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The thought of an asteroid impact is scary enough, let alone witnessing one. One such impact killed the dinosaurs 65 million years ago, and now it seems another space rock had a dramatic effect on the solar system's largest moon. 

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A study has found that an asteroid 20 times larger than the one that wiped off dinosaurs from the face of Earth struck Jupiter's moon Ganymede some four billion years ago. The strike shifted the moon's axis.

Scientists have known for a long time that Ganymede was once hit by a massive asteroid that resulted in the formation of concentric circles around a specific point on its surface. 

"These giant impacts are believed to have been frequent in the early solar system," planetologist Hirata Naoyuki from Kobe University told Newsweek. 

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He added that the impact affected the interior structure of Ganymede "significantly". This is clear from the size of the transient crater as it makes up for 25 per cent of the size of Ganymede.

The study has been published in the journal Scientific Reports. Hirata studied the moon and realised that the site where the crater exists is almost exactly on the meridian opposite Jupiter. He concluded that the impact was so powerful that it shifted Ganymede's rotational axis. 

Something similar happened to Pluto following an asteroid impact, the New Horizons space probe had revealed.

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Simulations on the impact event showed that the asteroid that led to this dramatic reorientation was likely approximately 190 miles in diameter. This is 20 times more than the one that hit Earth 65 million years ago. 

JUICE to study Ganymede

Ganymede hosts subsurface oceans and has been a likely candidate in the hunt for livable space bodies. Probes to study the moon further are in the pipeline. In 2015, the Hubble Space Telescope found evidence that Ganymede hosts an underground saltwater ocean 60 miles deep, almost 10 times deeper than the oceans on our planet.

The European Space Agency's JUICE space probe is also on its way to Ganymede, arriving its orbit in 2034. It will also study Callisto and Europa, Jupiter's other two icy moons.