Mars is a planet of limited size, but for scientists who study the birth the Solar System, is too small.
"This is an outstanding problem in the formation of terrestrial planets ", said Dr. David Minton from the Southwest Research Institute. " Anyone doing simulations on the formation of terrestrial planets, he will always be that Mars is 5-10 times larger than the reality. "
Minton and his colleague Dr. Hal Levison have created new simulations to solve the mystery of its small size, including the effect of what is known as " migration of planetesimals " and small objects called Minton " Marstinis ", which could radically change our minds and the recent bombings in the late period of the formation of the Solar System.
Planetary scientists agree that the terrestrial planets would have formed very rapidly within the first 5-10 million years of the Solar System and Earth's moon would have made an impact between a Mars-sized object (called Theia) with the proto-Earth in the same period. Then
heavy bombing would take place with the formation of a large number of impact craters on the moon within a span of just 70 million years on Earth and, by deduction, Mercury, Venus and Mars.
Most theories on the formation planet can not explain this intense period of bombardment so late in the history of the Solar System.
Levison and his team, proposed in 2005 the famous "Nice model" , where the bombing was a late consequence of the rapid migration of the giant planets that destabilized a disc composed of numerous small "planetesimals". This caused a sudden and massive movement of asteroids and comets toward the inner solar system.
But, according to the model, the planetesimals would probably also caused the migration of planets.
The planets were formed from a giant disk composed of gas, dust, dirt, rocks and ice that surrounded the Sun debris coalesced to form larger objects and simulations show that the planet has built larger smaller items by dispersing other items with different angular momentum.
The perturbations of small rocky or icy objects that surrounded a larger object could have caused the displacement of diverting it from its orbit. According to Minton
fact: "Every time they met the planetesimals larger object, they actually caused a little push in the opposite position of the object larger" .
Minton Levison and have applied the same natural migration for the formation of terrestrial planets.
"In the case of Mars, we must imagine these planetary embryos located in the zone of influence of the Earth and Venus" , said Minton. "Then we would have a growing embryo that becomes the size of Mars and begin to migrate because of the shift imposed by other planetesimals. So as they move across the disk, has moved away from the area of \u200b\u200bdense material."
So, the growth of Mars stopped at the current volume, because the migration took him away from the area full of useful material for its further growth. According to Minton, their simulation explains very well because of its small size.
"We have made numerous calculations and the migration must have been rather rapid" said, "and Mars can be migrated before reaching larger.
A similar scenario, with Mars expelled to the edge of the disk material at 1.5 AU, where it is now, has enabled the Earth and Venus to reach its current size. The migration of Mars might have caused the collection of planetesimals in gravitational resonance.
"The reason for this is not obvious," said Minton but "the same thing could have occurred in the outer Solar System that is what has given the present orbit Pluto. We believe that Pluto was actually taken in a 3:2 resonance with Neptune when it migrated to its current position. "
The plutinos are other objects in the Kuiper Belt near Pluto, and being in resonance, spin around the Sun three times for every 2 times of Neptune. There are also two Tinos, which are trapped in a 1:2 resonance with Neptune, which are located towards the outer edge of the Kuiper belt.
The new simulations show that these resonance lines almost always act as a snow plow, and when Neptune migrated outwards picked up with him all these small icy bodies including Pluto and plutinos.
This phenomenon could also have happened with Mars and migrate through the disc while it may have picked up small objects with them.
"I decided to call these objects Marstinis, referring to plutinos" Minton said with a smile. But the interesting thing is that Marstinis of a 3:2 resonance with Mars is actually a very unstable area.
"There was actually a resonance with Saturn, during the latter stages of the bombing, because before then, was in a different position." So it was only after the planets giganti sono migrati alla loro posizione attuale che questa posizione risonanza รจ diventato instabile. Quindi pensiamo che questi Marstinis sarebbero stati stabili e in quel periodo di transizione tra la fine della formazione dei pianeti e i pesanti bombardamenti, tutto ad un tratto questa regione divenne instabile quando i pianeti si spostarono dalle precedenti posizioni a quelle attuali".
Sopra una rappresentazione artistica del "Late Heavy Bombardment", quella devastante pioggia di asteroidi che ridusse la Luna ad un cimitero di crateri e che probabilmente contribui a portare l'acqua sulla Terra tramite gli impatti cometari.
Potrebbero i Marstinis essere i responsabili del "Late Heavy Bombardment"?
"Questi Marstinis furono spinti dalle regioni di formazione planetaria verso la fascia degli asteroidi e poi ad un tratto i pianeti migrati e l'intera regione divennero instabili e molti finirono nel Sistema Solare interno finendo per colpire la Luna". Abbiamo ragione di pensare che gli oggetti che hanno colpito la Luna durante il Late Heavy Bombardment erano una specie di asteroidi ma non esattamente come quelli che vediamo ora" , ha detto Minton. "Dunque, ci sono alcuni argomenti che potrebbero essere approfonditi con una analisi chimica degli impatti lunari, per stabilire se si trattava di asteroidi o comete".Questi interrogativi could be solved by going back to the moon and there is almost no other better place where you can go. The lunar surface is indeed one of the best places to understand the history of the Solar System. "
Minton has presented its findings at the Lunar and Planetary Science Conference in the month of March 2011.
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