Mysteries in the solar system are abundant. Although it sometimes looks like we have learned a lot, you can choose any object in the solar system and quickly ask yourself unanswered questions. This certainly applies to tiny mercury.
Mercury’s secret is in its core. Soil -based radio observations in the 1960s and 1970s showed that it had a massive core. The Mariner 10 mission in 1975, the first mission of Mercury, provided more precise measurements, and the Messenger mission from 2010 to 2015 provided the most convincing proof that the core of the planet is massive. For some reason, the tiny planet has a core that makes up about 70% of its mass. This is much larger than the core of the earth (30%) and the core of Mars (25%). This is sometimes referred to as a “mercury problem”.
Mercury has a diameter of around 2400 km and has a core of 1800 km. The earth has a diameter of around 12700 km and has a core of about 7000 km in diameter. Photo credits: left: NASA -APL/Right: From Isadoraofibiza – File: Earth Poster.svg, CC from 3.0, https://commons.wikimedia.org/w/index.php?curid=146405186
The most important working hypothesis for the Mercury problem says that the planet is a victim of a collision with an object of different sizes. The catastrophic collision stopped a large part of the coat and the crust of the planet and left only a thin crust and a coat over the solid core. Unfortunately, simulations show that collisions between bodies with very different masses were very rare.
New research in nature Astronomy says that a collision between mercury and another object is responsible for the unusual interior structure of Mercury, but the other object was not greater than mercury. It is entitled “Formation of mercury through a grazing giant collision with similar mass bodies”. The main author is Patrick Franco from Institut de Physique du Globe de Paris, Université Paris Cité, CNRS, Paris, France.
“The origin of mercury is still poorly understood compared to the other rocky planets of the solar system,” write Franco and his co-researchers. “To explain its internal structure, it is usually seen as a product of a huge influence. However, most studies take on a binary collision between bodies with significantly different masses, which seems unlikely according to N-body simulations.” One of the reasons for its rarity is that the impactor had to be in an extremely eccentric orbit before the effects, and that is rare.
The huge impact scenario suggests that an impact between a planetary embryo with 2.25 times the current mass of the mercury and a six-time object removes the coat of the embryo and what is left, the internal structure of Mercury is similar. But if these types were rare of non -matching collisions, what else could have happened?
Collisions between objects with similar masses were much more common in the young solar system after detailed numerical simulations. The researchers say that in contrast to the huge impact scenario, only a pasture with a similar mass object is required to explain mercury and its unusual interior structure.
“By simulation, we show that the formation of mercury does not require exceptional collisions. A pasture between two protoplanets of similar masses can explain its composition. This is a much more plausible scenario from a statistical and dynamic point of view,” said the main author Franco in a press release. “Our work is based on the determination, which was carried out in previous simulations that collisions between very unequal bodies are extremely rare events. Collisions between objects of similar masses are more common, and the aim of the study was to check whether these collisions are able to create a planet with the characteristics observed in Mercury.”
The early solar system was much more chaotic and chaotic than now. Rocky planetary embryos joked the position in the inner solar system and it was not clear which would finally be planned. In this environment, the collisions between similar mass objects were much more likely.
“They developed objects within a kindergarten with planetary embryos, excitedly interchangeable, disturbed the other orbits of the other and even collided until only the well -defined and stable orbital configurations we know today,” said Franco.
Franco and its co-researchers turned to simulations for smoothed particle hydrodynamics (SPH) to test the idea. This widespread method simulates the behavior of gases, liquids and solids while they are on the move. SPH simulations are particularly useful in the context of collisions such as those between planets.
“Through detailed simulations in smoothed particle hydrodynamics, we found that it is possible to reproduce both the overall mass of Mercury and the unusual ratio of metal to silics with high precision. The model rate of the model was less than 5%,” said Franco. It is an unusual ratio of metal to silicate refers to the fact that the core is metallic while the coat and the crust are silicate.
These screenshots from the simulations show how the impact event happened. “The proto-mercise (0.13 m⊕) is represented by a pink coat and a turquoise core. The goal is shown by a red coat and a yellow core,” the authors explain. The speed of action is relatively low and the impact angle is 32.5 degrees. (b) and (c) show the effects and the material that is blown away. (d) shows the mercury candidate with 0.056 earth masses, very close to the measured 0.055 earth masses. Photo credits: Franco et al. 2025. Natastr
“We assumed that Merkur would initially have a similar composition as the other terrestrial planets. The collision would have removed up to 60% of its original coat, which would explain its increased metallicity,” explains Franco.
But when mercury is the result of a mass strip collision, what happened to the material blown out in space? The modeling of the effects between objects of different sizes means that mercury has re -accreted most of the lost mass. In this case, mercury would not have the structure it does now.
“In these scenarios, the material demolished during the collision is reinstalled by the planet itself. If this were the case, mercury would not have its current disproportion between the core and coat. In the model we propose, we will, depending on the initial conditions, part of the material crack.
https://www.youtube.com/watch?v=VR8LZ9RPD40
At the beginning of the solar system, the conditions would have prevented the mass from being resolved again.
“The scenario proposed in this work takes place during the initial tens of millions of planetary formation if several mechanisms could prevent an essential reakretion of rubble,” the authors write. There would have been numerous planets and planet embryos that could have scattered the gravity of the debris.
Another option is that his neighbor Venus became a bit more massive due to the effects.
“If the effects occurred in nearby orbits, there is a possibility in the fact that this material was recorded by another planet in education, possibly Venus.
The expansion of this understanding requires a geochemical examination not only mercury, but also from meteorites and possibly also a sample made of mercury itself. There are concepts for a mercury sample return mission, but they are limited to the conceptual status. In the mid -2000s, the ESA studied a solar sail idea for a rehearsal withdrawal in mercury, but it was more of a thought experiment than a suggestion. Nevertheless, the solar sail idea will not disappear.
https://www.youtube.com/watch?v=f1X4IWBXG-0
The Mission Esa/Jaxa Bepicolombo will reach Mercury in 2026 and has a few complementary orbiter that carry out a comprehensive examination of the planet. Together they wear more than 20 science instruments. It measures the solid and liquid cores from Mercury and determines their sizes. The magnetic and gravity fields of the planet will also map. The results may not confirm this new effects, but more detailed data will undoubtedly advance the scientific understanding of the mercury.
“Mercury remains the least researched planet in our system. But that changes. There is a new generation of research and missions, and many interesting things will still come,” said Franco.
Comments are closed.