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- How did the planet Mercury form?<\/strong> Scientists have been pondering this question for a long time.<\/li>\n
- According to new research, Mercury originated from the massive grazing collision<\/strong> of two similarly-sized bodies.<\/li>\n
- Collisions like this one were common in the early solar system<\/strong> billions of years ago. In fact, they likely accounted for about 1\/3 of all impacts.<\/li>\n<\/ul>\n
Mercury is the smallest and innermost planet in our solar system. It looks a lot like our moon at first glance, but it\u2019s its own world, with unique geology and history. Scientists have been trying to figure out how it formed for a long time. And now, a new study from researchers in Brazil, Germany and France has shed some new light on the question. In a new preprint paper published on March 4, 2025, they said that a grazing giant collision between two similar-sized rocky bodies likely created Mercury a few billion years ago.<\/p>\n
Mark Thompson wrote about the latest findings in Universe Today<\/em> on March 25, 2025.<\/p>\n
2025 EarthSky lunar calendar is available now. A unique and beautiful poster-sized calendar with phases of the moon for every night of the year. Get yours today!<\/p>\n
How did Mercury form?<\/h3>\n
Despite its superficial resemblance to our moon, Mercury is a unique and strange world. Researchers have found evidence for a possible 10-mile thick layer of diamonds between the core and mantle of this planet, along with salty glaciers that could even be habitable.<\/p>\n
And until now, scientists haven\u2019t fully understood how Mercury formed. Surrounding its iron core is a relatively thin silicate mantle. In fact, the solid inner core and the molten outer core together take up nearly 85% of the planet\u2019s radius. That\u2019s much more than any of the other rocky planets. This posed a mystery. As the paper states:<\/p>\n
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The origin of Mercury still remains poorly understood compared to the other rocky planets of the solar system. One of the most relevant constraints that any formation model has to fulfill refers to its internal structure, with a predominant iron core covered by a thin silicate layer.<\/p>\n<\/blockquote>\n
![\"Cutaway](\"https:\/\/earthsky.org\/upl\/2025\/03\/Mercury-interior-diagram-April-17-2019.png.jpeg\")
View larger. | Diagram depicting the interior structure of Mercury as currently understood. The overall core is nearly 85% of the planet\u2019s radius, much more than other rocky planets in our solar system. This supports the theory that Mercury formed from the grazing impact of 2 similarly-sized bodies. Image via NASA\/ Goddard Space Flight Center.<\/figcaption><\/figure>\n Collisions in the early solar system<\/h3>\n
The early solar system was a chaotic place, with frequent collisions between rocky bodies. And Mercury\u2019s strangely large core has led scientists to hypothesise that a collision with a much larger body might have stripped away its outer layers. <\/p>\n
But simulations of the early solar system have found collisions between very differently sized objects to be relatively rare. On the other hand, recent simulations suggest that collisions between very similarly sized bodies are much more common. In fact, they likely accounted for about 1\/3 of all impacts in the early solar system. And this, the new study says, is how Mercury likely formed.<\/p>\n
![\"Black](\"https:\/\/earthsky.org\/upl\/2023\/06\/BepiColombo_Mercury_flyby_middle-ESA-800x655.png\")
One of the newest images of Mercury, from the 3rd flyby of the BepiColombo spacecraft on June 19, 2023. Image via ESA\/ BepiColombo\/ MTM.<\/figcaption><\/figure>\n Did a massive collision create Mercury?<\/h3>\n
Patrick Franco at the National Observatory in Brazil led the new study into whether two similar-sized rocky bodies could form a planet similar to Mercury.<\/p>\n
Their study used a main body \u2013 a proto-Mercury \u2013 with a mass just over 10% of Earth\u2019s, and a 30% iron makeup. In the simulations, the researchers experimented with variously sized secondary bodies, with varying amounts of iron.<\/p>\n
They also varied the impact velocities between the two bodies, from 2.8 to 3.8 times the mutual escape velocity. The escape velocity is the minimum speed needed for an object to escape the orbit of or contact with a primary body.<\/p>\n
Within these parameters, the researchers experimented with collision scenarios that could have occurred billions of years ago in the early solar system.<\/p>\n
And they eventually found a scenario that produced a planet that matched Mercury\u2019s mass with a 5% margin. And its core was 65-75% iron, compared to Mercury\u2019s current value of 70%. It\u2019s strong evidence, they said, that Mercury formed from a grazing collision between two similarly sized rocky bodies.<\/p>\n
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Forming Mercury by a grazing giant collision involving similar mass bodies. Patrick Franco et. al. <\/p>\n
\u2014 AstroArxiv (@astroarxiv.bsky.social) 2025-03-05T05:07:08.122613+00:00<\/p>\n<\/blockquote>\n
![\"Smiling](\"https:\/\/earthsky.org\/upl\/2025\/03\/Patrick-Franco-National-Observatory.jpeg\")
Patrick Franco at the National Observatory in Brazil is the lead author of the new Mercury study. Image via LinkedIn.<\/figcaption><\/figure>\n Bottom line: A new study says Mercury was formed from a huge collision between 2 similarly-sized rocky bodies.<\/p>\n
Source: Forming Mercury by a grazing giant collision involving similar mass bodies<\/p>\n
Via Universe Today<\/p>\n
Read more: Mercury may have a 10-mile-thick layer of diamonds<\/p>\n
Read more: Mercury images from final flyby of BepiColombo!<\/p>\n
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\n - According to new research, Mercury originated from the massive grazing collision<\/strong> of two similarly-sized bodies.<\/li>\n