Jupiter | Universe Today

Jupiter's two moons Ganymede and Callisto could be considered fraternal twins. They have a similar composition and size, but visually, they are different. Also, data from the Galileo and Voyager spacecraft reveal the two moons' interiors are very dissimilar, as well. The reasons for the differences have eluded scientists for 30 years, but a new study provides an explanation. During the Late Heavy Bombardment, Callisto escaped relatively unscathed, while Ganymede was a battered child; so much so that the later moon melted. "Impacts during this period melted Ganymede so thoroughly and deeply that the heat could not be quickly removed," said Dr. Amy Barr of the Southwest Research Institute. "All of Ganymede's rock sank to its center the same way that all the chocolate chips sink to the bottom of a melted carton of ice cream. Callisto received fewer impacts at lower velocities and avoided complete melting."
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We live in a cosmic shooting gallery. In Phil Plait's Death From the Skies, he lays out the dangers of a massive impact: destructive shockwaves, tsunamis, flash fires, atmospheric darkening…. The scenario isn't pretty should a big one come our way. Fortunately, we may have a silent guardian: Jupiter.

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Even though most of us have been suffering from poor seeing conditions due to both hemisphere's seasonal climate changes, the changes we're experiencing look like nothing compared to what's happening on Jupiter. If you think we've got turbulent atmosphere and more than our fair share of clouds – then check out what John Chumack's been watching! Read more…

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Scientists use crater distributions to tell the ages of planetary surfaces on rocky bodies. But how can the ages of gas planets be determined? Believe it or not, possibly from craters. Scientists from the National Institute of Astrophysics in Rome say that crater patterns on the two largest asteroids in the asteroid belt, Vesta and Ceres, could help pinpoint when Jupiter began to form during the evolution of the early Solar System. Their study modeling the cratering history of the two asteroids – which are believed to be among the oldest in the Solar System — indicates that the type and distribution of craters would show marked changes at different stages of Jupiter’s development.
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You've all heard me talk about watching the Moon occult a bright star. That's when we get a great example of stellar parallax from our Earthly viewpoint! But did you know that there are several other heavenly bodies that can cause an occultation that's easy to view through an amateur telescope if you just know when and where to look? Then let's take this opportunity to check it out… Read more…

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Have you stayed up late and observed the Jupiter impact site? Then don't be goofing around. Not since July 16-22, 1994 when comet Shoemaker-Levy crashed into Jupiter's southern hemisphere have amateur astronomers had the opportunity to witness history firsthand! What makes me think that you can do it? Because I have… Read more…

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Are you ready to stay up a little late and see if you can catch the new dark spot on Jupiter from what could have either been an asteroid or comet impact? It happened somewhere between July 17th and 19th and the scar is still fresh and visible. However, there is just a little bit you need to know to make your viewing the Jupiter impact through your telescope a success. Read more…

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After getting whacked unexpectedly by a small comet or asteroid, Jupiter is sporting a "bruise," which has been big news this week. In visible wavelengths, the impact site appears as a black spot. But in a new image taken in near infrared by the Gemini North telescope on Mauna Kea, Hawai'i, the spot shows up in spectacular glowing yellow.

"We utilized the powerful mid-infrared capabilities of the Gemini telescope to record the impact's effect on Jupiter's upper atmosphere," said Imke de Pater from the University of California, Berkeley. "At these wavelengths we receive thermal radiation (heat) from the planet's upper atmosphere. The impact site is clearly much warmer than its surroundings, as shown by our image taken at an infrared wavelength of 18 microns."
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As we reported yesterday, an amateur astronomer snapped evidence of an impact on Jupiter. Now, NASA has confirmed the black spot on the giant gas planet is in fact an impact and not just a weather-related disturbance. And Anthony Wesley has now made the biggest observation of his life.

