Day: May 29, 2017

The first science findings from NASA’s Juno mission were published at the end of May 2017, revealing Jupiter to be far more complex a world than had been previously envisioned.

The Juno mission hopes to answer many questions about Jupiter – the structure and composition of its atmosphere, a greater understanding of the forces driving that atmosphere and the distinctive upper layer cloud formations, its magnetic field, weather patterns, and so on. It is also hoped the mission will resolve the question of what actually lies at Jupiter’s core.

Two theories have tended to dominate thinking around the latter: that Jupiter either has a relatively compact solid core 1 to 10 times as massive as Earth or it has no solid core at all, just gases compressed to a liquid state. However, the data returned by the spacecraft since it arrived in orbit around Jupiter in July 2016 doesn’t support either hypothesis. Instead, it suggests Jupiter has a large, partially dissolved core of ices and rock.

This conclusion comes via measurements of the magnitude planet’s magnetic field, which has not only proven to be significantly higher than expected, but also exhibits large spatial variations, being significantly higher than expected in some locations, and markedly lower in others. These results suggest that Jupiter’s core has a molecular hydrogen layer which appears to be the dynamo layer driving Jupiter’s magnet field, sitting over a metallic hydrogen layer which gradually transitions into a “fuzzy core” of ices and rock.

The Juno data also suggest the turbulent “meteorological layer” of Jupiter’s atmosphere, where the familiar bands of cloud exist, extends downwards more than 1,000 km (625 mi), with the tropical zoning of banded cloud layers extending down to pressures of up to 100 bars – or 100 times Earth’s air pressure at sea level), before transitioning to slightly less turbulent regions.

It had been thought that somewhere beneath the cloud layers the gasses present in the atmosphere would be more well mixed. But again, the Juno data suggests otherwise. “We’re finding that that’s just not true at all,” Dr. Scott Bolton, Juno’s principal investigator said as the first set findings was published on May 25th. “There’s structure down deep, but it doesn’t seem to match the zones and belts. And so we’re still trying to figure it out.”

“What we’ve learned so far is earth-shattering. Or should I say, Jupiter-shattering,” he also stated. “Discoveries about its core, composition, magnetosphere, and poles are as stunning as the photographs the mission is generating. Juno is re-writing all we thought we knew about Jupiter.” It is also adding new mysteries to Jupiter’s story as well.

One of the most remarkable aspects of the Juno mission so far have been the amazing images of the planet’s north and south polar regions. Rather than being banded, as with the rest of the atmosphere, or uniformly regimented into a geometric form, like Saturn’s north polar region, the atmosphere over Jupiter’s poles is a chaotic mix of swirling cyclones and storms, some of them 1,400 km (870 mi) across, towering bove the bluish backdrop of Jupiter’s deeper atmosphere.

“it’s ‘s unclear what, exactly, drives these polar cyclones,” Bolton states. “Over the course of the mission, we’ll be able to watch the poles and see how they evolve. Maybe these cyclones are always there, but maybe they just come and go.”

Juno has also suggested the cause of Jupiter’s auroral displays might be more complex than previously thought.

Earth’s auroras result when the solar wind — charged particles streaming from the sun — are funnelled by the planet’s magnetic field to slam into the atmosphere over the north and south pole in a complex two-way interaction which results in the glow of the northern and southern lights.

It had been thought to be the massive flux tube linking the polar regions of Io, Jupiter’s innermost Galilean moon, and Jupiter’s own polar regions was the driver of the planet’s auroral displays thanks to the 5 million ampere electrical current flowing through the flux. However, data from Juno, which has been combined with observations from Japan’s Hisaki  satellite and the Hubble Space Telescope suggest the gases spreading outward from Io as a result of its extreme volcanism, undergo a complex interaction with the “shock wave” formed by the solar wind as it strikes the outer limits of Jupiter’s massive magnetic field.

This interaction deflects energy from the gases back towards Jupiter at velocities of between 400 and 800 kilometres a second (250 and 500 miles per second). When this energy strikes and penetrates Jupiter’s atmosphere, it gives rise to bright, transient aurora. In addition, it is being theorised that this energy, when it reaches icy Europa and Ganymede – both of which are thought might harbour basic life in the oceans beneath their icy crusts, could provide support for chemical processes on their icy surfaces. This is liable to be something scientists will be considering carefully as more data from Juno is scrutinised.

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