A Spacecraft Orbiting Jupiter Intercepted FM Radio Emission From Its Largest Moon, Ganymede
For the first time in history, FM radio signals have been received from one of the ‘Galilean moons’ of Jupiter, Ganymede by Juno, the spacecraft that is orbiting the planet. However, the phenomenon did not occur because of some extra-terrestrial beings, but it occurred because of a scientific phenomenon.
Juno is a spacecraft that is orbiting Jupiter with a mission to understand and study the factors that led the planet to be evolved initially and to study its gravitational force, magnetic fields, other atmospheric measures and compositions, and its whole process of evolution.
Now, recently, Juno received some FM radio signals from Jupiter’s moon, Ganymede, for the first time in all these years, for a brief period of 5 seconds when the spacecraft was going at a speed of 50 km/second.
If it had been a movie, the scientists would have said that these signals are some way for extra-terrestrial beings to communicate with the people of Earth. But the reality is different. NASA’s ambassador Patrick Wiggins has clearly said that no aliens are involved behind these FM radio signals. In fact, it is all because of a natural scientific phenomenon.
Decametric Radio Emission
Somewhere around 1955, scientists accidentally discovered radio bursts emitting from Jupiter. They sought to understand what were the factors that were responsible for causing the emission of radio waves from the planet.
What they found was that these radio bursts were happening in tens of meters wavelength, and hence, they gave the phenomenon the name of Decametric radio emission. All these years, they collected radio data and all forms of information they could find about Jupiter, and through matching these radio bursts with the rotation of the planet, they finally discovered Jupiter’s magnetic field.
They studied the characteristics of these radio waves and realized that these waves can be polarized, as in grouped together, or completely unpolarized. Imagine them as ripples in water, or waves moving in a slithering manner as a snake does. Most of the radio waves from Jupiter were found to be polarized because these waves were emerging from a region where there is a magnetic field.
Now, when charged particles like protons and electrons pass through a magnetic field, their paths change, and they accelerate and start moving in spirals around this magnetic field towards either of the north or south poles. This accelerated ‘oscillatory’ movement of the charged particles is what causes the emission of radio waves, and its wavelength depends on the energy of the charged particles.
In Jupiter, the frequency of these waves increases in areas where the magnetic field is stronger. This radio emission is called cyclotron emission, and the radio noise that is heard from Jupiter is because of this cyclotron emission of electrons.
Radio waves from Jupiter never go above 40Mhz frequency.
The cause of Ganymede sending off radio signals is the same.
Juno was passing through one of the poles of Jupiter where magnetic lines connect to Ganymede. That was when it intercepted the radio signal. The electrons responsible for the generation of these radio signals also “caused auroras in the far-ultraviolet spectrum” and were caught on Juno’s camera.