2017-12-14 11:20:03
Trilobites: The Great Red Spot Descends Deep Into Jupiter

11:20, December 14 430 0

NEW ORLEANS — Jupiter's Great Red Spot is not just a skin-deep beauty mark.

Instead, the iconic storm descends at least 200 miles beneath the clouds and possibly much deeper.

That is one of the latest findings of NASA’s Juno spacecraft, which passed directly over the storm in July.

Juno is designed to peer beneath the clouds of Jupiter, the solar system’s largest planet, and its observations have upended scientists’ notions of how a big ball of hydrogen ought to behave. They have not yet come up with a new understanding of Jupiter.

“We just know enough to know we were wrong,” said Scott Bolton, a scientist at the Southwest Research Institute in San Antonio, Texas who is the mission’s principal investigator.

The Juno scientists presented their latest findings this week at a meeting of the American Geophysical Union in New Orleans.

Before Juno, astronomers could only observe the swirling of the cloud tops in the Great Red Spot, which is 10,000 miles wide — large enough to swallow Earth. Last year, scientists using an infrared telescope in Hawaii reported that the atmosphere 350 to 600 miles above the spot was exceptionally hot, averaging 2,500 degrees Fahrenheit.

But no one knew what was happening below the clouds. Scientists wondered whether the storm was shallow and confined to that slice of the atmosphere or if it descended hundreds or thousands of miles into the planet.

An instrument on Juno measures microwave emissions, which pass through the clouds into space. Warmer regions generate more microwaves, and the region below the Great Red Spot was warmer, even 200 miles down, the deepest that the microwave instrument could peer. The deep heat likely explains the source of the energy driving the storm.

Andrew P. Ingersoll, a professor of planetary science at the California Institute of Technology and a member of the Juno team, noted that the roots of the Great Red Spot go down 50 to 100 times deeper than the Earth’s oceans.

“It’s definitely warmer than its surroundings at that great depth,” Dr. Ingersoll said. “That is a new result. How deep it goes beyond that is still T.B.D.”

While the microwave instrument cannot answer that question, additional flyovers by Juno could help build a gravity map of the Great Red Spot region that could identify movements of mass hundreds of miles farther down. Mission managers are aiming for at least one more pass by Juno, which arrived at Jupiter last year and is one-quarter of the way through its mission.

The Great Red Spot has lasted at least 150 years and probably centuries longer. Additional data gathered by Juno could help scientists determine how long the storm will last.

Although it has been resilient, it has been shrinking, and its current size is considerably smaller than earlier measurements. In the late 1800s, it may have been 25,500 miles wide. When the two NASA Voyager spacecraft flew by in 1979, they measured the width at 14,500 miles.