Thursday, November 20, 2008

An asteroid twofer.....

Ever notice that every now and then all you see is one type of science article? Seems every time I look there is something about asteroids. One I found interesting in Discovery News talks about a possible asteroid impact some 2300 years ago off New York City. Studies of the Hudson river silt suggest an asteroid 330 feet in diameter slammed into the Atlantic Ocean nearby. The evidence of the impact takes the form of carbon spherules -- perfectly round particles that form in the extreme pressures of an impact. These particles were discovered by a team of researchers from Harvard.
Read more in Discovery News There is also a really neat animation showing how the proposed wave would have washed inland carrying with it proof if the impact.

The other article, sent in by Shaun Saunders, deals with Mars' lack of a magnetic field. Up until 5 billion years ago, Mars closely resembled Earth. Roughly 4.2 billion years ago Mars was suddenly pummeled with at least 20 asteroids between 124 and 311 miles in diameter, each leaving a crater. By contrast, the object thought to have killed of the dinosaurs on Earth is estimated to have been five to six miles wide. One of the last giant meteors blew a hole 1,864 miles wide in the planet, creating Utopia basin in the planet's northern hemisphere. At about 4.1 billion years old, Utopia is the oldest crust on the planet that doesn't show signs of magnetism, meaning the rocks must have cooled at a time when there was no magnetic field.
Read the MSNBC article that describes the dynamics taking place that would shut down Mars' magnetic field, which ultimately destroyed the planet's ability to maintain an atmosphere.

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