There's Something Strange Going On Inside Neptune

By David Crookes , All About Space magazine 5 hours ago Science & Astronomy

Space Mysteries: The ice giant is further away than Uranus, yet their surface temperatures are remarkably similar.



Something mysterious is going on inside the ice giant Neptune.
(Image: © All About Space/Tobias Roetsch)

When Voyager 2 reached Neptune in 1989, just 12 years after setting off on its historic journey through the solar system, it discovered six new moons, took the first images of the planet's rings and noted a particularly violent storm.

The storm was something of a surprise. In the southern hemisphere there was a swirling, counter-clockwise wind of up to 1,500 mph (2,414 km/h) — the strongest ever recorded. Astronomers called it the Great Dark Spot, and while it had gone by the time the Hubble Space Telescope looked at the planet five years later, they were keen to learn why the winds were so extreme.

They were also perplexed by another issue: Voyager 2 revealed that Neptune is warmer than Uranus, despite being further from the sun. As physicist Brian Cox discussed in his BBC documentary, The Planets: "The source of this extra heat remains a mystery." But does that mean we have a double-puzzle on our hands, and can one mystery help to explain the other in some way?

Before we begin to address the two issues at hand, we must first look at what is actually meant by "warmer". Since Neptune is a gas giant, we cannot test the globally average temperature at ground level in the way that we could on Earth's solid surface. Instead, with Neptune's core likely to be small, temperature measurements must be taken at an altitude. Trouble is, which one?

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