s of MU69 are not perfect ellipsoids, according to Jeff Moore, the mission’s lead investigator for geology and geophysics at NASA Ames Research Center in Moffett Field Calif. Compared to a smooth ellipse, there are elevation changes greater than 1 kilometer on the larger lobe. There are also noticeable divots that flatten out portions of the rim of the smaller lobe.
4. No Moons Yet
“We’ve seen bodies one and two, so the question now is, What about bodies three, four, five, and so on?” asked Mark Showalter, New Horizons coinvestigator from the SETI Institute in Mountain View, Calif. The object’s likely formation scenario suggests that there may be smaller objects in orbit around MU69. Finding satellites would also help reveal the body’s total mass and average density, which are key for pinpointing its interior structure and composition, Moore said. “We have not found any other bodies in the system,” he said, “but we’re still looking.”
5. Slowly Rotating
The object “rotates with a period of about 15 hours,” said mission coinvestigator Cathy Olkin from SwRI. What’s more, MU69 rotates in such a way that it keeps roughly the same surface area facing Earth at all times, she said, similar to an airplane propeller. An impact with a smaller object may have slowed down MU69’s initial rotation from about 4 hours to its current 15-hour period, the team said.
Zoom with a view: Made from two images taken 38 minutes apart, here is #UltimaThule! The "Thule" lobe is closest to the @NASANewHorizons spacecraft. As Ultima Thule is seen to rotate, hints of the topography can be perceived. @NASAhttps://t.co/fKsyLeW9pY pic.twitter.com/5S9zZ5d3Eg
— Johns Hopkins APL (@JHUAPL) January 3, 2019
6. Old and Primitive
“What we’re looking at is perhaps the most primitive object that has yet been seen by any spacecraft,” said Moore. MU69 is likely a cold classical Kuiper Belt object, a class of small bodies that are thought to be relatively untouched since the formation of the solar system, Protopapa said. “The term ‘cold’ does not refer to the objects’ temperatures, although they are very cold,” she said, “but refers instead to the primitive aspect of this population.” MU69 falls well within the average color and orbital tilt of this class.
7. Mostly Dark with a Shiny Necklace
“The light that we see on [the surface] is reflected from the Sun,” Olkin explained, “and we can see variations depending on how bright the surface is.” MU69’s reflectivity, or albedo, ranges from 13% at its brightest to 6% at its darkest. “This is like potting soil,” she said. The narrow neck contains some of the most reflective material on the object, Olkin explained, which may be a clue to the composition or grain size in that region.
My new sketch of @NewHorizons2015’s small Kuiper Belt object, #MU69! It’s a glimpse into the discussions going on behind the scenes: what do the shapes and colors mean and what geologic processes are at play? We will soon find out! @NASANewHorizons @JHUAPL #UltimaFlyby pic.twitter.com/4gyXY4forD
— James Tuttle Keane (@jtuttlekeane) January 3, 2019
8. No Atmosphere
Mission scientists do not expect MU69 to have an atmosphere or alter the flow of the solar wind in any measurable way, said Leslie Young, who is part of New Horizons’ atmospheric research team at SwRI. After the craft’s closest approach, it turned back toward MU69 to capture a backlit image of the object, which is how it measured the many layers of Pluto’s atmosphere in 2015. Initial data from the atmospheric dust, plasma, and ultraviolet instruments are in scientists’ hands and should be processed soon, Young said.
9. Ices Maybe?
“Our current theory as to why [MU69] is red is the irradiation of exotic ices,” Howett said. Alteration of methane, nitrogen, and carbon monoxide ices made much of the surface of Pluto and Charon’s north pole red. This theory, Protopapa warned, may not hold up on such a small object, which usually have surfaces covered with ammonia or water ice. The team does not expect to find exotic ices on MU69, Protopapa said, “but we will look for it and have the spectra