The finding, if correct, would offer evidence for planetary migration in the early solar system, particularly in support of an idea called the Nice Model, with Saturn, Uranus and Neptune all moving outward, and Jupiter inward slightly, over a few hundred million years. This would have perturbed organic-laden asteroids leftover from the formation of the planets, sending them pinging around the solar system.
“It’s an exciting discovery with implications for the origins of life,” Dr. Öberg said.
Most of these leftover objects in the present day are known as trans-Neptunian objects and orbit in the Kuiper belt beyond Neptune. Many are red in color, like Arrokoth, the rock that NASA’s New Horizons mission got a close-up of in 2019. 203 Pompeja and 269 Justitia both appear to match them.
“People have been talking about some fraction of asteroids coming from the Kuiper belt for quite a while now,” said Josh Emery, a planetary scientist from Northern Arizona University who was not involved in the paper. He said the research “definitely takes a step” toward finding evidence to support that hypothesis.
Not everyone is convinced just yet. Dr. Levison, who was also not involved in the paper, says objects should become less red as they approach the sun. Even captured asteroids in Jupiter’s orbit known as Trojans, thought to possibly be trans-Neptunian objects, aren’t this red. “It seems to be inconsistent with our models,” said Dr. Levison, who is the head of NASA’s Lucy mission, which is scheduled to launch in October to study Jupiter’s Trojans.
Dr. Marsset agrees that it’s not clear why they would be so red, but it is possibly related to how long it took them to become implanted into the asteroid belt. Some Trojans may also be as red, but haven’t been found yet.
To truly confirm the origin of 203 Pompeja and 269 Justitia, a spacecraft would likely need to visit them. Such a mission could potentially offer a glimpse at the outer solar system, but without spending a decade or more to fly there.
“You could flyby one of these strange asteroids, and a more typical asteroid for comparison,” Dr. Emery said. “That would be a really compelling spacecraft mission.”