A New Horizons study shows that small objects in the Kuiper belt are surprisingly rare

Using New Horizons data from the Pluto-Charon flyby in 2015, a team of scientists led by the Southwest Research Institute indirectly discovered a distinct and surprising lack of very small objects in the Kuiper Belt. Evidence of the rarity of small Kuiper Belt (KBO) objects comes from New Horizons imagery which revealed a shortage of small craters on Pluto's largest satellite, Charon, indicating that the impactors had a diameter of 91 to 1.6 km. must also be rare.

The Kuiper Belt is a region of donut-shaped frozen bodies located beyond the orbit of Neptune. Because the small objects of the Kuiper Belt were part of the "raw materials" from which the planets were formed, this research provides new information about the origin of the solar system. This research was published in the March 1 issue of the prestigious journal Science.

"These smaller objects in the Kuiper belt are far too small to be seen with such remote telescopes," said Dr. Kelsi Singer of SwRI, lead author of the journal and co-investigator of NASA's New Horizons mission. . "New Horizons flying directly over the Kuiper belt and collecting data was essential to learn more about the small and large bodies of the belt."

"This landmark discovery by New Horizons has profound implications," said lead researcher Dr. Alan Stern, also of SwRI. "Just as New Horizons revealed Pluto, its moons, and more recently, the KBO dubbed Ultima Thule in exquisite detail, Dr. Singer's team has revealed key details about the KBO population at scales that we do not can not see directly from the Earth. "

Craters on solar system objects record smaller body impacts, providing insights into the history of the object and its place in the solar system. Because Pluto is so far from the Earth, little was known about the surface of the dwarf planet before the epic flyby of 2015. Observations of the Pluto and Charon surfaces revealed various features, including mountains up to 4 km ( 13,000 feet) and vast glaciers of ice with nitrogen. The geological processes on Pluto have erased or altered some of the evidence of the history of its impacts, but the relative geological stasis of Charon has provided a more stable record of impacts.

"An important part of New Horizons' mission is to better understand the Kuiper Belt," said Singer, whose research on the geology of the frozen moons of Saturn and Jupiter positions it to understand the observed surface processes on KBO. "With the successful flythrough of Ultima Thule earlier this year, we now need to study three distinct planetary surfaces.This article uses the Pluto-Charon flyover data, which indicates fewer small craters of impact than expected and the preliminary results of Ultima Thule's support this find. "

Typical planetary models show that 4.6 billion years ago, the solar system formed from the gravitational collapse of a giant molecular cloud. The Sun, planets and other objects formed as materials in the collapsing cloud aggregate into a process called accretion. Different models result in different populations and locations of objects in the solar system.

"This surprising lack of small KBOs changes our view of the Kuiper Belt and shows that its formation or evolution, or both, were somewhat different from those of the asteroid belt between Mars and Jupiter," he said. Singer. "Maybe the asteroid belt has more small bodies than the Kuiper belt because its population is experiencing more collisions that break down larger objects into smaller objects."

The article published in Science is titled "The craters of impact on Pluto and Charon indicate a deficit of small objects of the Kuiper belt."

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More information:
K.N. Singer el al., "Craters of impact on Pluto and Charon indicate a deficit of small objects of the Kuiper belt" Science (2019). science.sciencemag.org/cgi/doi… 1126 / science.aap8628