“A gift, perhaps, from our friend and lord, Jupiter.”

In the comments zone of a previous post on the topic, Malachi blasphemously suggested that the Great Black Spot [of Jupiter] was proof of an intelligent designer. [Should I get the beards ready? – Ed] In the New York Times, a report points out that the gas giant’s influence is not always so benign.

Take, for example, Comet Lexell, named after the Swedish astronomer Anders Lexell. In 1770 it whizzed only a million miles from the Earth, missing us by a cosmic whisker, Dr. Marsden said. That comet had come streaking in from the outer solar system three years earlier and passed close to Jupiter, which diverted it into a new orbit and straight toward Earth.

The comet made two passes around the Sun and in 1779 again passed very close to Jupiter, which then threw it back out of the solar system. “It was as if Jupiter aimed at us and missed,” said Dr. Marsden, who complained that the comet would never have come anywhere near the Earth if Jupiter hadn’t thrown it at us in the first place.

And, as the report also suggests, it’s not necessarily comets we should be worrying about.

Asteroids pose the greatest danger of all to Earth, however, astronomers say, and here Jupiter’s influence is hardly assuring. Mostly asteroids live peacefully in the asteroid belt between Mars and Jupiter, whose gravity, so the standard story goes, keeps them too stirred to coalesce into a planet but can cause them to collide and rebound in the direction of Earth.

That’s what happened, Greg Laughlin of the University of California at Santa Cruz, said, to a chunk of iron and nickel about 50 yards across roughly 10 million to 100 million years ago. The result is a hole in the desert almost a mile wide and 500 feet deep in northern Arizona, called Barringer Crater. A gift, perhaps, from our friend and lord, Jupiter.

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