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Space Topics: New HorizonsMission Update: Results from Jupiter Encounter Streaming In
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New Horizons Artist's conception of the New Horizons spacecraft at Pluto and Charon. Created: 2004. Credit: JHUAPL / SwRI |
May 3, 2007:
Out in the vast emptiness of space, beyond the orbits of Mars and Jupiter, New Horizons is racing towards the edge of the solar system at over 50,000 miles per hour, 20 times faster than a speeding bullet. Two months ago, on February 27, the spacecraft passed within 1.4 million miles of giant Jupiter, an encounter that lent the spacecraft a valuable gravity assist on its way to Pluto and the Kuiper belt. The encounter also provided the New Horizons team with a unique opportunity to test the capabilities of the spacecraft and its operators under real fly-by conditions. “The Jupiter flyby was a stress test for of our spacecraft and team” said Alan Stern, the mission’s Principal Investigator who is also Associate Administrator of NASA’s Science Mission Directorate. “Both passed with flying colors.”
In some ways the Jupiter encounter was even more demanding for New Horizons than the Pluto flyby that will take place in the summer of 2015. For one thing the 700 separate observations the spacecraft made of Jupiter are more than double the number that are planned for the Pluto system. For another, said Stern, the instruments aboard New Horizons were not designed for the conditions on Jupiter but for those that prevail near Pluto, where the sun is 1000 times dimmer than it is on Earth. As a result, the objects in the Jovian system were too bright for New Horizons’ instruments to make full use of their capabilities. In effect, explained Stern, “the instruments were operating with one hand tied behind their back.”
Even under these difficult conditions New Horizons gathered volumes of data during its fly-by, which are both visually stunning and rich in scientific import. The data was initially stored in on-board memory banks, and is currently being transmitted to Earth in a steady stream. Around 34 gigabits of information were gathered by the spacecraft at Jupiter, and their transmission to Earth will continue for several more weeks. Nevertheless, with 70% of the data now hand, Stern and his team took the time to point out some of New Horizons’ remarkable observations from the Jupiter encounter.
Jupiter's "Little Red Spot" as Viewed from New Horizons and the Hubble Space Telescope The black and white image of Jupiter's Little Red Spot was captured by New Horizon's LORRI instrument on February 27, 2007, from a distance of 3 million kilometers (1.9 million miles). The superimposed color is from an image taken at the same time by the Hubble Space Telescope's Wide Field Planetary Camera from a distance of 800 million kilometers (500 million miles). Credit: NASA/JHUAPL/SwRI |
One of the images that stands out for its clarity and beauty is a close-up of Jupiter’s Little Red Spot (LRS) – a giant hurricane-like storm, about 70% the size of the Earth. Unlike its counterpart, the famous Great Red Spot, which is twice as large and has been in place for centuries, the LRS is a relative newcomer. In the late 1990’s three separate storms that had been in place for the last 40 years joined together to form a single giant storm. Then, around two years ago, the “super storm” began turning red, forming what is now known as the LRS. Scientists aren’t sure why the storms are turning red, but they speculate that the atmospheric disturbance is stirring up sulphur-bearing droplets from deep within the planet. Aided by the extremely detailed images from New Horizons’ LORRI instrument, they hope to get some more definite answers about the composition and dynamics of Jupiter’s giant red storms.
“This is our best look ever of a storm like this in its infancy,” said Hal Weaver of the Johns Hopkins University Applied Physics Laboratory(APL), who is New Horizons’ project scientist. “Combined with data from telescopes on and around Earth taken at the same time New Horizons sped past Jupiter, we’re getting an incredible look at the dynamics of weather on giant planets.”
Another major target of the New Horizons fly-by was the Jovian moon Io – the most volcanically active body in the solar system. Io’s surface is constantly made and remade by the lava flows from hundreds of volcanoes, both old and new. The spacecraft’s Ralph imager produced a full map of the moon’s surface which will enable scientists to determine how it has changed since Cassini flew by in 2000. Ralph was also measuring the temperatures of the different lava flows, providing scientists with important clues on their composition.
