NASA's far-flung New Horizons spacecraft has revealed for the first time a clear picture of Ultima Thule, the icy object it flew by shortly after midnight on New Year's Day.
The city-size object is made up of a pair of roughly spherical lobes, mission scientists said at a press conference Wednesday at the Johns Hopkins Applied Physics Lab in Laurel, Maryland, to discuss the new findings.
The scientists dubbed the larger lobe "Ultima," the smaller one "Thule."
"The bowling pin is gone," Alan Stern, a scientist at the Southwest Research Institute in Boulder, Colorado, and the mission's principal investigator, said, referring to the shape scientists had preliminarily ascribed to the object. "It’s a snowman if it’s anything at all."
The images were obtained by cameras aboard the spacecraft as it sped by the "bi-lobed" object, which orbits the sun about 1 billion miles beyond the orbit of Pluto. At that distance, it takes radio signals more than six hours to travel back to Earth.
Stern said only about 1 percent of the data collected by the spacecraft had been beamed back to Earth. In coming days, the scientists will be getting images with greater detail.
The best image revealed Wednesday has a resolution of about 130 yards per pixel, for a total of 2,800 pixels in the image. In the next few days, we'll see images with resolutions four times finer with a full megapixel of data in the image.
The new images show that Ultima and Thule isn't a bowling pin- or peanut-shaped object, as scientists had previously thought. They also show that the surfaces of the lobes are as dark as soil, with some regions reflecting as much as 13 percent of sunlight and others as little as 6 percent.
The sunlight falling on the object is about 2,000 times dimmer than it is on Earth.
There are hints of hills but no craters on Ultima and Thule, though the scientists said we’ll know more about that on Thursday, when stereo imaging becomes available.
The object is reddish in color, perhaps because it's made up of methane ice or nitrogen ice that has been reddened by chemical reactions. We should find out on Thursday the surface composition of the object, pending a review of data already beamed back from a spectrometer aboard the spacecraft.
It will take a total of 20 months for all the data to reach the scientists on Earth, in part because New Horizons is just one of the many spacecraft being monitored by the giant antennas that make up NASA’s Deep Space Network.