Category: Jupiter

Robotic spacecraft can gather a lot of data, and sometimes it takes years to sort through all the information acquired. Case in point: The Galileo spacecraft orbited Jupiter from 1995-2003. One discovery made by this mission was an anomaly in Jupiter’s rings. For the most part, the rings fall into the standard model of ring formation where the ring particles are shepherded by the orbits of four of Jupiter’s moons; Adrastea, Metis, Amalthea and Thebe (closest to farthest.) But a faint outward protrusion of dust extends beyond the orbit of Thebe, and scientists were mystified why this was occurring.

But a new study of data from the Galileo mission has found that this extension results from the interplay of shadow and sunlight on dust particles that make up the rings.

“It turns out that the outer ring’s extended boundary and other oddities in Jupiter’s rings really are ‘made in the shade,'” said Douglas Hamilton, a professor of astronomy at the University of Maryland. “As they orbit about the planet, dust grains in the rings alternately discharge and charge when they pass through the planet’s shadow. These systematic variations in dust particle electric charges interact with the planet’s powerful magnetic field. As a result small dust particles are pushed beyond the expected ring outer boundary, and very small grains even change their inclination, or orbital orientation, to the planet.”

The Galileo spacecraft was deliberately maneuvered to plunge into Jupiter in 2003 in an effort to protect one of its own discoveries – a possible ocean beneath the icy crust of the moon Europa (scientists didn’t want the spacecraft to one day impact and possibly contaminate Europa.) During this maneuver, the spacecraft dove through the rings and registered thousands of impacts from dust particles with its supersensitive dust detector.

Hamilton and German co-author Harald Krüger studied the impact data on dust grain sizes, speeds, and orbital orientations. Krüger analyzed the new data set and Hamilton created elaborate computer models that matched dust and imaging data on Jupiter’s rings and explained the observed unexpected behavior.

Take a look at Hamilton’s incredible models here.

“Within our model we can explain all essential structures of the dust ring we observed, ” said Krüger.

According to Hamilton, the mechanisms they identified affect the rings of any planet in any solar system, but the effects may not be as evident as it is at Jupiter. “The icy particles in Saturn’s famous rings are too large and heavy to be significantly shaped by this process, which is why similar anomalies are not seen there, ” he said. “Our findings on the effects of shadow may also shed some light on aspects of planetary formation because electrically charged dust particles must somehow combine into larger bodies from which planets and moons are ultimately formed.”

Original News Source: University of Maryland press release

Jupiter is a spotty place. There’s the aptly-named Great Red Spot – a large, long-lasting storm – that we all know and love, and new storms crop up every so often to create interesting features for astronomers both professional and amateur to study. The most recent discovery of new spots can only be seen in the UV, but they add a whole new level of complexity for scientists to chew on.

Io, one of Jupiter’s many moons, is volcanically active, and eruptions on the moon spew sulfur into the system. This sulfur is then ionized and swept up by Jupiter’s strong magnetosphere. Interactions between the ions and the magnetosphere cause aurora in the UV spectrum, similar to the phenomenon that makes the Northern Lights shine here on Earth. Io leaves a so-called ‘footprint’ on Jupiter in this way, and creates a glowing spiral shape on the northern and southern poles of the planet.

The rotation of Jupiter causes the spiral shape of the aurora: Io is ‘connected’ in one spot, and as Jupiter rotates it draws a glowing swirl of UV light around the pole. Astronomers had previously seen spots ‘downstream’ from the main spot caused by the interaction with Io, but these new images show a faint leading spot in front of the main one, essentially “upstream” in the flow of particles that causes the phenomenon.

A team from the University of Liège in Belgium discovered the spots in ultraviolet Hubble images taken of Jupiter. They found that when there were faint leading spots in one of the hemispheres, there were multiple spots in the other. The researchers propose that a beam of electrons is being transferred from one hemisphere to another, causing the fainter spots. The results of the study were published in the most recent edition of Geophysical Research Letters.

The image below illustrates the different mechanisms creating the auroral spots. The large torus around Jupiter is the plume of sulfur created by Io. The blue line between Io and Jupiter is where it is connected by the ionized sulfur, drawn in and funneled by Jupiter’s magnetosphere. The red lines illustrate the possible electron beams connecting the poles, which create the newly-discovered spots.

When Hubble is repaired in August, the researchers hope to take a closer look at the phenomenon and better understand this complex interaction.

Source: Eurekalert

Jupiter has a powerful magnetic field 20,000 times stronger than the Earth’s. It is therefore of no surprise that the highly energetic and damaging particles flying around in the Earths Van Allen Belts can be found within Jupiter’s magnetosphere too. But are the mechanisms energizing these particles the same for both planets? New research suggests that the magnetospheres of Jupiter and Earth may have more in common than previously thought…

As previously reported on Universe Today, there is a possible source to the magnetospheric “hiss” that energizes protons and electrons within the Earth’s Van Allen Belts. The discovery that low frequency “chorus” waves propagating through the upper atmosphere evolve into waves that can interact with charged particles is significant in that it helps to solve a 40 year debate as to where these waves come from. Now, the nature of Jupiter’s highly energetic particles trapped in its strong magnetic field has been brought into question.

