Scientists have been patiently vacuuming ocean floors and were surprised at their unexpected prize. They found extraterrestrial dusts that may help them understand more supernovae. Supernovae are brought about by an explosion of a star about to die. The explosion is so massive that the fireworks can be seen in the entire galaxy for several days.
“Small amounts of debris from these distant explosions fall on the earth as it travels through the galaxy,” said lead researcher Anton Wallner, from the Research School of Physics and Engineering at the Australian National Univ.
“We’ve analyzed galactic dust from the last 25 million years that has settled on the ocean and found there is much less of the heavy elements such as plutonium and uranium than we expected.”
What scientists believed was some of the materials essentials for human survival like iron, potassium and iodine are created and found all over the universe. But their sea scouring venture has presented them something different compared to the present theories about supernovae.
Metallic elements such as lead, silver and gold are also created by supernovae including heavy and radioactive metals such as uranium and plutonium.
Plutonium, is considered a natural time piece based on its radioactive decay. It has a half-life of 81 million years, according to Wallner’s team who made a study about it.
“Any plutonium-244 that existed when the earth formed from intergalactic gas and dust over four billion years ago has long since decayed,” Wallner said.
“So any plutonium-244 that we find on earth must have been created in explosive events that have occurred more recently, in the last few hundred million years.”
The research group made an analysis involving 10 centimeter deep of the earth’s crust representing 25 million years of buildup. Deep-sea sediments were also collected from the Pacific Ocean’s floor but only from stable areas.
“We found 100 times less plutonium-244 than we expected,” Wallner said.
“It seems that these heaviest elements may not be formed in standard supernovae after all. It may require rarer and more explosive events such as the merging of two neutron stars to make them.”
“The fact that these heavy elements like plutonium were present, and uranium and thorium are still present on earth suggests that such an explosive event must have happened close to the earth around the time it formed”, said Wallner.
“Radioactive elements in our planet such as uranium and thorium provide much of the heat that drives continental movement, perhaps other planets don’t have the same heat engine inside them,” he said.