Saturn-like rings around the Sun stopped our planet becoming ‘super-Earth’, new study suggests

Super-Earths are massive rocky planets seen around at least 30 per cent of sun-like stars in the galaxy

Adam Smith
Wednesday 12 January 2022 16:58
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The Sun had rings of dust and gas similar to Saturn that may have played a vital role in the formation of the Earth, a new study suggests.

“In the solar system, something happened to prevent the Earth from growing to become a much larger type of terrestrial planet called a super-Earth ,” Rice University astrophysicist André Izidoro, said.

Super-Earths are massive rocky planets seen around at least 30 per cent of Sun-like stars in the galaxy.

Using a supercomputer to simulate the formation of the solar system, the model produced rings around the Sun like those seen around young stars.

The model assumes that three bands of high pressure arose within the young Sun’s disk of gas and dust – dubbed “pressure bumps” – that have also been observed in ringed stellar disks around distant stars.

“If super-Earths are super-common, why don’t we have one in the solar system?” Izidoro said. “We propose that pressure bumps produced disconnected reservoirs of disk material in the inner and outer solar system and regulated how much material was available to grow planets in the inner solar system.”

Scientists have thought for decades that gas and dust in disks gradually became less dense, but computer simulations told a different story – that planets are unlikely to form in smooth-disk scenarios.

“In a smooth disk, all solid particles — dust grains or boulders — should be drawn inward very quickly and lost in the star,” said astronomer and study co-author Andrea Isella , an associate professor of physics and astronomy at Rice. “One needs something to stop them in order to give them time to grow into planets.”

When particles move faster than the gas around them, they “feel a headwind and drift very quickly toward the star,” Izidoro said.

The study’s model assumed pressure bumps formed in the early solar system at three places.

“It’s just a function of distance from the star, because temperature is going up as you get closer to the star,” said geochemist and study co-author Rajdeep Dasgupta , the Maurice Ewing Professor of Earth Systems Science at Rice. “The point where the temperature is high enough for ice to be vaporized, for example, is a sublimation line we call the snow line .”

At the silicate line, the basic ingredient of sand and glass, silicon dioxide, became vapor. This produced the Sun’s nearest ring, where Mercury, Venus, Earth and Mars would later form.

The middle ring appeared at the snow line, and the farthest ring at the carbon monoxide line.

Izidoro said the delayed appearance of the sun’s middle ring in some simulations led to the formation of super-Earths, which points to the importance of pressure-bump timing.

“By the time the pressure bump formed in those cases, a lot of mass had already invaded the inner system and was available to make super-Earths,” he said. “So the time when this middle pressure bump formed might be a key aspect of the solar system.”

The study was published online in Nature Astronomy,

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