New Horizons’ LORRI captures details on Ultima Thule’s surface
A risky maneuver by the New Horizons team aimed at obtaining closeup, very high resolution images of Ultima Thule’s surface just before the spacecraft’s closest approach has succeeded, revealing that surface in unprecedented detail.
The photos, captured by the Long Range Reconnaissance Imager’s (LORRI) telephoto lens just six-and-a-half minutes before closest approach, from a distance of just 2,200 miles (3,500 kilometers), have a resolution of approximately 110 feet (33 meters) per pixel. They are the latest to be returned by the spacecraft.
Taken as New Horizons was speeding toward Ultima Thule at 32,000 mph (51,000 kph), the images show significantly more surface detail than those previously returned by the spacecraft, including bright circular regions and small dark pits near the terminator that divides the KBO’s day and night sides.
Knowing the challenges of obtaining such sharp images as the probe sped by, mission scientists described their plans to obtain them as a “stretch goal,” something desirable but risky, with questionable chances of success. The effort did benefit from the spacecraft having been in a favorable viewing angle and LORRI’s high spatial resolution.
“Getting these images required us to know precisely where both tiny Ultima and New Horizons were—moment by moment—as they passed one another at over 32,000 miles per hour in the dim light of the Kuiper Belt, a billion miles beyond Pluto. This was a much tougher observation than anything we had attempted in our 2015 Pluto flyby,” New Horizons Principal Investigator Alan Stern of the Southwest Research Institute (SwRI) in Boulder, Colorado, said in a press release.
New Horizons had to fly three times closer to Ultima Thule than it did to Pluto to obtain these images. The entire encounter was more challenging than the Pluto flyby because Ultima Thule is much smaller than Pluto and is a billion miles further from the Sun. Additionally, the spacecraft is three years older than it was at Pluto and contains less fuel than it did three years ago.
Several successful ground-based observations of Ultima Thule occulting individual stars in 2017 and 2018, seen from Argentina, Senegal, South Africa, and Colombia and assisted by the European Space Agency’s (ESA) Gaia observatory, which provided data on the locations of stars used to observe the occultations, made the extremely precise navigation needed to obtain these latest images possible.
“These ‘stretch goal’ observations were risky because there was a real chance we’d only get part or even none of Ultima in the camera’s narrow filed of view,” Stern said. “But the science, operations, and navigation teams nailed it, and the result is a field day for our science team. Some of the details we now see on Ultima Thule’s surface are unlike any object ever explored before.”
Science team members are studying these latest images in an attempt to discern what caused the craters and pits on the most distant and primitive solar system object ever explored by a spacecraft.
“Whether these features are craters produced by impactors, sublimation pits, collapse pits, or something entirely different, is being debated in our science team,” said deputy project scientist John Spencer, also of SwRI.
Using nine individual high-resolution images, mission scientists created a composite image in which Ultima Thule’s various surface colors and textures are clearly visible. They also put together a very brief movie by combining 14 separate images, depicting the KBO passing by as seen from New Horizons.
All raw images returned by LORRI, including the ones used to create the composite, are posted to the instrument’s website every Friday for public viewing.
Video courtesy of NASA
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.