The latest image of Ultima Thule released by the New Horizons team at the John Hopkins University Applied Physics Laboratory reveals a relatively smooth surface to the snowman-shaped Kuiper Belt object (KBO), giving scientists new clues about conditions in the Kuiper Belt itself.
New Horizons’ Latest Image Reveals New Information—and Mysteries
The latest images of Ultima Thule, formally known as 2014 MU69, reveals new data, and new mysteries, about the most distant object ever visited by a man-made probe.
The image, taken about 4,200 miles from Ultima Thule and about 7 minutes before New Horizons’ closest approach, reveals a relatively smooth surface for the two lobes that make up the object as well as different colored regions that give scientists new clues about the composition of the KBO and how it was formed.
"This new image is starting to reveal differences in the geologic character of the two lobes of Ultima Thule, and is presenting us with new mysteries as well," according to Alan Stern of Boulder, Colorado’s Southwest Research Institute, where he serves as the Principal Investigator. "Over the next month, there will be better color and better resolution images that we hope will help unravel the many mysteries of Ultima Thule."
Relative Smoothness Reveals a Quieter Kuiper Belt
“The thing is just not covered in craters,” says Kelsi Singer, a planetary scientist at the Southwest Research Institute.
Singer and others have theorized that the proto-planets that formed the planets of the solar system billions of years ago formed very fast relative to their age. When New Horizons flew past Pluto in 2015, the largest object in the Kuiper Belt turned out to be much smoother than expected.
In the case of Pluto, this could be a result of geological forces on its surface, such as the movement of glaciers, that erased evidence of such craters; but its moon, Charon, was also surprisingly smooth.
Charon isn’t large enough to be geologically active, so there should be evidence of impact craters on its surface if the Kuiper Belt were an active shooting gallery of asteroids and large KBOs smacking into each other.
The lack of impact craters on Charon, and now on Ultima Thule, suggests that Singer is correct that the proto-planets of the early solar system formed quickly from the nebulous gases and materials of the nascent solar system, absorbing most of the material present and leaving relatively little behind.
Further Data to Come
It may be premature to say definitively one way or the other, says Alessandro Morbidelli, a planetary scientist at the Côte d’Azur Observatory in Nice, France.
Pointing to the resolution of the newest image, which is about 440 feet per pixel, impact craters might not show up clearly enough to identify. The higher resolution images that New Horizons took on its closest approach have yet to be transmitted, which Morbidelli says will be the “ultimate test.”
New Horizons, now approximately 4.13 billion miles from Earth and traveling more than 31,500 miles an hour, will continue to transmit data from its January 1st, 2019 fly-by of Ultima Thule for a while.
It’s expected to transmit the last bit of data from its memory in September 2020, which takes a little more than 6 hours to reach us here on Earth.