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For several million years, the Earth cycled through ice ages at a regular pace, but then, 1.25 million to 700,000 years ago, something changed: ice ages went from lasting 40,000 years to 100,000. … By looking at the microscopic shells of microorganisms called foraminifera, Adam Hasenfratz of the Geological Institute in Zürich, Switzerland, and colleagues, find evidence of a reduction in deep water circulation, causing less carbon dioxide to be released into the air. Oceanic changes in the Antarctic Zone could have ensured “that glacial conditions persisted despite orbital changes to the contrary”, the study says. The new research, presented...

Researchers then scoured the globe for thin layers of radioactive isotopes in rock strata and in 1999 struck figurative gold: Samples from beneath the ocean revealed some hard metallic layers, known as ferromanganese crusts that form slowly over millions of years, containing iron-60, an isotope with a half-life of 2.6 million years -- so short that the material must be much younger than Earth. The iron-60 was in a stratum laid down 2.2 million years ago. Similar layers of iron-60 have since been found elsewhere in the oceans. Astronomers have also been scouring the skies for groups of stars that...

Millions of years ago, a series of nearby supernovae sent radiation and debris raining down to Earth. The events left traces of radioactive iron-60 embedded in the sea floor and even on the Moon, and now, researchers are saying they may have had life-altering effects on the early inhabitants of our planet. At just hundreds of light-years away, two major stellar explosions may have spurred changes to the environment, and even increased the rates of cancer and mutation.

An international team of scientists has found evidence of a series of massive supernova explosions near our solar system, which showered Earth with radioactive debris. The scientists found radioactive iron-60 in sediment and crust samples taken from the Pacific, Atlantic and Indian Oceans. The iron-60 was concentrated in a period between 3.2 and 1.7 million years ago, which is relatively recent in astronomical terms, said research leader Dr Anton Wallner from The Australian National University (ANU). "We were very surprised that there was debris clearly spread across 1.5 million years," said Dr Wallner, a nuclear physicist in the ANU Research...