From the data collected by the probe, scientists deduce that Ganymede experienced a large impact millions of years ago, and the impact of this impact on Ganymede is profound.
Billions of years ago, the planetary-sized Moon of Jupiter suffered a major impact: a closer look at the data sent back by the probe as it flew past Ganymede, scientists estimate that Ganymede was hit by a 300-kilometer-diameter object.
It was a catastrophic event, and even the nightmare of extinction was not enough to describe its power. Everything within a thousand kilometers of the diameter of the impact point was melted, and the entire surface of the satellite was severely affected. Even the interior of the satellite has changed dramatically as a result. A similar event on Earth would directly wipe out all life on the planet. And if it happens on a satellite, it must be the end of the world.
Ganymede is one of Jupiter's four largest moons, and in fact, it is also the largest moon in the entire solar system, even larger than Mercury. With a diameter of 5,260 km, Ganymede is the ninth known object in the solar system.
In 1610, Galileo discovered Ganymede; in the early 1970s, spacecraft (Pioneers 10 and 11) made their first visit; and Voyager 1 and 2, which visited in 1979, gave us a closer look at Ganymede. Ganymede has two main surface features, which we call dark and bright zones. Dark zones are older (this is determined by the number of impact craters, with older surface features having more impact craters), while bright zones form later. About a third of Ganymede's surface is dark.
Above, Jupiter's moon, Europa, shows its dark and bright regions; grooves can be seen in the dark areas of the upper right. Image credit: NASA/Caltech Jet Propulsion Laboratory/Emily Lakdawala
In these dark areas there are grooves and long grooves, which at first glance appear to consist of a series of parallel lines. But if you take a step back, you can see that they cover most of Ganymede's surface in the shape of concentric circles. At first, it was thought that they covered only one hemisphere of Ganymede, but the latest research by scientists shows that they basically cover the entire ganymede, revealing a series of huge concentric features.
The center of these concentrated trenches is located about 20 degrees south of The Ganymede equator, exactly in the middle of the hemisphere (180 degrees west longitude) where Ganymede always turns its back to Jupiter, and this hemisphere is called the dorsal surface, and Ganymede's rotation time is consistent with its orbit around Jupiter, so it always maintains the same side toward Jupiter, as is the case with the Moon and Earth.
This strongly suggests that these grooves all have a common origin – a huge impact. It is difficult to say how big the impact craters formed after the impact were, but the impact was so large that no edges or recognizable craters were found. This makes the size of the impactor difficult to judge, but through some basic assumptions, scientists estimate that the diameter of the impactor is about 300 kilometers, crashing into Ganymede at a speed of about 20 kilometers per second.
The energy generated by the impact is beyond my brain's imagination. This is equivalent to a trillion million-ton bombs detonating at the same time. That's hundreds of millions of times the combined equivalent of all nuclear weapons on Earth. Wow!
By the way, the asteroid that slammed into the Gulf of Mexico and killed (non-birds and marines) dinosaurs was about 10 kilometers in diameter. That is, the asteroid that struck Ganymede was thirty times the diameter of the former and 27,000 times the volume of the former. Oh my goodness!
The image above shows the size of Earth (right), Ganymede (center), and Titan (left, replacing the asteroid that hit Ganymede).
Image credit: NASA/National Oceanic and Atmospheric Administration/Deep Space Climate Observatory, NASA/Caltech Jet Propulsion Laboratory/Emily Lakdawala, NASA/Jet Propulsion Laboratory/Space Science Institute/Goldan Ugarkovich
The impact was so great that scientists could not confirm whether the impact point was directly opposite Ganymede at 20° W and 180° W – or 20° N and 0° East. Both points coincide with the direction of the groove, but the former is more likely because the groove on Ganymede's side is more pronounced.
The impact released enormous heat to Ganymede. Interestingly, it has been discovered that there may be an ocean of liquid water deep below Ganymede's surface; I wonder if the impact is related to this. Radioactive material from the star's nucleus and tidal heat from Jupiter may help Maintain Temperature deep within Europa's surface, but an impact of this magnitude could also affect the temperature of The entire Ganymede.
Scientists have noticed that an impact of this magnitude will leave a large amount of material at the point of impact. Ganymede's gravity at that point also increases as a result. This is measurable. Future space probes, such as Jupiter's Ice Moon Explorer (JUpiter ICy moons Explorer) or Europa Clipper, may fly over Ganymede multiple times, allowing scientists to map Ganymede's gravitational field. If they could find a large amount of material left behind by the impact at the point of impact, that would be nice.
The largest known impact in the solar system has only now been discovered, which is interesting to say, and indeed makes sense. The force of the impact is so great that the light cannot see the power of the impact from one point, just as when standing on the surface of the earth, you cannot see that the earth is such a huge sphere. Evidence of the impact can only be found if Ganymede's global map is drawn.
At the beginning of the birth of the solar system, this magnitude of impact, can not be said to be common, but at least not unheard of. Fortunately, this is extremely rare today. But they did participate in shaping the world we see today, and we're trying to study them.
BY: Phil Plait
FY: Hairpin flower sweet bean
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