Microorganisms trapped beneath Antarctic ice for up to eight million years have successfully grown in laboratory tests after being thawed by researchers.
Scientific analysis of five ice samples recovered from Beacon Valley and Mullins Valley revealed that while ancient bacteria can survive frozen for millions of years, their genetic material suffers progressive degradation over time.
The analyzed ice samples ranged in age from 100,000 years to eight million years. Laboratory tests showed a clear difference in revival speed depending on how long the microbes had been encased in ice.
Microorganisms recovered from the youngest ice samples grew rapidly once thawed. In contrast, microbes extracted from the oldest eight-million-year-old ice required approximately 70 days to double their population.
DNA degradation in ancient ice
Genetic examination of the revived organisms demonstrated that the size of DNA fragments decreased exponentially as the age of the ice increased. The researchers calculated a half-life of approximately 1.1 million years for DNA preservation under cold Antarctic conditions.
In the oldest ice samples, the remaining DNA fragments had an average length of just 210 base pairs. By comparison, a typical bacterial genome contains nearly three million base pairs, demonstrating severe structural damage to the genetic code.
Base pairs are the paired chemical building blocks that make up the structure of DNA and store genetic information. When DNA breaks down into short fragments, cells struggle to repair the damage and perform essential biological functions.
The findings indicate that while freezing temperatures can preserve cell structures and keep microorganisms viable for millions of years, ice cannot entirely prevent the breakdown of genetic material.
Implications for panspermia theory
The progressive degradation of genetic material poses major questions for the concept of panspermia. Panspermia is the scientific hypothesis that microorganisms or biological material could travel between planets or solar systems inside comets, meteorites, or debris launched by giant impacts.
The research does not completely rule out the possibility of panspermia. However, it highlights the immense difficulty of preserving intact genetic information across vast stretches of time.
If DNA fragments significantly over millions of years while shielded inside Antarctic ice, organisms traveling through interstellar space would face even greater obstacles. Space travel exposes biological material to intense cosmic radiation and extreme temperature shifts.
Because of these factors, the researchers concluded that the results make it unlikely that life on Earth originated from outside the solar system through incoming genetic material.
