A star’s spectacular death in the constellation Taurus was observed on Earth as the supernova of … [+]
The number of exploding stars (supernovae) has significantly influenced marine life’s biodiversity during the last 500 million years, so the conclusion of a study published by Dr. Henrik Svensmark, professor at the Technical University of Denmark.
The fossil record have shows that the diversity of life forms has varied significantly over geological time and a fundamental question of evolutionary biology is which processes are responsible for these variations.
The new study reveals a major surprise: The varying number of nearby exploding stars closely follows changes in marine genera biodiversity during the last 500 million years. To make this connection, Svensmark compared the number of known fossil genera, the levels of cosmic rays hitting Earth over time as recorded by traces of radioactive elements preserved in marine sediments, and the distribution and size of shelf areas surrounding the continents.
Shallow marine shelves are relevant since most marine life lives in these areas, and changes in shelf areas open new regions where species can evolve. Therefore, changes in available shallow areas influence biodiversity.
“A possible explanation for the supernova-diversity link is that supernovae influence Earth’s climate,” explains Svensmark.
When stars explode, they produce cosmic rays, which are elementary particles with enormous energies. Some end their journey by colliding with atoms in Earth’s atmosphere. The ionized atoms attract water vapor, acting as seeds to form droplets of water suspended in the air. If enough droplets join together, they will form fog and clouds. This way, the amount of cosmic rays hitting Earth can influence the cloud cover in Earth’s atmosphere, and more clouds means less sunlight reaching Earth’s surface, cooling the planet. Previous studies by Svensmark and colleagues shows substantial climate shifts when the intensity of cosmic rays changed over millions of years.
The new paper concludes that supernovae influence life on Earth by changing the climate and how nutrients are distributed by marine currents over the planet.
“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,” Svensmark concludes.
But there is a problem with this hypothesis.
So far, the formation of cloud seeds by ionizing energy was only observed under laboratory conditions. It also needs to be clarified how or even if cosmic rays influence other factors for cloud formation. As a result, many climatologists consider the effects of cosmic rays on Earth’s climate negligible.
The study “A persistent influence of supernovae on biodiversity over the Phanerozoic” was published in the journal Ecology and Evolution (2023). Material provided by the Technical University of Denmark.
