Supernova radiation may have triggered species diversification on Earth: Study
A recent study led by Caitlyn Nojiri from UC Santa Cruz and published in the Astrophysical Journal Letters, points to a mind-blowing possibility: a supernova explosion nearby might have really shaken things up for life on Earth. The research zoomed in on two deposits of the iron isotope Fe60 found in seafloor sediments. Scientists think these deposits are leftover bits from supernovae that blew up around two to three million years ago and five to six million years ago, respectively.
Supernovae and their impact on Earth's radiation levels
The research team looked into how much energy from these supernovae made its way to Earth and how it might have affected life here. They pointed out "life on Earth is constantly evolving under continuous exposure to ionizing radiation from both terrestrial and cosmic origin." While terrestrial radiation slowly fades over billions of years, cosmic radiation fluctuates as our solar system travels through the galaxy. The study hints that supernova activity nearby could really ramp up Earth's surface radiation levels.
Tracing the origins of iron isotope deposits
The researchers believe that the younger Fe60 deposit, dating back two to three million years, is a direct result of a supernova explosion. On the other hand, they think the older deposit, which is from five to six million years ago, came about when Earth cruised through a bubble. This "bubble" is basically a region of hot gas in the interstellar medium, formed by strong winds of OB stars—those massive, hot, and short-lived stars that often hang out in groups.
Earth's journey through the Local Bubble
Our solar system is hanging out inside one of these bubbles, called the Local Bubble. This bubble's about 1,000 light-years wide and was formed millions of years ago. The researchers think Earth slid into this Local Bubble around five to six million years back, matching up with when older Fe60 deposit happened. They also believe several supernovae had a hand in making this bubble, with at least nine of them going off inside it in the last six million years.
Supernova radiation and its potential effects on life
The researchers looked into how much radiation multiple supernovae in the Local Bubble might have blasted our way. They suggest that this radiation could've been intense enough to cause double-strand breaks in DNA, potentially leading to chromosomal changes and even cell death. They also pointed out that such DNA damage "can potentially lead to mutations and jump in the diversification of species." Now, that's got us wondering: could supernova radiation have influenced the biodiversity we see on Earth today?
