We鈥檝e just gotten our first good look at a tiny, distant world called 2014 MU69. The small space rock, nicknamed Ultima Thule or simply MU69, is 6.6 billion kilometres away, making it the most distant object we鈥檝e ever explored.
Early on New Year鈥檚 Day, NASA鈥檚 New Horizons spacecraft hurtled past MU69,聽passing within 3500 kilometres of the small rock鈥檚 surface at a speed of 14 kilometres per second, taking a flurry of pictures and science data as it passed.
The first pictures, taken shortly before the flyby, revealed that MU69 has two elongated lobes, like a bowling pin or a peanut shell. The image resolution was not high enough to tell whether the two lobes were separate objects or attached to one another.
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Now, new images taken about 30 minutes before the spacecraft鈥檚 closest approach have shown that it looks more like a snowman 鈥� the two lobes appear to be a pair of spheres that are just touching in what鈥檚 called a contact binary. In a 2 January press conference, mission leader Alan Stern announced that the larger lobe would be called Ultima and the lesser Thule.
New Horizons co-investigator Jeff Moore said that because the two lobes聽show no obvious signs of damage from a collision, they probably hit one another slowly, at about a walking pace. 鈥淚f you had a collision with another car at those speeds, you might not even bother to fill out the insurance forms,鈥� he said.
The first colour images also confirm that MU69 is red, perhaps because of methane or nitrogen ices on its surface, said co-investigator Carly Howett. More data on the surface composition and topography, along with better images, will continue to stream down over most of the next two years.
MU69 appears to be a pristine planetary building block, or planetesimal, left over from the early solar system, so researchers hope that it will tell us about the formation of the planets. 鈥淲hat we鈥檙e looking at is essentially one of the first planetesimals,鈥� said Moore, 鈥淭hese are the only remaining basic building blocks in the backyard of the solar system.鈥�
