When Dawn spacecaft arrived at Ceres we were all baffled by the bright spots on the surface of dwarf planet. I asked our panel about their predictions what those bright spots might be. What fascinating things will New Horizons find when it arrives at Pluto?
Seth Shostak (Senior Astronomer and Director of the Center for SETI Research at SETI Institute)
No one knows what the bright spots on Ceres are, but my bet would be some sort of ice, producing a “specular reflection” that looks exceptionally bright. These objects contain a lot of water of course, and that water’s going to be frozen, so the ice hypothesis seems reasonable, if perhaps dull. Pluto is larger than Ceres, and consequently will have a greater amount of internal heat generated by the slow radioactive decay of substances in its interior. That heat could occasionally break through to the surface in the form of icy geysers, much as occurs on Saturn’s moon Enceladus. If so, the dead ice ball image many people have of Pluto could be enlivened by some real drama. It’s an unknown world, and in the unknown there’s always plenty of opportunity for surprise.
Fraser Cain (publisher at Universetoday.com, co-host of Astronomy Cast)
It’s important to understand that the spots look bright because the contrast on Ceres has been cranked up so high so they look like spots of light. But they’re really just about as bright as ice compared to the dark asphalt landscape of Ceres. And that’s what I think they are; nothing more than regions of ice on the surface of Ceres. Of course, that makes them incredibly interesting. Why are they just in craters? How did they form? Are they ancient, or are new ones forming all the time? The more time Dawn spends, the more we’ll learn, and I’m really glad the spacecraft made this journey in the first place.
The greatest part about all of these missions is the discovery of things we never expected. Just like the white spots on Ceres, New Horizons is going to find completely unexpected features on Pluto, which will have us all arguing until the next mission is sent to Pluto.
Andrew Rader (SpaceX engineer, MIT PhD, author)