Jupiter Just Saved Earth...

...or so some believe. But others disagree. That controversy is today's curriculum.

"Jupiter took a bullet for us last weekend.

"An object, probably a comet that nobody saw coming, plowed into the giant planet’s colorful cloud tops sometime Sunday, splashing up debris and leaving a black eye the size of the Pacific Ocean. This was the second time in 15 years that this had happened. The whole world was watching when Comet Shoemaker-Levy 9 fell apart and its pieces crashed into Jupiter in 1994, leaving Earth-size marks that persisted up to a year.

"That’s Jupiter doing its cosmic job, astronomers like to say. Better it than us. Part of what makes the Earth such a nice place to live, the story goes, is that Jupiter’s overbearing gravity acts as a gravitational shield deflecting incoming space junk, mainly comets, away from the inner solar system where it could do for us what an asteroid apparently did for the dinosaurs 65 million years ago. Indeed, astronomers look for similar configurations — a giant outer planet with room for smaller planets in closer to the home stars — in other planetary systems as an indication of their hospitableness to life.

"Anthony Wesley, the Australian amateur astronomer who first noticed the mark on Jupiter and sounded the alarm on Sunday, paid homage to that notion when he told The Sydney Morning Herald, “If anything like that had hit the Earth it would have been curtains for us, so we can feel very happy that Jupiter is doing its vacuum-cleaner job and hoovering up all these large pieces before they come for us.”

"But is this warm and fuzzy image of the King of Planets as father-protector really true?"

THE OTHER SIDE

"Jupiter is just as much a menace as a savior, he said. The big planet throws a lot of comets out of the solar system, but it also throws them in." [Quotes are excerpts from New York Times 7/26/09 "Juipter: Our Cosmic Protector" by Dennis Overbye]

PERSONALLY, I think this is a mathematical question. Obviously Jupiter deflects some passing objects toward and some away from earth and the question is how many in each column? Someone (not me) could do a computer simulation of objects (comets, etc.) traveling inward from the outer solar system and how they are affected by Jupiter's gravity. That should give an informed answer. Or at least as informed as we can be based on our knowledge and assumptions about the overall distribution of masses and trajectories of outer solar system objects heading inward.