NASA has published the first high-resolution mosaic image of the surface of Pluto. In the image we see what New Horizons' principal investigator Alan Stern calls the "icy, frozen plains" of Pluto. It is made from three images that were taken by the LORRI imager on the New Horizons spacecraft at 6:10AM ET on July 14th, shortly before the spacecraft's closest approach. For scale, each pixel represents 0.4km on the surface.
One of the three frames in the mosaic shows a complex, frozen section of Pluto's surface that New Horizons geologist Jeff Moore jokingly called "not-easy-to-explain terrain" during a press conference. NASA is informally calling the region “Sputnik Planum” in honor of the first satellite to orbit the Earth. Sputnik Planum has an irregular, segmented surface separated by troughs, a pattern that's reminiscent of how mud dries on Earth.
In a zoomed-in view, Moore detailed what appears to be evidence of wind streaks on the surface. The dark streaks point in the same direction and stretch for miles. The icy surface also shows evidence of sublimation, a process where ice turns directly into gas. New Horizons scientists believe there may also be icy plumes on Pluto, perhaps from cyrovolcanoes, but there is still no visible evidence.
Another one of the frames in the mosaic was released at a press conference earlier this week. That lone image gave New Horizons team scientists a lot of new information about the dwarf planet. We now know Pluto has mountains made of water-ice that stretch as high as 11,000 feet, and that the surface is very young, which we know thanks to the telltale lack of visible impact craters.
These results are puzzling because, until this week, it was thought that icy bodies like Pluto were poorly equipped for geological activity. These types of worlds typically need a large source of gravity nearby (like Europa has with Jupiter) to provide the kind of tidal forces that can create surface features like the ones seen in these images. The New Horizons team will now focus some of its science efforts on figuring out why Pluto behaves this way.
Last week, Pluto was little more than a blurry speck in the sky. Now we're scouring it for the smallest details. But New Horizons team members are quick to remind everyone that there's more to come. The reconnaissance of Pluto is only going to expand, and the scientific analysis is going to get better. NASA has a few more landmark image releases planned in the coming days. The rest of the data from the spacecraft's flyby of Pluto will be unpacked, analyzed, and published over the next 16 months.