Now well clear of the sun on the far side of the solar system,is downlinking recorded data from its a billion miles past Pluto, including the sharpest view yet of the twin-lobe body.
In a brief release from the Johns Hopkins University Applied Physics Laboratory, researchers said the latest high-resolution image "is the clearest view yet of this remarkable, ancient object in the far reaches of the solar system."
The image was captured by the wide-angle Multi-color Visible Imaging Camera, or MVIC, taken at a distance of 4,200 miles from Ultima Thule just seven minutes before New Horizons made its closest approach. The image was stored aboard the spacecraft and transmitted back to Earth on Jan. 18-19.
"The oblique lighting of this image reveals new topographic details along the day/night boundary, or terminator, near the top," according to the APL release. "These details include numerous small pits up to about 0.4 miles in diameter. The large circular feature, about 4 miles across, on the smaller of the two lobes, also appears to be a deep depression.
"Not clear is whether these pits are impact craters or features resulting from other processes, such as 'collapse pits' or the ancient venting of volatile materials."
The two lobes show "intriguing light and dark patterns of unknown origin, which may reveal clues about how this body was assembled during the formation of the solar system 4.5 billion years ago. One of the most striking of these is the bright 'collar' separating the two lobes."
Launched 13 years ago,in July 2015, racing by at a distance of 7,800 miles to collect the first close-up pictures and a wealth of data about the solar system's most famous dwarf planet.
Looking for another target beyond Pluto, the Hubble Space Telescope spotted a small body catalogued as 2014 MU69 that later was named Ultima Thule in a NASA naming contest. After the Pluto flyby was complete, New Horizons was ordered to change course, setting up the Jan. 1 Ultima Thule flyby.
The strange-looking body is one of the countless chunks of debris in the Kuiper Belt beyond Pluto thought to be left over from the original cloud of gas and dust that coalesced to form the solar system. It appears to be made up of two bodies that gently collided and stuck together in the distant past.
"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," Alan Stern, the New Horizons principal investigator, said in a statement.
"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."