On September 29, NASA’s Juno spacecraft captured excellent images of the frozen moon Europa as the solar-powered probe sped by at a relative rate of around 53,000 mph as it continued to collect additional science data during an extended mission around Jupiter (85,000 kilometres per hour).
Since NASA’s Galileo spacecraft sailed by Europa on January 3, 2000, Juno’s flyby was the closest one that a spacecraft has been to the moon’s icy surface. On September 29, Juno made a flyby of Europa at a distance of 218 miles.
The moon Europa is somewhat smaller than the Earth’s moon and is surrounded by a thick layer of ice on top of a potentially livable ocean of salty water. Europa Clipper is a NASA spacecraft that will be launched in 2024 on a mission to explore Jupiter’s frozen moon and look for signs that Europa may contain the building blocks for life.
After arriving at Jupiter in 2030, the Europa Clipper will conduct approximately 50 flybys of the icy moon, getting as close as 25 kilometres (16 miles) from Europa’s ice surface. On September 29, however, the Juno spacecraft had only two hours to collect data.
Juno was built to gather information about Jupiter by concentrating its scientific instruments on the atmosphere, magnetic field, and interior structure of the massive planet. After orbiting Jupiter on July 4, 2016, Juno became the first spacecraft to take pictures of the planet’s poles. The robotic mission was launched on an Atlas 5 rocket by United Launch Alliance from Cape Canaveral on August 5, 2011.
Early in 2021, NASA gave the Juno mission an extension, enabling the spacecraft to continue its research of the sun’s biggest planet through September 2025, assuming it doesn’t malfunction.
Over time, Juno’s trajectory is being affected by Jupiter’s uneven gravitational field, which is also tugging the closest point of the spacecraft’s extended orbit northward. The change in Juno’s orbit enables flybys of Ganymede, Europa, and Io, three of Jupiter’s largest moons, as well as a clearer view of the planet’s North Pole.
Juno passed Ganymede on June 7, 2021, and is scheduled to fly by Io twice on December 30, 2023, and February 3, 2024.
With each flyby, the spacecraft’s orbit gets a little bit closer. Last year, the gravitational force of Ganymede reduced Juno’s orbital period from 53 to 43 days, while the gravity of Europa condensed Juno’s orbit to 38 days. The Juno spacecraft will be dragged into a lower orbit with a period of 33 days by the Io flybys in 2023 and 2024.
According to Scott Bolton, the main investigator on Juno at the Southwest Research Institute in San Antonio, “Juno began off entirely focused on Jupiter.” The team is quite happy that we expanded our analysis to encompass three of the four Galilean satellites as well as Jupiter’s rings during our extended mission.
“With this flyby of Europa, Juno has now observed up close two of Jupiter’s most fascinating moons, and their ice shell crusts appear significantly distinct from one another. Io, the solar system’s most eruptive body, will join the group in 2023, according to a statement from Bolton.
A microwave radiometer for atmospheric soundings, ultraviolet and infrared spectrometers, particle detectors, a magnetometer, and an experiment with radio and plasma waves are among the nine scientific instruments on board Juno. The JunoCam colour camera on the Jupiter orbiter also gathers visual data for processing and analysis by a global army of citizen scientists.
The spacecraft’s other instruments were adjusted to search for particles lofted from Europa in potential eruptions through cracks in the moon’s global ice sheet when JunoCam took pictures of Europa during the flyby on September 29. The Hubble Space Telescope found evidence of ongoing eruptions from Europa.
The worldwide ice shell of Europa was anticipated to be measured in thickness by Juno’s microwave radiometer. Additionally, the spectrometers on board the spacecraft were tasked with mapping the amounts of water ice, carbon dioxide, and organic compounds over around 40% of Europa’s surface.
Candy Hansen, a co-investigator on the Juno mission and head of planning for the JunoCam camera at the Planetary Science Institute in Tucson, Arizona, explained that the science team will be comparing the entire set of images captured by Juno with images from earlier missions to determine whether Europa’s surface features have changed over the past two decades. The current geologic map will be completed with JunoCam photos, which will take the place of the region’s current low-resolution coverage.