The number of exploding stars (supernovae) has significantly influenced the biodiversity of marine life over the last 500 million years.
This is the gist of a new study published in Ecology and Evolution by Henrik Svensmark, DTU space. Extensive studies of the fossil record have shown that the diversity of life forms has varied significantly over geological time, and a fundamental question of evolutionary biology is what processes are responsible for these variations.
The new study reveals a big surprise: the variable number of nearby exploding stars (supernovae) closely tracks changes in the biodiversity of marine genera (the taxonomic rank above species) over the past 500 million years. The agreement arises after normalizing the marine diversity curve due to changes in shallow marine areas along continental coasts.
Shallow sea shelves are relevant as most marine life lives in these areas, and changes in shelf areas open up new regions where species can evolve. Therefore, changes in available shallow areas influence biodiversity. “One possible explanation for the link between diversity and supernovae is that supernovae influence Earth’s climate,” says Henrik Svensmark, author of the paper and principal investigator at DTU Space. “A large number of supernovae leads to a cold climate with a large temperature difference between the equator and the polar regions. This results in stronger winds, the mixing of oceans and the transport of essential nutrients for life to surface waters. along the continental shelves.
The work concludes that supernovae are vital for primary bioproductivity by influencing nutrient transport. Gross primary bioproductivity provides energy to ecological systems, and speculation has suggested that changes in bioproductivity may influence biodiversity. The present results are in agreement with this hypothesis. “New evidence points to a connection between life on Earth and supernovae, mediated by the effect of cosmic rays on clouds and weather,” says Henrik Svensmark. 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 main source of ions that help form and grow the aerosols necessary for cloud formation.
Since clouds can regulate the solar energy reaching the Earth’s surface, the cosmic ray aerosol cloud influences the climate. Evidence shows substantial climate changes when cosmic ray intensity changes by several hundred percent over millions of years.