The Galileo spacecraft (pictured) measured radio wave activity inside the magnetosphere as it orbited the gas giant over eight years. According to the scientific collaboration including researchers at the British Antarctic Survey (BAS), University of California, Los Angeles (UCLA), and the University of Iowa (UI), similar low frequency radio waves may be responsible for electron energization in the Jovian high energy particle belts as in the terrestrial Van Allen Belts.

Although details on the source of Earth’s “chorus” waves are sketchy (we know they originate outside of the plasmasphere surrounding Earth and evolve into a radio wave “hiss” inside the Van Allen Belts), the source of low frequency radio waves around Jupiter comes from the interactions between the moon Io and the Jovian magnetic field.

“On Jupiter, the waves are powered by energy from volcanoes on the moon Io, combined with the planet’s rapid rotation – once every 10 hours. Volcanic gasses are ionized and flung out away from the planet by centrifugal force. This material is replaced by an inward flow of particles that excite the waves that in turn accelerate the electrons.” – Dr Richard Horne, lead author of research, British Antarctic Survey (BAS).

The interaction of Jupiter’s moons with its atmosphere is highlighted when analysing the pattern of the polar auroral regions on the planet. As the magnetic field is so strong on Jupiter, massive regions of bright emission can be seen in the UV wavelengths (pictured top). This is emission from huge auroral displays as highly energetic particles funnel down magnetic flux and interact with Jupiter’s atmosphere (similar to Earth’s auroral displays, only much bigger). There are some strange patterns in the auroral “crown” – “footprints” of the Jovian moons, Io, Ganymede and Europa. The moons emit particles which get directed down to Jupiter by the gas giant’s magnetic field. These footprints appear as little spots in Jovian polar regions, rotating with the moons as they pass through the magnetosphere.

By far the strongest influence on Jupiter’s magnetosphere, Io is constantly erupting with material, firing it through the Jovian magnetic field. Thanks to Galileo data, it appears this fast orbiting moon generates low frequency radio waves, driving the high energy particles trapped within Jupiter’s plasmasphere through wave-particle interactions.

“For more than 30 years it was thought that the electrons are accelerated as a result of transport towards Jupiter, but now we show that gyro-resonant wave acceleration is a very important step that acts in concert.” – Dr Horne

These results will have a huge impact on space weather forecasting. As the Sun erupts during periods of heightened solar activity (i.e. during “solar maximum”), the reaction of the Earth’s plasmasphere is critical to understanding the quantities of damaging high energy particles that may influence space missions, damaging satellites and causing harm to astronauts. Looking into Jupiter’s huge magnetosphere will aid understanding of our own magnetosphere, hopefully improving solar storm predictions.

Source: British Antarctic Survey

As a giant planet, Jupiter takes everything to the extreme. Even the weather. A ferocious storm raging across the cloud tops has surprised scientists: it’s churning up material that was deeper down in the planet’s atmosphere. And there’s evidence that the planet’s jet streams are generated by its own heat, and not just from the Sun.

Even in the smallest telescope, it’s easy to see the distinct atmospheric bands that stretch around the planet, like a series of stripes. The strongest winds on the planet are at Jupiter’s northern latitudes. Here the winds can howl at 600 km per hour (370 miles per hour).

But astronomers have always wondered what drives these storms? Is it energy from the Sun, or is the planet’s own heat that gets the powerful jet streams driving winds across Jupiter.

In March 2007, several telescopes captured a rare atmospheric eruption, where two brand new storms appeared in the planet’s cloud tops.

The event was so well recorded because it coincided with the New Horizons spacecraft’s flyby with Jupiter. Many telescopes, including Hubble, NASA’s Infrared Telescope Facility, and a network of smaller telescopes around the world were making support observations of Jupiter.

An international team coordinated by Agustín Sánchez-Lavega from the Universidad del País Vasco in Spain presented their findings about this event in the January 24 issue of the journal Nature.

“Fortuitously, we captured the onset of the disturbance with Hubble, while monitoring the planet to support the New Horizons flyby observations of Jupiter in its route to Pluto. We saw the storm grow rapidly since its beginning, from about 400 kilometers [250 miles] to more than 2,000 kilometers [1,245 miles] in size in less than one day,” said Sánchez-Lavega.

With the storms, the researchers observed bright plumes of material. The newly forming storms pulled vast quantities of ammonia ice and water from deep below, and pushed it up 30 km (20 miles) above the cloud tops – higher than any other place on the planet.

By modeling the event, the researchers found that their observations supported the theory that Jupiter’s jet streams, which power the storm systems, come from much deeper inside the planet. Here on Earth, radiation from the Sun heats up the high atmosphere, and gets the jet streams going. But on Jupiter, it looks like the planet’s own heat drives these jet streams, and not the sunlight it receives.

Original Source: NASA/JPL News Release