Mercury was photographed by NASA’s Messenger spacecraft in 2008. NASA/JPL/JHUAPL/Carnegie Institution of Washington by The New York Times.
Mercury is useless.
It is a strange lump of rock with a composition unique to its neighboring rocky planets.
“That’s too much densesays David Rothery, a planetary scientist at the Open University of England.
Most of the planet, the closest to the sun, is occupied by its core.
It doesn’t have a thick mantle like Earth has, and no one is sure why.
One possibility is that the planet is larger, perhaps twice its current volume or more.
Billions of years ago, the new proto-Mercury, or super-Mercury, may have been hit by a large object, tearing its outer layers and leaving the rest we see.
Although this is a good idea, there is no direct evidence of it yet.
But some researchers think they have found something.
In a paper presented at the Lunar and Planetary Science Conference in Houston in March, Camille Cartier, a planetary scientist at the University of Lorraine in France, and her colleagues spoke of its components. proto-Mercury they can be hidden in museums and other meteorite collections. Studying them can unlock the mysteries of the planet.
“We don’t have any Mercury samples” at this time, Cartier said.
Obtaining such specimens would “be a small revolution” in understanding the natural history of the smallest planet in the solar system.
According to the Meteoritical Society, nearly 70,000 meteorites have gathered around the world from areas as remote as the Sahara and Antarctica, and have found their way into museums and other collections.
Most came from asteroids released from the belt between Mars and Jupiter, while more than 500 came from the Moon.
More than 300 are from Mars.
Notably none of the documented rocks in the galaxy are confirmed meteorites from the innermost planets of our solar system, Venus and Mercury.
It is generally hypothesized that it is difficult, though not impossible, for lips closer to the sun and its gravity goes to the solar system.
Among the small number of meteorite collections is a rare type of space rock called aubrite.
Named for the town of Aubres in France, where the first meteorite was found in 1836, the aubrites are pale in color and contain small amounts of metal.
They are low in oxygen and appear to have formed in an ocean of magma.
About 80 aubrite meteorites have been found on Earth.
For these reasons, they appear to correspond to scientific models of conditions on the planet Mercury in the early days of the solar system.
“We’ve often said that aubrites are very good analogues of Mercury,” Cartier said.
But scientists have stopped saying they are actually pieces of Mercury.
Klaus Keil, a scientist at the University of Hawai’i at Manoa who died in February, argued in 2010 that aubrites were more likely to come from other types of asteroids than something released from Mercury, with some scientists favoring a group of asteroids. in the belt called E-type asteroids.
Among their evidence were signs that the aubrites were attacked by sun Wind, something that must be protected by Mercury’s magnetic field.
Cartier, however, has another idea.
What if the aubrites came from Mercury?
Following the hypothesis that a large object collided with a younger Mercury, Cartier said that a large amount of material would be thrown into space, nearly a third of the mass of the planet.
A small amount of that debris would have been blown away by the solar wind so far is the asteroid belt, which forms E-type asteroids.
There, asteroids have remained for billions of years, occasionally colliding and constantly being struck by the solar wind, explaining the solar wind imprint seen on the aubrite.
But eventually, he suggested, some pieces were pushed towards Earth and fell on our planet as aubrite meteorites.
The low level of nickel and cobalt found in aubrites match what we expect from proto-Mercury, Cartier says, while data from NASA’s Messenger spacecraft that orbited Mercury between 2011 and 2015 supports similarities between of the composition of Mercury and aubrites.
“I think aubrites are the highest part of the mantle of a large protomercury,” Cartier said.
“It could solve the origin of Mercury.”
If true, it means we have pieces of Mercury, even an older version of the planet, hidden in drawers and display cases for more than 150 years.
“It’s going to be incredible,” said Sara Russell, a meteorite expert at the Natural History Museum in London, who was not involved in Cartier’s work.
The museum has 10 aubritas in its collection.
Other experts have reservations about the hypothesis.
Jean-Alix Barrat, a geochemist at the University of Western Brittany in France and one of the few aubrite experts in the world, does not think there is enough aubrite material in meteorite collections to determine if its content matches in super Mercury models. .
“The authors are pretty optimistic,” he said.
“The data they use is not enough to substantiate their conclusions.
In response, Cartier said he removed potential contaminant rocks from his aubrite samples to obtain representative nickel and cobalt levels, which he was “confident” were correct.
Jonti Horner, an expert in asteroid dynamics at the University of Southern Queensland in Australia, isn’t sure if material from Mercury could have entered a stable orbit in the asteroid belt and hit Earth billions of years ago.
“It doesn’t make sense to me from a dynamics perspective,” he said.
Christopher Spalding, a planet formation expert at Princeton University and a co-author of the Cartier study, said his model shows that the solar wind can blow material from Mercury enough to link it in E-type asteroids.
“The young sun is very magnetic and rotates fast,” he says, making it a “solar wind.”rotation”Which could send pieces of Mercury into the asteroid belt.
Another possibility, which has not yet been modeled, is that the gravitational weights of Venus and Earth scattered the material farther before some returned to our planet.
Cartier’s proposal could be reviewed soon. A joint European-Japanese space mission called BepiColombo is on track to orbit Mercury in December 2025. Cartier presented his idea to a group of BepiColombo scientists in early May.
“I was amazed,” said Rothery, a member of the BepiColombo science team.
He said his mission could find evidence of nickel on the surface of Mercury that would link the planet more precisely to the collected aubrites.
It won’t be “simple,” he says, because Mercury’s surface today will be just like the rest of proto-Mercury.
But he said the results would “help feed the model.”
Willy Benz, an astrophysicist at the University of Bern in Switzerland who first proposed the idea of a proto-Mercury, said that if aubrites derived from Mercury, they would add to the evidence for an active and violent early solar system. .
“This will show that giant effects are fairly common,” he said, and that they “play an important role in shaping the architectures of planetary systems.”
Cartier further analyzed his ideas by melting a few samples of aubrite under high pressure.
If these experiments and BepiColombo data support their hypothesis, aubrites could be rare in our meteorite collections to become some of the most amazing meteorites collected: pieces of the inner world of the solar system .
c.2022 The New York Times Company
Source: Clarin
