Scientists led by Sunao Hasegawa of JAXA, the Japanese space agency, reported Monday in The Astrophysical Journal Letters that two objects spotted in the asteroid belt between Mars and Jupiter appear to have come from beyond Neptune. The discoveries may one day provide direct evidence of the chaos that existed at the start of the solar system.
“If that were true, that would be a huge deal,” says Hal Levison, a planetary scientist at the Southwest Research Institute in Colorado, who was not involved in the research. Earth’s stellar neighborhood is fairly stable today. But 4 billion years ago, chaos reigned as the orbits of Jupiter and other giant planets beyond may have changed. The gravitational havoc caused by this planetary dance likely threw chunks of rock and ice all over the place.
“It was very dynamic,” said Karin Öberg, a solar system evolution expert at Harvard University who was not involved in the new study. Some of these rocks settled in the space between Mars and Jupiter and became the asteroid belt. Most of the material is believed to be fairly similar pieces of inactive rock that failed to form planets.
But then there are two objects called 203 Pompeja and 269 Justitia.
They orbit about 2.7 and 2.6 times the Earth-Sun distance, well inside the asteroid belt. 203 Pompeja, about 70 miles in diameter, appears to be structurally intact, while 269 Justitia, only about 35 miles away, is likely a fragment from a previous collision. Both have stable circular orbits, which means they must have settled in this space a long time ago.
Both also have an unusual color. Objects in the inner solar system tend to reflect more blue light because they are devoid of organic matter – things like carbon and methane – while objects in the outer solar system are redder because they contain a lot. organic matter, perhaps the building blocks of life. Earth.
“To have this organic material, you first have to have a lot of ice on the surface,” said Michaël Marsset of the Massachusetts Institute of Technology, co-author of the article. “So they had to train in a very cold environment. Then the solar irradiation of the ice creates these complex organic compounds.
It turns out that these two rocks are extremely red – redder than anything seen in the asteroid belt. Although provisional clues of other red asteroids have been found, these two appear to be special.
The discovery, if correct, would offer evidence of planetary migration at the start of the solar system, particularly in support of an idea called the Nice model, with Saturn, Uranus, and Neptune all moving outward. , and Jupiter slightly inward, over a few hundred million years. . This would have disrupted the organic matter-laden asteroids remaining from the formation of the planets, sending them spinning around the solar system.
“This is an exciting discovery with implications for the origins of life,” said Dr Öberg. Most of these objects remaining today are known as Transneptunian objects and orbit the Kuiper Belt beyond Neptune. Many are red in color, like Arrokoth, the rock that NASA’s New Horizons mission snapped up in 2019. 203 Pompeja and 269 Justitia both seem to match them.
The writer is a reporter for the NYT
The New York Times