Moon means mining for all Earth-based studies and explorations but giving them a fillip, two new studies have suggested existence of radioactive iron that was deposited on the Earth and Moon two million years ago due to a supernova.
The radioactive iron isotope called 60Fe found in moon’s sample was similar to the one found on Earth’s ocean floor, said scientists from Germany’s Technical University of Munich and the US. The researchers confirm that the radioactive iron substance was produced by the same star about 300 light years away.
“But this can only account for a very small portion of the 60Fe found,” said Dr. Gunther Korschinek, physicist at TUM.
The radioactive iron isotope is said to have a half-life of 2.62 million years, which suggests a short time compared to the age of the solar system that is about 4.6 billion years.
Because of its half-life, the isotopes were not created when the solar system was formed but absorbed when the supernova’s cosmic particles created the radioactive iron, he said.
The research team analyzed lunar samples, gathered by several of the Apollo missions to the moon in the late 1960′s to early 1970’s with the high-sensitivity accelerator mass spectrometer of the Maier-Leibnitz Laboratory near Munich in Germany.
The other study was conducted by Dr. Anton Wallner, a nuclear physicist at the Australian National University Research School of Physics and his team which provided new evidence of not just one but a succession of massive nearby supernova explosions.
Wallner’s team found evidence of stellar remains in 120 samples of the 60Fe isotope gathered from the bottom of the Pacific, Atlantic and Indian Oceans. These 60Fe isotopes were from between 1.7 to 3.2 million years ago and produced by supernovae less than 300 light years away.
“We were very surprised that there was debris clearly spread across 1.5 million years,” said Wallner. “It suggests there were a series of supernovae, one after another.”
The moon is also known for its abundant rare-earth elements for which China is keen to explore with its 2013 Jade Rabbit lander. It has a solid iron-rich inner core with a radius of 240 km and a fluid outer core primarily made of liquid iron with a radius of roughly 300 km.