Asked multiple times, Stern admitted that it sure looks like it snows on Pluto. But team member Fran Bagenal joked that it wouldn't be a good place for skiing because the snow would be too hard-packed.
Deputy Project Scientist Cathy Olkin described some of the features visible on the best single full-disk image of Pluto the spacecraft will return (though the image was compressed to send it back more quickly; the high-resolution version won’t make it to Earth for a few weeks). She pointed out at least three linear features located in Pluto’s north polar region, hummocky and mountainous terrain, craters, the bright region the team has nicknamed the “heart,” and the dark stuff that covers much of the planet’s equatorial region. Many of these features suggest Pluto has been geologically active in the not-too-distant past (a billion years or so), but the scientists have yet to find a smoking gun proving current activity.
Team members Bill McKinnon and Bonnie Buratti discussed the bright heart and the ices that cover the area. Both were quite surprised at how dynamic Pluto looks. Going into the encounter, McKinnon mentioned that many scientists thought Pluto would be a blander version of Neptune’s moon Triton. “But we were wrong — it’s like Triton on steroids.” They have looked for features resembling the “black smokers” that erupt on Triton but have yet to see any in the current lower-resolution data.
Both scientists also said they were impressed with the dark polar region on Charon. As McKinnon says: “The dark pole of Charon was a complete surprise to the science team.” This tarry-looking region appears to be the result of sunlight irradiating the combined ices of carbon monoxide, methane, and nitrogen.
False-color compositional images released in the afternoon shows the two worlds are truly complex. New Horizons Co-Investigator Will Grundy says the team is work as fast as possible to identify the different substances the data reveals on the two surfaces. Most intriguing at the moment, though, is that Pluto's "heart" shows two very different colored regions.
No doubt plenty more surprises await in the days, weeks, and months ahead. And one more grand celebration tonight, when New Horizons phones home.
Karri Ferron contributed to this story.