A diamond-studded black pebble from Egypt is reportedly the first-ever evidence of a comet striking Earth. A team of scientists analyzing the rock, which was discovered by a geologist in the Egyptian desert a few years ago, concluded that is the first known nucleus of a comet rather than material from a meteorite. “Comets always visit our skies — they’re these dirty snowballs of ice mixed with dust — but never before in history has material from a comet ever been found on Earth,” David Block, a professor at Wits University in Johannesburg, said in a release. About 28 million years ago, the comet struck Earth’s atmosphere and exploded, unleashing a shock wave of fire and heating up the sand beneath it to about 2,000 degrees Celsius, according to the release. The hot sand created a scattering of yellow silica glass over an area of nearly 4,000 miles. The impact also produced diamonds, which normally form from carbon in areas of very high temperatures and pressures but can also form from shock, explaining the bits of diamond on the comet nucleus. The researchers named the rock Hypatia to honor the first well-known female mathematician, astronomer and philosopher, Hypatia of Alexandria. Read more http://www.weather.com/news/science/comet-struck-egypt-28-million-years-ago-20131009
