From the origin of the oversized nucleus of mercury to the strange volcanism of Venus, the diversity of the telluric planets of the solar system could be explained by the collisions which occurred at the very end of their formation. A study published in Nature Highlights this phase long neglected.
Mercure, VenusVenusEarth and Mars: these four planets are said to be telluric, that is to say that they consist mainly of rocks and metalsmetalsunlike gaseous planets which mainly contain volatile elements. The telluric planets are observed in the internal area of ​​the solar system due to the heterogeneous initial distribution of physical elements and parameters in the protoplanetary disc. The very high temperature in the internal zone means that only certain materials (including the ferfer and silicatessilicates) can be condensed from gazgaz disc. Due to ventsvents Stellar, this region is as rich in gas than the external area. This explains why the planets being formed as close as possible to SoleilSoleil are mainly composed of rocks.
Planetary accretion: the very last phase could have played a major role in the characterization of telluric planets
However, none of these four telluric planets are alike. However, they were all formed by the same process ofaccretionaccretion small rocky bodies. If the respective position of Mercury, Venus, the Earth and Mars compared to the sun at the time of accretion makes it possible to explain a good part of these differences, it is however not the only parameter to have played a role in the shaping of these planets.
A new study thus reveals the importance of the latest phase of accretion. Although they have accumulated about 99 % of their massemasse in 60 to 100 million years, the telluric planets of our Solar systemSolar system Then continued to grow very slightly thanks to much smaller impacts of bodies. This phase, which is called late accretion, would have participated only in 1 % in the constructionconstruction Planets, but its role in the final shaping is far from anecdotal. These late collisions, although rare, would have exerted a strong influence on the internal, crustal and atmospheric evolution of the four planets.
Various late collision schemes for different results
Of the digital simulationsdigital simulations thus allowed a team of researchers to observe what were the distinct consequences of this late accretion for each case. The results show that it would be possible that Mercury inherited its large iron nucleus after a major impact. The interior of Venus would have been permanently heated by a series of significant impacts, fueling a volcanismvolcanism Very active which is still relevant. March dichotomy could also be linked to a late massive impact. While for the earth, it is suggested that more moderate impacts could have started a Plates tectonicsPlates tectonics transitional, thus promoting the start of a large geological cycle that allowed theemergenceemergence and the development of life.
Habitability of the planets: the importance of late accretion
The importance of this late accretion could also have played a very important role in the quality of theatmosphereatmosphere of these different planets. Depending on the chronology of events, these impacts could have either sprayed an emerging atmosphere, or on the contrary enrich it in volatile materials. The habitability of a planet could therefore be played mainly in this final accretion phase.
These results, published in the journal Nature, brings a new reading grid that guides research both in our solar system and to the distant exoplanetsexoplanets.
