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Wash U. professor looks at what's happening on Jupiter's moon

Ganymede, Jupiter's largest moon, has a large bulge at its equator.
Ganymede, Jupiter's largest moon, has a large bulge at its equator.

Something strange has happened on Ganymede, this solar system’s largest moon. Orbiting Jupiter, planetary experts discovered it has a large icy bulge.

“We were basically very surprised,” said William McKinnon, a professor in Washington University's Earth and Planetary Sciences Department. “It’s like looking at old art or an old sculpture. We looked at old images of Ganymede taken by the Voyager spacecraft in the 1970s that had been completely overlooked, an enormous ice plateau, hundreds of miles across and a couple miles high.”

“It’s like somebody came to you and said, ‘I have found a thousand mile wide plateau in Australia that was six miles high.’ You’d probably think they were out of their minds or spent too much time in the Outback,” McKinnon said.

McKinnon collaborated with Paul Schenk of the Lunar and Planetary Institute on the discovery. Schenk earned his Ph.D. from Washington University.

But what does it all mean?

McKinnon said it confirms the idea that there’s an ocean on Ganymede below all of that ice. And, he said it’s unusual because the moon is mostly flat.

The threat of asteroids striking Earth

Relative to Earth, Jupiter is a massive planet. With that mass comes great gravity and Jupiter’s gravity is what sends asteroids toward Earth. 

“When we talk about asteroids killing the dinosaurs or being a threat to civilization, we can ultimately point our finger at Jupiter’s gravity,” McKinnon said.

McKinnon said the Earth is not in imminent danger from an asteroid and if it was, there would be many decades to figure it out.

“It will happen again but we are smarter than the dinosaurs so we can prevent any further problems if we’re just wise about it.”

McKinnon said it would not be wise to blow up an asteroid because that would simply spread the pieces. “You want to nudge the asteroid,” he said. “You’d want to nudge the asteroid to change its course, put an engine on it.”

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