Spaceflight Insider

Juno solves lightning mystery, gets mission extension

Juno arrived in orbit above Jupiter on July 4, 2016. Since that time, the spacecraft has revolutionized humanity's knowledge of the gas giant. Image Credit: James Vaughan / SpaceFlight Insider

Juno arrived in orbit above Jupiter on July 4, 2016. Since that time, the spacecraft has revolutionized humanity’s knowledge of the gas giant. Image Credit: James Vaughan / SpaceFlight Insider

NASA’s Juno probe, which has been in orbit around Jupiter since July, 2016 has provided scientists at the Jet Propulsion Laboratory (JPL) opportunities for research. One such research paper, recently published in Nature, helps explain the nature of Jupiter’s polar lightning.

Until now, all science instruments that have traveled to Jupiter (Voyager 1, Voyager 2, Galileo and Cassini) have only looked at the Jovian lightning in the visible spectrum. Juno, however carries onboard the Microwave Radiometer Instrument (MWR). This device records a wide range of frequencies allowing scientists to have a better understanding of what is happening at Jupiter.

“No matter what planet you’re on, lightning bolts act like radio transmitters — sending out radio waves when they flash across a sky. But until Juno, all the lightning signals recorded by spacecraft (Voyagers 1 and 2, Galileo, Cassini) were limited to either visual detections or from the kilohertz range of the radio spectrum, despite a search for signals in the megahertz range. Many theories were offered up to explain it, but no one theory could ever get traction as the answer,” said Shannon Brown of NASA’s Jet Propulsion Laboratory in Pasadena via a company-issued release.

Brown, a Juno scientist and the lead author of the paper, went on, noting that, “In the data from our first eight flybys, Juno’s MWR detected 377 lightning discharges. They were recorded in the megahertz as well as gigahertz range, which is what you can find with terrestrial lightning emissions. We think the reason we are the only ones who can see it is because Juno is flying closer to the lighting than ever before, and we are searching at a radio frequency that passes easily through Jupiter’s ionosphere.”

Artist impression of lightning in Jupiter’s northern hemisphere. Information from the Juno spacecraft suggest a majority of the lightning activity on the gas giant is near its poles. Image Credit: NASA/JPL-Caltech/SwRI/JunoCam

Artist impression of lightning in Jupiter’s northern hemisphere. Information from the Juno spacecraft suggest a majority of the lightning activity on the gas giant is near its poles.
Image Credit: NASA/JPL-Caltech/SwRI/JunoCam

Lighting on Jupiter is analogous to the lighting of Earth. Both are generated by heat. At Jupiter, the light reaching the planet is 25 times dimmer than what we see here on Earth. Earth has a lot of atmospheric convection at the equator courtesy of the Sun. That churning creates the instability in the atmosphere that results in lighting. Unlike Earth, Jupiter gets most of its heat convection from the planet itself. The Sun provides just enough heat to help stabilize the Jovian equator. This moves the churning effects to the poles of Jupiter where lightning is most prevalent.

“These findings could help to improve our understanding of the composition, circulation and energy flows on Jupiter,” said Brown. But another question looms, she said. “Even though we see lightning near both poles, why is it mostly recorded at Jupiter’s north pole?”

In addition to Brown’s work, another paper from Ivana Kolmašová of the Czech Academy of Sciences, Prague, and colleagues published in Nature Astronomy presents the largest database to date of whistlers, lightning-generated low-frequency radio emissions around Jupiter. The data set is almost 10 times the size of that collected during the Voyager 1 flyby. A peak rate of four lighting strikes per second is six times higher than the peak values detected by Voyager 1. This is similar to the rate seen here on Earth.

“These discoveries could only happen with Juno,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute, San Antonio. “Our unique orbit allows our spacecraft to fly closer to Jupiter than any other spacecraft in history, so the signal strength of what the planet is radiating out is a thousand times stronger. Also, our microwave and plasma wave instruments are state-of-the-art, allowing us to pick out even weak lightning signals from the cacophony of radio emissions from Jupiter. “

More data about Jupiter’s lightning is scheduled to be collected during the thirteenth science flyby slated to take place on July 16.

The Juno program continued to receive good news as NASA announced the mission would be extended through 2022. The spacecraft’s primary mission should draw to a close in 2021. However, data collection and mission closeout should continue into the 2022 time frame. This extends the spacecraft’s time on orbit to an additional 41 months.

 “With these funds, not only can the Juno team continue to answer long-standing questions about Jupiter that first fueled this exciting mission, but they’ll also investigate new scientific puzzles motivated by their discoveries thus far,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington. “With every additional orbit, both scientists and citizen scientists will help unveil new surprises about this distant world.”

“This is great news for planetary exploration as well as for the Juno team,” said Scott Bolton, “These updated plans for Juno will allow it to complete its primary science goals. As a bonus, the larger orbits allow us to further explore the far reaches of the Jovian magnetosphere — the region of space dominated by Jupiter’s magnetic field — including the far magnetotail, the southern magnetosphere, and the magnetospheric boundary region called the magnetopause. We have also found Jupiter’s radiation environment in this orbit to be less extreme than expected, which has been beneficial to not only our spacecraft, but our instruments and the continued quality of science data collected.”

Currently the Juno spacecraft is in a 53 day orbit as opposed the the planned 14 day orbital period. Concerns about Juno’s fuel system, namely valve operation, led to the change in the spacecraft’s primary orbit. While this change has slowed the gathering of scientific data, it does not appear to have had a major impact on the mission overall.

Juno is part of NASA’s New Frontiers Program, which is managed out of the space angecy’s Marshall Space Flight Center in Huntsville, Alabama, for NASA’s Science Mission Directorate. NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute in San Antonio.

 

 

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Joe Latrell is a life-long avid space enthusiast having created his own rocket company in Roswell, NM in addition to other consumer space endeavors. He continues to design, build and launch his own rockets and has a passion to see the next generation excited about the opportunities of space exploration. Joe lends his experiences from the corporate and small business arenas to organizations such as Teachers In Space, Inc. He is also actively engaged in his church investing his many skills to assist this and other non-profit endeavors.

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