Juno’s unprecedented views of Jupiter and its moons are a gift that keeps on giving.
The NASA spacecraft was originally slated to end its mission in 2018 after completing 34 orbits of the giant planet. It’s now on orbit 47. How long scientists will get this front-row view of these worlds isn’t clear, particularly as the spacecraft zooms ever closer to the gas giant and the powerful, destructive radiation of its magnetosphere.
But Juno is tough, said space physicist Scott Bolton, principal investigator for the Juno mission, at a December 14 news conference in Chicago at the American Geophysical Union’s fall meeting. The spacecraft “is built like an armored tank, and its shields are holding,” said Bolton, of the Southwest Research Institute, which has headquarters in San Antonio.
After entering a wide orbit around Jupiter in 2016, Juno’s images quickly began to help scientists peer into the planet’s mysteries, including a geometric array of cyclones around its poles and the strange, convoluted shape of its magnetic field (SN: 3/7/18; SN: 9/5/18). Juno spied lightning storms zipping across the tops of the planet’s clouds, and revealed that Jupiter is the only planet other than Earth known to host ephemeral, lightning-generated atmospheric glows known as sprites and elves (SN: 8/5/20; SN: 11/2/20).
Juno has also passed by some of the planet’s moons, flying by Ganymede in 2021. Ganymede “is bathed by Jupiter’s magnetic field,” and Juno was able to observe, among other things, a tug of war of magnetic field lines between the planet and its moon, said space physicist Thomas Great house, also of the Southwest Research Institute.
In September, Juno flew by Jupiter’s moon Europa, capturing in new detail the chaotic crisscrosses of cracks, ridges and bands in the moon’s icy surface. Now the spacecraft is on its way toward Io, the innermost moon.
While Juno seems to be going strong, “the end could come in two different ways,” Bolton said. Juno could become too degraded by the intense radiation to function — or it could simply run out of propellant, which is needed to keep its antennas pointed toward Earth. If that happens, “it could be collecting data, but can’t send it back.”
The NASA rover has witnessed dusty whirlwinds before. But when this one swept right over Perseverance, the rover’s microphone happened to be turned on. So the first-of-its-kind data include the sounds of dust grains either pinging off the microphone or being transmitted to the mic through the rover’s structure, researchers report December 13 in Nature Communications.
Because the rover’s microphone is turned on only occasionally, the team estimates that such events, when they occur, might be recorded just around 0.5 percent of the time.
Wind speeds in the walls of the dust devil reached nearly 40 kilometers per hour, planetary scientist Naomi Murdoch of the Institut Supérieur de l’Aéronautique et de l’Espace in Toulouse, France, and colleagues report. As with previous whirlwinds detected by other instruments, this late-morning dust devil caused a slight drop in atmospheric pressure and rise in temperature as it swept over the rover on September 27, 2021. It was 25 meters in diameter, at least 118 meters tall and ambled by at about 20 kilometers per hour.
One big surprise, Murdoch says, is that a prodigious amount of dust was airborne in the calm center of the whirlwind as well as in the brisk winds that formed its walls. Data from this event, as well as from other whirlwinds measured by the rover’s instruments, will help researchers better understand how dust gets lifted off the Martian surface
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