NASA’s Juno has made its first close pass to Jupiter, revealing secrets about its atmosphere and interior that challenge previous assumptions about the giant gas planet. The Juno mission, which launched in 2011 and began its first orbit last year, allows scientists to view Jupiter in new ways thanks to the probe's highly elliptical orbit, which passes over the planet's poles and dives within 5,000km (3,100 miles) of its cloud tops.
Now the NASA probe has captured new images of the gas giant's chaotic cyclones, which are up to 1,400km (870 miles) across, roughly the length of Japan.
A NASA statement described the planet as 'a complex, gigantic, turbulent world' that is far different than scientists previously thought. Two papers in the journal Science and 44 papers in Geophysical Research Letters describe a trove of discoveries made since Juno began orbiting Jupiter last year.
“We knew, going in, that Jupiter would throw us some curves. There is so much going on here that we didn't expect that we have had to take a step back and begin to rethink of this as a whole new Jupiter. Juno's findings are 'really going to force us to rethink not only how Jupiter works, but how do we explore Saturn, Uranus and Neptune.” said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio.
With dozens of cyclones hundreds of miles across - alongside unidentifiable weather systems stretching thousands of miles - the poles look nothing like Jupiter's equatorial region, instantly recognizable by its stripes and Great Red Spot, a raging hurricane-like storm.
“That's the Jupiter we've all known and grown to love. And when you look from the pole, it looks totally different ... I don't think anybody would have guessed this is Jupiter.” Bolton said.
He calls these first major findings 'Earth-shattering. Or should I say, Jupiter-shattering.'
A look at Jupiter's poles has shown they are covered with dozens of densely clustered storms, possibly dropping hail or snow. 'Images of Jupiter's previously-unseen poles show a chaotic scene of bright oval features,' said one of the studies in the journal Science.
These ovals, it turns out, are huge swirling storms, some of which measure up to 870 miles (1,400 kilometers) across. Researchers found 'signs of ammonia welling up from the deep atmosphere and forming giant weather systems.' Now, more study is needed to better understand the nature of Jupiter's storms, and why the planet acts this way.
Juno has also revealed data regarding Jupiter's swirling magnetic fields, which are up to ten times stronger than the magnetic forces acting on Earth. This will help understand the structure of the planet's atmosphere and whether it has a solid core, as models have predicted. Analysis of the gas giant's magnetic field reveals that close to the planet, the field greatly exceeded expectations - it is substantially stronger than models predicted, at 7.766 Gauss, or roughly ten times Earth's magnetic field.
“Juno is giving us a view of the magnetic field close to Jupiter that we've never had before. Already we see that the magnetic field looks lumpy: it is stronger in some places and weaker in others. This uneven distribution suggests that the field might be generated by dynamo action closer to the surface, above the layer of metallic hydrogen. Every flyby we execute gets us closer to determining where and how Jupiter's dynamo works.” said Jack Connerney, Juno deputy principal investigator and the lead for the mission's magnetic field investigation at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
NASA's enhanced-color image of a mysterious dark spot on Jupiter shows a Jovian 'galaxy' of swirling storms in this image captured by NASA's Juno spacecraft on February 2, 2017, at 5:13 a.m. PDT (8:13 a.m. EDT), at an altitude of 9,000 miles (14,500 kilometers) above Jupiter's cloud tops.
The complexity and richness of Jupiter's 'southern lights' are on display in this image of false-color maps from Nasa's Juno spacecraft
Juno also is designed to study the polar magnetosphere and the origin of Jupiter's powerful auroras—its northern and southern lights. These auroral emissions are caused by particles that pick up energy, slamming into atmospheric molecules. Juno's initial observations indicate that the process seems to work differently at Jupiter than at Earth.
Juno is in a polar orbit around Jupiter, and the majority of each orbit is spent well away from the gas giant. But, once every 53 days, its trajectory approaches Jupiter from above its north pole, where it begins a two-hour transit (from pole to pole) flying north to south with its eight science instruments collecting data and its JunoCam public outreach camera snapping pictures. The download of six megabytes of data collected during the transit can take 1.5 days.
“Every 53 days, we go screaming by Jupiter, get doused by a fire hose of Jovian science, and there is always something new. On our next flyby on July 11, we will fly directly over one of the most iconic features in the entire solar system -- one that every school kid knows - Jupiter's Great Red Spot. If anybody is going to get to the bottom of what is going on below those mammoth swirling crimson cloud tops, it's Juno and her cloud-piercing science instruments.” said Bolton.
In one study, researchers analysed results from Juno's flight just above the cloud tops.
Images of Jupiter's previously-unseen poles show a chaotic scene of bright oval features, very different from Saturn's polar regions. A time-lapse of Juno images reveals that the ovals are cyclones, some of which reach diameters up to 1,400km (870 miles) across.
Juno measured the thermal structure of Jupiter's deep atmosphere as it passed over the cloud tops. These data show unexpected structures, which the authors interpret as signs of ammonia welling up from the deep atmosphere and forming giant weather systems. In a second study, researchers studied Jupiter's auroras and its magnetosphere, the region where the planet's magnetic field dominates over the solar wind.
Juno encountered the giant planet's bow shock, essentially a stationary shockwave, as it entered the magnetosphere on 24 June 2016. Since the spacecraft only encountered one bow shock as it approached the planet, compared to multiple encounters on subsequent orbits, this suggests that the magnetosphere was expanding in size at the time, according to researchers.
Taking advantage of its unique perspective when positioned above the poles, Juno detected downward-travelling electron beams that shower energy into Jupiter's upper atmosphere, potentially powering the huge auroras that Juno saw in ultraviolet and infrared images. Intriguingly these electron showers appear to have a different distribution from those that occur on Earth, suggesting a radically different conceptual model of Jupiter's interaction with its space environment, researchers said.
“The results from Juno's initial close passes of Jupiter are changing our understanding of this gas giant. Juno's direct glimpse of Jupiter's poles shows numerous cyclonic storms clustered together and a storm illuminated in Jupiter's nightside that provided a measurement of its vertical extent.
The deep microwave sounding of Jupiter by Juno demonstrates the power of this technique for unveiling spatial and temporal structure in the ammonia abundance. The initial measurement of Jupiter's gravity will inform interior models with implications for the extent, existence, and mass of Jupiter's core.” researchers from the Southwest Research Institute in San Antonio, Texas, said in a scientific paper.
The research was published in the journal Science. The solar-powered Juno spacecraft launched in 2011, and made its first tour around Jupiter on August 27, 2016. Juno moves in an elliptical orbit, skimming within 3,100 miles (5,000 kilometers) of Jupiter's cloud tops and passing over the poles.
Juno's mission is scheduled to end in February 2018, when the probe will self-destruct by diving into the planet's atmosphere. The $1.1 billion project aims to peer beneath the clouds around Jupiter for the first time to learn more about the planet's atmosphere and how much water the planet contains.