Unusual Link Between Cosmic Rays and Viruses on Earth

Over two million years ago, an intriguing occurrence took place concerning the viruses that infect fish in Lake Tanganyika, located in East Africa. These viruses diversified at an alarming rate, showing increased mutation rates that have puzzled scientists.

Lake Tanganyika is the deepest freshwater lake in Africa and is situated within the East African Rift, surrounded by steep highlands that keep it isolated from surrounding areas. This massive lake spans more than 400 miles (about 645 kilometers) and contains a large amount of the world’s freshwater resources.

Researchers have proposed a connection between the rapid diversification of fish viruses and rising levels of cosmic radiation during the same time frame. Cosmic rays are high-energy particles that travel through space almost at the speed of light. They originate from various sources, including supernovae (explosions of stars), the Sun, and even from mysterious sources located beyond our galaxy. When these particles collide with the Earth’s atmosphere, they produce a flurry of secondary particles that can sometimes reach the Earth’s surface.

Some cosmic rays possess such high energy that they can interfere with electronics, disrupt satellite communications, and slightly increase radiation exposure for astronauts and individuals on high-altitude flights. While researchers continue to uncover the mysteries of cosmic rays, it is certain that they are integral to the universe’s energetic landscape.

Cosmic rays, despite their dramatic-sounding name, are a natural phenomenon on Earth. The planet’s magnetic field and atmosphere serve as a protective barrier that blocks the majority of cosmic rays before they can impact us. Nonetheless, these rays do impact Earth’s environment; some studies suggest they might even play a role in cloud formation, potentially influencing weather and climate patterns.

In earlier investigations, scientists uncovered radioactive iron within deep-sea sediments, providing evidence of a nearby supernova event occurring around 2.5 million years ago. This stellar explosion likely emitted intense cosmic radiation that collided with the Earth’s surface for an estimated duration of about 100,000 years.

“The connection between such distant cosmic events and our planet’s life is exciting to explore,” said Caitlyn Nojiri, a lead author from UC Santa Cruz. Past research has shown that cosmic radiation can damage DNA, which might lead to changes in genetic material and affect how organisms evolve.

Nojiri and her team aimed to find out whether cosmic radiation might have influenced the surge of viruses in the fish species of Lake Tanganyika. They acknowledged that while they cannot definitively state a link between cosmic events and the emergence of new aquatic viruses, there is a temporal correlation that is noteworthy.

An unexpected finding was that both the explosion of a distant star and the increase in local viruses appeared to overlap in time. Data on iron-60, an isotope made by stellar explosions, helped researchers trace the origin of that star, suggesting our solar system moved through a gas-sparse region known as the Local Bubble, shaped by numerous ancient supernovae. Scientists believe this journey exposed Earth to more cosmic rays, which might encourage mutations that could impact biological outcomes.

Further questions remain, especially concerning how cosmic rays might speed up viral mutations, specifically in the unique environment of Lake Tanganyika, known for its isolated species. Researchers theorize that when these rays damage DNA strands, the process of viral replication may change, resulting in increased diversity.

Even though the supernova took place tens of thousands of years ago, the implications still matter today. Some scientists are investigating whether modern species still show traces of ancient mutations caused by cosmic energy. Others focus on current levels of cosmic radiation, speculating if another stellar explosion might yield similar effects.

Nojiri plans to pursue a doctorate in astrophysics, motivated by her curiosity about cosmic events and their potential influence on life on Earth. Her research examines how cosmic rays from ancient supernovae might have impacted the evolution of life in various ecosystems. Ongoing studies intend to unveil how these distant cosmic forces can yield surprising effects on living organisms. The hope is that her work will encourage future scientists to delve into the profound connections between the universe and life on Earth.