The Possibility of Melting Greenland's Ice Revealing Earth's Oldest Forms of Life
If the catastrophic ice melt in Greenland has a silver lining, it's the potential pushback of Earth's 3.7-billion-year-old life tape threshold due to climate change. This was revealed to me in an email conversation with Paul Bierman, geoscientist and author of "When the Ice is Gone."
Situated in Greenland's largest city, Nuuk, are the world's oldest rocks, forming between 3.8 and 3.7 billion years ago, just 700 million years after Earth's formation. Bierman explains in his book how these rocks were metamorphosed by Earth's plate tectonics and moved poleward, raising the question of whether they might hold evidence of Earth's earliest life.
Earth's plate tectonics not only metamorphosed the Isua rocks but also relocated them thousands of miles from their initial formation sites. This process also helped in the formation of mountain ranges via the movement of large crustal plates.
Although various Greenland microfossils have been proposed over the last 50 years, many have been debunked, especially the older ones. But there remains hope that the melting ice might reveal signs of Earth's earliest biosphere.
Keyron Hickman-Lewis, a microbial paleontologist at the University of London, believes that new discoveries will be made as the ice retreats. He emphasizes that the proposed 3.7-billion-year-old stromatolites in Isua were identified in an outcrop that became accessible after ice melting.
Stromatolites, formations of sedimentary rock, are created by layers of cyanobacteria, calcium carbonate, and trapped sediment. Although Greenland's earliest stromatolites are no longer considered compelling evidence for life, it's anticipated that a biosphere existed by the time Isua's sedimentary rock layers formed, with potential direct evidence preserved within.
Verifying microfossils in such ancient rocks, however, poses a significant challenge. For microfossils more than 3 billion years old, structural and chemical degradation due to metamorphism at high temperatures and pressures makes trace detection and confirmation extremely challenging.
Even rocks from specific regions like West Greenland and Nuvvuagittuq that are older than 3.5 billion years may not preserve fragile microfossil shapes, according to geologist Stephen Mojzsis.
Despite the challenges, ongoing ice melt is inevitable. In a scenario with a rapid fall in carbon emissions, global sea levels would still continue to rise for thousands of years, as Greenland and Antarctica's ice melts.
The Greenland Ice Sheet covers a colossal 80% of its enormous island, stretching across 1.7 million square kilometers, roughly three times the size of Texas. Melting the ice sheet would result in a flooding of tens of millions of homes worldwide, making a substantial presence.
With a global temperature increase of just 1.5°C above pre-industrial levels, temperatures that are already prevalent, the ice sheet could potentially disappear from at least northwest Greenland, and perhaps even the entire island.
The prospect of Greenland potentially revealing older signatures of ancient life remains unclear. Stephen Mojzsis, geologist at Hungary's Konkoly Observatory, shares that the age of Earth's earliest life remains a mystery, thus making it unpredictable what might be uncovered up there.
Enrichment Data:
Although current evidence does not directly support the presence of ancient life within the Greenland ice sheet, the region's geological history, like the Greenland Ice Sheet and ancient rock formations such as the Isua Greenstone Belt, provide valuable information about Earth's early life.
Exploring the challenges associated with confirming microfossils helps to understand the difficulties in confirming such findings. Preservation conditions that must be met for microfossils to remain intact, potential contamination, interpretations of structures, access and sampling restrictions, and analytical techniques required for confirmation are all challenges in verifying microfossils in ice sheets or ancient rocks.
While ice melting may reveal exciting findings concerning Earth's early life, the aforementioned challenges in confirming microfossils continue to pose significant barriers.
- The ancient cyanobacteria, presumed to be responsible for forming stromatolites in Greenland's Isua rocks, could potentially provide microfossils that could help confirm Earth's earliest biosphere.
- Despite the intricate challenges in verifying microfossils from rocks over 3 billion years old, such as structural and chemical degradation due to high temperatures and pressures, ongoing ice melt in Greenland might still reveal such fossils.
- The melting of the Greenland Ice Sheet could potentially uncover microfossils from the ice's bottom layers, offering fresh perspectives on the characteristics and existence of life on Earth during its early stages.