Tvashtar erupts on Io A giant plume, 330 kilometers high, rises above the volcano Tvashtar on Io. The sunlit side of the Jovian moon is deliberately overexposed to bring out the details inthe plume. The image was taken by New Horizons' LORRI instrument on March 1, 2007, from a distance of 2.3 million kilometers. Credit: NASA/JHUAPL/SwRI |
But the most spectacular images of Io were undoubtedly those that showed a giant volcanic plume rising 330 kilometers (200 miles) above the erupting volcano Tvashtar. The images, taken from a distance of 2.3 million kilometers (1.4 million miles) show the plume as a giant dome-like bubble above the surface of Io, and at its heart a brilliant point of light marking the location of the glowing erupting lava. “Galileo orbited Jupiter for 6 years and never saw a plume like that” said John Spencer of the Southwest research Institute, deputy leader of the mission’s Jupiter Encounter Science Team, marveling at New Horizons’ good fortune. “We just happened to breeze by, and there it is!”
New Horizons’ remarkable sense of timing appeared to hold true for other observations as well. One of the spacecraft’s main goals during the fly-by was to observe Jupiter’s thin rings which, like Saturn’s far more spectacular ones, are composed of particles of dust, ice, and debris. Scientists had hoped that a close inspection of the system will reveal tiny moons orbiting inside the rings, replenishing their store of particles and shepherding them along in their orbits. Two such moons are already known, Metis and Adrastea, each only tens of kilometers in diameter, but scientists suspect there are more. Without them, the rings would surely dissipate very quickly.
Clumps following Adrastea Three clumps in Jupiter's main rings following the tiny moon Adrastea (16 kilometers in diameter). The clumps most likely formed as a result of the impact of a Jupiter-family comet onto a large ring particle shortly before New Horizons arrived in the Jupiter system. Credit: NASA / JHUAPL / SwRI |
As of now, the New Horizons team has not found any additional moons in the rings of Jupiter, though this does not mean that further study will not reveal some. In fact, a dark region in the midst of the the rings suggests the presence of a moon that had cleared a path for itself, and scientists will be looking closely for it. What they did find, however, were three large clumps of debris in the rings trailing behind the moon Adrastea like ducklings following their mother. The clumps are almost certainly debris from a collision between a massive object – possibly a Jupiter family comet – and a relatively large boulder in the rings. Such clumps however do not last long, a few months at the most, which means that event took place in the very recent past. “We almost saw a space collision” marveled Jeff Moore of NASA Ames, the Jupiter Encounter Science Team lead.
Altthough New Horizons swept by Jupiter over two months ago, it has not yet left the Jovian system behind. That is because it is still traveling down Jupiter’s “magnetotail” – a strip of magnetically-charged particles generated by the planet’s fierce magnetic field stretching out hundreds of millions of miles towards the orbit of Saturn. No other spacecraft has ever conducted such a prolonged and detailed observation of a planet’s magnetotail, and New Horizons will probably continue studying it for several more months. At some point the spacecraft will leave the magnetotail behind, but Stern and his colleagues can’t say for sure when that will happen. That is because much like tails of the more familiar variety, magnetotails tend to flap unexpectedly.
New Horizons holds a special place in the hearts of Planetary Society members. Time after time, when the mission to Pluto was on the budgetary chopping block, Planetary Society members mobilized, launching a grassroots campaign to save the mission. “The Society and its members played a key role in convincing NASA to compete and Congress to fund this mission" said Alan Stern in a statement. "The New Horizons team will forever owe a debt of thanks to The Planetary Society for their advocacy of the scientific exploration of the ninth planet and the ancient Kuiper Belt it resides in. "The Planetary Society and its members can take pride in their successful efforts to see this historic planetary exploration mission launched" Stern added. And as we watch the spacecraft race through space, performing flawlessly and providing a plethora of information on our solar system, we know that in no small part – we made it happen.
One of the most striking image to come out of New Horizons’ Jupiter encounter shows Europa, the smallest of Jupiter’s four Galilean moons, rising above the massive bulk of the giant planet. The image is of little scientific value in itself, but it does what few scientific discoveries can do: it reminds us that out in the vast emptiness that is space strange and wondrous worlds beckon to us, holding close their secrets.
Europa rises Credit: NASA / JHUAPL / SwRI |
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