Researchers from Norway, Germany and Britain have suggested that the Indian Ocean is harboring fragments of ancient continental crust.
Those fragments, the researchers said in Nature Geoscience, lie buried beneath more recent oceanic crust erupted by underwater volcanoes. A number of places in the Indian Ocean, such as Madagascar, Mauritius and the Seychelles, Maldives and Lakshadweep islands, are known to display a slightly stronger gravitational field than expected — an anomaly that could be explained by abnormally thick crust. If that's the reason, it could be because the crust is about 15 miles thick, resembling continental crust, compared with the 3 to 6 miles of oceanic crust elsewhere.
In search of chemical evidence, the researchers took sand samples from Mauritius. Its surface rock is made from volcanic oceanic crust, or basalt. But its beach sands contained not just fragments of eroded lava but also zircons, a mineral associated with continental crust. The zircons from Mauritius, it turned out, were hundreds or even thousands of millions of years old, although the island's oceanic crust was less than 10 million years old. Geophysicist Trond Torsvik of the University of Oslo believes the zircons were in the lava that punched its way through pieces of pre-existing continental crust on the seafloor.
nasa spots third band of radiation
NASA probes that are exploring the treacherous twin Van Allen radiation belts encircling the Earth spied a third, unexpected band of radiation that burst into view and then disappeared, scientists report.
The NASA probes spotted the temporary band of high-energy electrons just three days after launch. The discovery has stunned scientists and is forcing a rethink of the radiation environment above Earth, with implications for proposed human deep-space missions. Researchers are now puzzling over the temporary band of high-energy electrons — why it did not quickly merge with the outer belt, as predicted by current understanding of the physics of the region.
"We don't know why we haven't seen this before," said mission scientist Shri Kanekal, a co-author of a report published online in Science. "We don't know if it's a rare phenomenon. Even after 50 years, nature is still capable of surprising us."
Being able to predict such sudden increases in near-Earth radiation could help steer future human space missions away from dangerous doses.