"It still feels very surreal right now," he told Universe Today. "I guess it will take some time to really sink in (pun intended). I guess it shows that persistence and many hours at the scope eventually pays off."
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Amateur astronomer Anthony Wesley from Canberra, Australia captured an image of Jupiter on July 19 showing a possible new impact site. Anthony's image shows a new dark spot in the South Polar Region of Jupiter, at approximately 216° longitude in System 2. It looks very similar to the impact marks made on Jupiter when comet Shoemaker-Levy 9 crashed into the gas giant in 1994. (But read the Bad Astronomer's post that the black spot could also be weather.)
UPDATE (7/20): It has been confirmed this is an impact on Jupiter. Mike Salway shared the news Glenn Orton from JPL has imaged the Jupiter black spot with the NASA Infrared Telescope and he has confirmed it's an impact.

The list below shows the times (in UT) when the black spot will be visible again (generated in WinJupos by Hans-Joerg Mettig), and found on the Mike Salway's Ice In Space website.
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Io may be close to thermal equilibrium, according to a study published this week in Nature. And if the new findings are correct, the volcanically wild moon could one day break free of Jupiter's hold — and lose its rare, volcanic splendor.

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When Mars and Jupiter migrated to their present orbits around 4 billion years ago, they left scars in the asteroid belt that are still visible today.

The evidence is unveiled in a new paper in this week's issue of the journal Nature, by planetary scientists David Minton and Renu Malhotra from the University of Arizona in Tucson.  

The asteroid belt has long been known to harbor gaps, called Kirkwood gaps, in distinct locations. Some of these gaps correspond to unstable zones, where the modern-day gravitational influence of Jupiter and Saturn eject asteroids. But for the first time, Minton and Malhotra have noticed that some clearings don't fit the bill.

"What we found was that many regions are depleted in asteroids relative to other regions, not just in the previously known Kirkwood gaps that are explained by the current planetary orbits," Minton wrote in an email. In an editorial accompanying the paper, author Kevin Walsh added, "Qualitatively, it looks as if a snow plough were driven through the main asteroid belt, kicking out asteroids along the way and slowing to a stop at the inner edge of the belt." 

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NASA's Hubble Space Telescope has caught Jupiter's moon Ganymede playing a game of hide-and-seek. In this crisp Hubble image, Ganymede is shown just before it hides behind the giant planet. Images like this one are not only gorgeous and enjoyable to look at, but are also useful for studying Jupiter's upper atmosphere. As Ganymede passes behind the giant planet, it reflects sunlight, which then passes through Jupiter's atmosphere. Imprinted on that light is information about the gas giant's atmosphere, which yields clues about the properties of Jupiter's high-altitude haze above the cloud tops. And because Hubble's view is so sharp, we can learn more about Ganymede as well. Visible are several features on the moon's surface, most notably the white impact crater, Tros, and its system of rays, bright streaks of material blasted from the crater. Tros and its ray system are roughly the width of Arizona. Hubble has amazing eyesight!

And there's a movie, too!

More about Ganymede and Jupiter…
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Jupiter has a rocky core that is more than twice as large as previously thought, according to computer calculations by a geophysicist who simulated conditions inside the planet on the scale of individual hydrogen and helium atoms. "Our simulations show there is a big rocky object in the center surrounded by an ice layer and hardly any ice elsewhere in the planet," said Burkhard Militzer from University of California, Berkeley. "This is a very different result for the interior structure of Jupiter than other recent models, which predict a relatively small or hardly any core and a mixture of ices throughout the atmosphere." A comparison of this model with the planet's known mass, radius, surface temperature, gravity and equatorial bulge implies that Jupiter's core is an Earth-like rock 14 to 18 times the mass of Earth, or about one-twentieth of Jupiter's total mass, Militzer said. Previous models predicted a much smaller core of only 7 Earth masses, or no core at all.
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NASA has decided to return to Jupiter with a mission to conduct an unprecedented, in-depth study of the largest planet in our solar system. The mission is called Juno, and it will be the first in which a spacecraft is placed in a highly elliptical polar orbit around the giant planet to understand its formation, evolution and structure. Missions to Jupiter have been on again, off again, with a mission to Europa falling during the 2006 budget cuts, and the Jupiter Icy Moons Orbiter (which would have used a nuclear reactor to power an ion engine to send an orbiter to 3 of Jupiter's moons) getting the ax in 2005. Juno has been on the table since 2004, surviving budget cuts, although the mission has experienced delays. But it looks official now, and the spacecraft is scheduled to launch in August 2011, reaching Jupiter in 2016.
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