Remnants from Earth’s birth linger 4.5 billion years later
Traces of a long-extinct isotope give insight into planet’s origin
LOTTA LAVA The 60-million-year-old flood basalts of the North Atlantic Igneous Province (an area that includes the rocky outcroppings in Baffin Bay, shown) contain isotope traces that originated over 4.5 billion years ago.
Don Francis
Shaken-but-not-stirred remnants of Earth’s earliest years still exist nearly 4.6 billion years later.
Researchers traced the shadowy footprints of an isotope that hasn’t existed for over 4.5 billion years to much younger lava rocks from the Pacific and Atlantic oceans. That suggests that reservoirs of the ancient mantle may be hidden deep inside the planet, geochemist Hanika Rizo and colleagues report May 13 in Science.
Earth formed about 4.6 billion to 4.5 billion years ago as planetary bodies collided, disintegrating and melting to accrete into one mass like a hot, rocky lint ball. Geologists have assumed that any relics of this bumpy beginning were mixed beyond recognition.
Instead, Rizo’s team found a surprise: Some modern flood basalts have unusually high concentrations of tungsten-182. That’s significant because that isotope forms only from
