NASA just discovered something new in 20-year-old Galileo data

Mindy Sparks
May 2, 2018

Looking at the Galileo info again, scientists were able to paint a new picture of Ganymede that involves plasma rain falling on the moon's icy poles and "an explosive magnetic event" happening between Jupiter and Ganymede's magnetospheres.

The mission ended in 2003, but newly resurrected data from Galileos first flyby of Ganymede is yielding new insights about the moons environment - which is unlike any other in the solar system. It is thought to have a large subsurface ocean, sandwiched between two layers of ice and possibly containing more saltwater than all the water in Earth's oceans. The new results show fascinating facts about the magnetosphere's unique structure.

The orbiter arrived at Jupiter in 1995 and spent the next eight years studying the gas giant and its satellites.

This infographic describes Ganymede's magnetosphere.

"We are now coming back over 20 years later to take a new look at some of the data that was never published and finish the story. We found there's a whole piece no one knew about", Glyn Collinson from NASA's Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the paper, said in a statement Monday. The event saw plasma rain knock a barrage of high-energy particles onto Ganymede's icy surface. The interplay between the magnetic fields of the moon and its host planet also caused strong flows of plasms between them.

Now, NASA has done some scientific digging of its own into 20-year-old data from the Galileo satellite and uncovered new insights into Ganymede, Jupiter's uniquely magnetic moon.

The powerful solar wind doesn't affect Ganymede because it is cocooned within the larger magnetosphere of Jupiter.

"Studying magnetospheres throughout the Solar System not only helps us learn about the physical processes affecting this magnetic environment around Earth, it helps us understand the atmospheres around other potentially habitable worlds, both in our own Solar System and beyond".

Since Ganymede has a magnetosphere, it has auroras as well, and they are unusually bright.

In this illustration, the moon Ganymede orbits the giant planet Jupiter. Ganymede is depicted with auroras, which were observed by NASA's Hubble Space Telescope.

This event, known as a "magnetic reconnection", was caused by the tangling and snapping of magnetic field lines.

Astronomers believe the reconnection occurring as the two magnetic fields interact helps explain why the moon's auroras are so bright.

The auroras on Ganymede are similar to those we see here on Earth, but with one important difference: Earth's aurora's (or "Northern Lights") are caused by the flow of particles from the Sun, while those seen on Ganymede are are actually caused by Jupiter itself.

When analyzing the data, the team noticed that during its first Ganymede flyby, Galileo fortuitously crossed right over Ganymede's auroral regions, as evidenced by the ions it observed raining down onto the surface of the moon's polar cap.

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