
After adjusting for changes in shallow marine areas around continental coasts, an agreement is seen in the marine diversity curve. Since the majority of marine life resides on shallow marine shelves, these regions are important since changes to these shelves create new habitats for species to develop. Thus, changes in the shallow areas that are available have an impact on biodiversity.
A possible explanation for the supernova-diversity link is that supernovae influence Earth's climate. 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.
Henrik Svensmark, Study Author and Senior Researcher, Danish National Space Institute
The study concludes that supernovae have an important role in primary bioproductivity by affecting nutrient transfers. The ecological systems are powered by gross primary bioproductivity, and theories have proposed that variations in bioproductivity may have an impact on biodiversity. The current findings are consistent with this theory.
Svensmark added, “The new evidence points to a connection between life on Earth and supernovae, mediated by the effect of cosmic rays on clouds and climate.”
Supernovae and Climate
Cosmic rays are elementary particles with extremely high energy that are created when massive stars explode. When cosmic rays reach the solar system, some of them come to an end by slamming against the atmosphere of Earth.
They are the main source of ions that help generate and increase the aerosols needed for cloud formation, according to earlier studies by Henrik Svensmark and colleagues that are cited below.
Since clouds have the ability to control the amount of solar radiation that reaches the Earth’s surface, they have an impact on climate. There is evidence for significant climatic changes when cosmic ray strength varies by several hundred percent over millions of years.
Journal Reference
- Svensmark, H., (2023) A persistent influence of supernovae on biodiversity over the Phanerozoic. Ecology and Evolution. doi:10.1002/ece3.9898
- Svensmark, H., (2021) Supernova Rates and Burial of Organic Matter. Geophysical Research Letters. doi:10.1029/2021GL096376
- Svensmark, H., et al. (1997) Variation of Cosmic Ray Flux and Global Cloud Coverage -A missing Link in Solar-Climate Relationships. Journal of Atmospheric and Terrestrial Physics. doi:10.1016/S1364-6826(97)00001-1
- Shaviv, N. J., et al. (2023) The phanerozoic climate. Annals New York Academy Sciences. doi:10.1111/nyas.14920
- Svensmark, H. (2012). Evidence of nearby supernovae affecting life on Earth. Monthly Notices of the Royal Astronomical Society. doi10.1111/j.1365-2966.2012.20953.x