Jupiter, king of the solar system, will get a new robotic visitor.
The Jupiter Icy Planet Explorer, or JOS, was launched Friday morning from the Guiana Space Center in Kourou, French Guiana, on the northeastern coast of South America. The original launch, scheduled for Thursday, was postponed after lightning was detected near the launch site.
The weather cleared on Friday and the spacecraft aboard the Ariane 5 rocket launched flawlessly. Half an hour later, Juice separated from the rocket’s second stage and embarked on its long journey.
Jupiter, the largest planet orbiting the sun, is charming in its own right, but its gigantic moons are the ultimate prize. Some are blocks of icy rock that may hide oceans harboring life beneath their surfaces. Juice, of the European Space Agency, or ESA, aims to closely study three of Jupiter’s moons: Callisto, Europa and Ganymede.
“This is one of the most exciting missions we’ve undertaken in the solar system, and by far the most complex,” said Josef Ashbacher, head of the European Space Agency.
The European spacecraft weighs six tons, and carries 10 advanced science instruments to study the moons and take pictures. Jupiter is not the primary target of the mission. Instead, it aims to explore Ganymede, the largest moon in the solar system, and two other moons, Europa and Callisto.
But getting to Jupiter will take more than eight years, with a series of gravitational twists or twists helping to bypass Venus, Mars and Earth to give the spacecraft the boost it will need to enter Jupiter’s orbit in July 2031.
When Juice finally reaches Jupiter, it will fly again and again through its three moons in a circular orbit, staying out of the giant planet’s dangerous radiation belts while collecting data. In total, 35 flybys are planned as spacecraft search for magnetic signals and other evidence to confirm the presence and size of oceans flowing beneath the moons’ surfaces. It will also track how the outer parts of the moons move in response to Jupiter’s gravitational pull, which is probably affected by the subterranean oceans.
A moon that might be promising in the search for life is Europa. Astronomers believe its surroundings are in direct contact with a rocky floor, which could provide food and energy for life as hydrothermal vents blast upwards. The juice will make two trips from Europa.
The spacecraft will also make 21 flybys of Callisto, which may also have a salty ocean but is thought to be less capable of supporting life.
But the primary goal of Juice’s mission is to study Ganymede, a moon so big it’s even bigger than the planet Mercury. The spacecraft’s trajectory around the Jovian system should allow the spacecraft to capture it into orbit around Ganymede in December 2034 – the first spacecraft to orbit a moon in the outer solar system. Starting at about 3,100 miles above the surface, the spacecraft’s altitude will be gradually reduced to just over 300 miles in 2035 — and possibly less, fuel permitting.
“If we have sufficient motivation, which means we made a good trip to Jupiter without too many problems, we would lower the orbit to an altitude of about 150 miles,” said Giuseppe Sarri, Juice project manager at the European Space Agency.
Orbiting Ganymede will allow scientists to understand the moon’s intricate features. It is the only moon in the solar system known to have its own magnetic field, possibly from a core of liquid iron like our planet. “If you were standing on the surface of Ganymede and you had a compass needle, it would point to the North Pole as it does on Earth,” said Michelle Dougherty of Imperial College London, who leads the magnetometer on Jos. “We want to understand why.”
The juicer should be able to discern the internal structure of the Ganymede, including the size and extent of its circumference. Rather, it should be able to measure the salt content of the ocean generated by the minerals dotting its interior, which can sustenance life. “We’re trying to understand where the salts came from,” noted Dr. Dougherty.
Ganymede’s ocean is vastly different from Europa’s, but it could still be habitable.
“For habitation, you need liquid water, a heat source, and organic materials,” said Dougherty. “If we affirm or deny these three things, we have done what we said we would do.”
The mission will end in late 2035 with a crash landing on the surface of Ganymede, unless a discovery made during the mission indicates that this could contaminate the lunar ocean.
What other missions will study Jupiter?
Juicing isn’t the only mission investigating Jupiter and its moons.
Juno, a NASA mission, has been orbiting Jupiter since 2016. Its focus has been on the planet itself rather than its moons, though it recently completed some close flybys of Europa and Ganymede, and soon will be moving away from volcanic Io.
But Juice is also expected to be eclipsed on Jupiter by another new NASA mission, the Europa Clipper, which will launch in October 2024. It is scheduled to reach the Jovian system in April 2030, due to its more powerful launch vehicle, SpaceX. Falcon. Heavy missile. But there is no competition. The two missions are meant to work together.
“There will be two spacecraft at the same time looking at Jupiter and its moons,” said Dr. Achbacher. “There is a lot of science to be gained from that.”
The two expeditions were born in 2008 in response to Exciting results from NASA’s Galileo spacecraftwhich orbited Jupiter from 1995 to 2003.
“Galileo found this very interesting magnetic signal that there is a conductive ice layer under Europa’s crust,” said Louise Brooker of the Johns Hopkins Applied Physics Laboratory, part of the Europa Clipper team.
Scientists now believe that this was a sign of a global ocean that included the interior of Europe.
Observations made by the Hubble Space Telescope in 2018 indicate that the moon Europa may occasionally erupt in its surroundings in plumes through cracks in its icy shell, at least 10 miles wide. This could provide a new way to study the ocean first-hand and look for signs of life while Clipper zips across the lunar surface, sometimes as low as about 15 miles.
“We’d probably fly through a plume,” said Dr. Brooker.
The results from Juice and Clipper will reveal whether a future mission, likely to Europa, should attempt to land on Jupiter’s moon to search directly for life in the ocean, something NASA has suggested. Such a mission may be two decades away, but its scientific value is enormous. Europe is interested in something similar, Dr. Achbacher said.
“We have discussed a mission to return a sample from one of the icy moons,” he said, which would bring the material back to Earth for closer study. “What we learn from Juice will be a very important contribution to that.”
Right now, the spotlight is on Juice’s, the first of a new era of spacecraft specifically designed for ocean-going on alien worlds. “I can’t wait,” said Dougherty. “This is the next step.”
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