 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 spectral resolution to identify these ices,” she said.
10. Craters and Ridges
The first close-up of MU69 sent back was not at the right angle to show small-scale elevation changes from craters or ridges. Neither was the second. When the team combined the two, however, they were able to create a low-resolution stereographic image that shows some high and low reliefs.
“You see how narrow the neck is, and we also get a sense that bright spots may be associated with topographic lows,” said Paul Schenk, a New Horizons coinvestigator from the Lunar and Planetary Institute in Houston, Texas. “This may indicate downslope movement of material from topographic highs like ridges. This may be an indication that the dark striping materials might be topographic ridges.” More images will refine these stereographic views and test these theories, he said.
20 Months of Data Ahead
Astronomers still have a long list of questions about MU69 that they are looking to New Horizons to answer. Data from the encounter will take about 20 months to fully downlink from the spacecraft. Forthcoming higher-resolution data should answer the lingering questions about this distant object, the team expects.
Just days after the flyby, New Horizons is already more than 3 million kilometers past MU69. “The first exploration of a small Kuiper Belt object and the most distant exploration of any world in history is now history, but almost all of the data analysis lies in the future,” Alan Stern, principal investigator for New Horizons from SwRI, said during a press conference. “Those of us on the science team can’t wait to begin to start digging into that treasure trove,” he said.
—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer