In a significant geological discovery, scientists have uncovered one of the oldest asteroid impacts on Earth, situated in the remote North Pole Dome area of northwest Australia. Initially believed to date back over a billion years, this impact is linked to the era when Earth was primarily populated by single-celled life forms. The site is characterized by rugged red rocks, formed from ancient lava eruptions approximately 3.47 billion years ago. Scattered throughout the landscape are sandstones that house some of the oldest microbial fossils on the planet, which thrived in hydrothermal pools and shallow marine environments. According to geological research published in Science Advances, these findings provide insights not only into the history of life on Earth but also serve as a crucial analog for studying potential life on Mars, a planet that experienced wet conditions suitable for life during the same time frame.
The North Pole Dome structures serve as vital analogs for Mars, particularly due to their geological evolution. Geologist Alec Brenner states that the rocks in this area closely resemble Martian surface formations from 3 to 4 billion years ago. Given that Mars may have supported life during its watery past, the new findings can help scientists better predict how ancient Martian microbial fossils might be altered by environmental factors such as fluid flows or meteor impacts. These alterations can obscure genuine fossils or create misleading structures. Brenner emphasizes that understanding the consequences of asteroid impacts on early life provides a template for astrobiologists aiming to discover and validate potential fossils on Mars.
The early Earth and Mars shared tumultuous histories marked by asteroid impacts, which shaped their respective surfaces. While Earth has a history of erosion and tectonic activity that has largely erased its oldest craters, the Moon and Mars still bear testament to these colossal impacts with visible craters. Interestingly, the discovery of the Miralga impact structure is particularly noteworthy because it was found in an area historically examined by geologists. Brenner stumbled upon it while driving across North Pole Dome in 2023. He noticed unique cone-shaped rocks, known as "shatter cones," which are formed by the shock waves of an impact event. Currently, the crater itself is believed to have been eroded away, revealing the geological features beneath that were affected by the impact.
This striking find was made with the collaboration of researchers who meticulously mapped hundreds of shatter cones across a 7-kilometer stretch. These cones were oriented towards the central point of the impact, indicating the direction of the meteorite’s strike. The research indicates that a meteorite, estimated to be between 1 to 2 kilometers wide, struck Earth, producing a crater with a diameter of approximately 16 kilometers. While most of the rocks studied are about 3.47 billion years old, some shatter cones extended into a younger rock layer of 2.77 billion years, suggesting that the impact occurred sometime between 1.2 to 1.8 billion years ago.
Aaron Cavosie, an impact geologist, is particularly excited by the geological evidence suggesting that Earth’s oldest craters have largely disappeared due to natural geological processes, unlike those on Mars and the Moon. The shatter cones contain unique titanium minerals, which have undergone shock deformation due to the impact, providing invaluable insights into the pressure and temperature conditions at the time. This discovery shows how Earth’s geological history can serve as a comparative framework for understanding the potential for life on Mars.
The volcanic basalts and rock formations found at the impact site resemble those present on Mars, particularly in regions like Jezero Crater, which potentially held water billions of years ago. NASA’s Perseverance rover has been exploring this area to uncover signs of past microbial life, providing additional context for the significance of the Australian findings. Brenner’s research allows scientists to return to early Earth’s environments with a fresh perspective, offering the potential to reinterpret ancient fossils while also informing the ongoing exploration for life on Mars. This research underscores the importance of Earth’s geological history in exploring planetary conditions that foster life.
