Science

Juno to make closest approach to Solar System’s largest Moon, study Ganymede’s composition, ice shells

Since its arrival in Jupiter's orbit, the spacecraft is trying to understand the origin and evolution of the planet.

UPDATED: June 4, 2021 15:05 IST

The Juno spacecraft, which has been studying Jupiter since it reached the planet’s orbit in 2016 is all set for a historic flyby on June 7. The spacecraft will come within 1,038 kilometres of the surface of Jupiter’s largest moon, Ganymede. “The flyby will be the closest a spacecraft has come to the solar system’s largest natural satellite since Nasa’s Galileo spacecraft made its penultimate close approach back on May 20, 2000,” Nasa said in a statement.

During its close flyby, the spacecraft will send insights about the moon’s composition, ionosphere, magnetosphere, and ice shell, while its readings of the radiation environment near the moon will benefit future missions to the Jovian system. The flyby will help engineers understand and devise a new strategy for the Europa Clipper Mission, which will conduct a detailed survey of Jupiter’s moon Europa to determine whether the icy moon could harbour conditions suitable for life.

Juno, which has been making sweeping orbits around Jupiter, will begin collecting data about three hours before the spacecraft’s closest approach and peer into the Ganymede’s water-ice crust, obtaining data on its composition and temperature. The probe will use Ultraviolet Spectrograph (UVS) and Jovian Infrared Auroral Mapper (JIRAM) and Microwave Radiometer’s (MWR) for the studies during the close flyby.

Jupiter's moon IO cases a shadow on the planet. (Photo: Nasa)
Jupiter’s moon IO cases a shadow on the planet. (Photo: Nasa)

Studying largest Moon in Solar System

Jupiter’s moon Ganymede is bigger than the planet Mercury and is the only moon in the solar system with its own magnetosphere a bubble-shaped region of charged particles surrounding it. Its ice shell has some light and dark regions, suggesting that some areas may be pure ice while other areas contain dirty ice. Scientists hope that the MWR instrument will provide “the first in-depth investigation of how the composition and structure of the ice vary with depth, leading to a better understanding of how the ice shell forms and the ongoing processes that resurface the ice over time.”

According to Nasa, as Juno passes behind Ganymede, radio signals will pass through its ionosphere, causing small changes in the frequency that should be picked up by two antennas at the Deep Space Network’s Canberra complex in Australia. Measuring the changes will help understand the connection between Ganymede’s ionosphere, its intrinsic magnetic field, and Jupiter’s magnetosphere.

The spacecraft will be able to click several images during the flyby which is expected to last for 25 minutes. The JunoCam will capture images at a resolution equivalent to that from Voyager and Galileo probes that have passed through in the past. The team will then analyse the images, comparing them to those from previous missions, looking for changes in surface features that might have occurred over four decades.

What is Juno Spacecraft?

Named after Jupiter’s wife, the goddess Juno, the spacecraft was launched in 2011 and reached its destination in 2016. Since its arrival in Jupiter’s orbit, the spacecraft is trying to understand the origin and evolution of the planet by peering through its dense cloud cover. The spacecraft is investigating the existence of a solid planetary core, map Jupiter’s intense magnetic field, measure the amount of water and ammonia in the deep atmosphere, and observe the planet’s auroras.

Due to the speed of the flyby, the icy moon will from JunoCam’s viewpoint go from being a point of light to a viewable disk then back to a point of light in about 25 minutes. (Photo: Nasa)

Juno recently revealed for the first time the birth of auroral dawn storms the early morning brightening unique to Jupiter’s spectacular aurorae. Nasa had in January authorised a mission extension for the spacecraft, that will now continue its investigation of the solar system’s largest planet through September 2025, or until the spacecraft’s end of life.

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