After a lull of several weeks, the downlinking of new data from the New Horizons spacecraft has begun, including stunning new images of Pluto and its largest moon, Charon, as well as a treasure trove of other scientific data. There is so much to come that it will take about one year to downlink everything from the spacecraft and send back to Earth. Those first amazing images of Pluto and its moons were only the beginning.
As it flew past Pluto on July 14, New Horizons stored tens of gigabits of data on its digital recorders. The first images and other data sent back during the flyby were only 5 percent of what the spacecraft actually obtained; the remaining 95 percent would start to be sent back several weeks later.
“This is what we came for – these images, spectra and other data types that are going to help us understand the origin and the evolution of the Pluto system for the first time,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute (SwRI) in Boulder, Colo. “And what’s coming is not just the remaining 95 percent of the data that’s still aboard the spacecraft – it’s the best datasets, the highest-resolution images and spectra, the most important atmospheric datasets, and more. It’s a treasure trove.”
While New Horizons didn’t enter orbit around Pluto, it was still able to collect an enormous amount of data during the flyby, which will take months to send back to Earth, and many years to analyze.
Pluto is so far away—more than 3 billion miles—that even at the speed of light, it takes the radio signals 4.5 hours to reach Earth.
Since late-July, New Horizons had only been sending back lower data-rate information collected by the energetic particle, solar wind and space dust instruments. But now, the spacecraft will resume sending back flyby images and other data. The massive downlink of new data began over the Labor Day weekend, showing the surface at resolutions as good as 400 meters (440 yards) per pixel.
“The New Horizons mission has required patience for many years, but from the small amount of data we saw around the Pluto flyby, we know the results to come will be well worth the wait,” said Hal Weaver, New Horizons project scientist from the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.
For the public in general, the most exciting data to be sent back are the images—closeup views of a world never seen before in detail until now. Today, the newest images have been published on the New Horizons website, and they are indeed beautiful. These are unprocessed pictures from the Long Range Reconnaissance Imager (LORRI) instrument on New Horizons. The entire collection is here, while the most interesting science ones, showing Pluto’s varied terrain, etc., are here. New images will now be posted to the website each Friday, starting tomorrow, Sept. 11.
The new images show an amazing variety of complex terrain on Pluto, astonishing for such a small, cold world so far from the Sun.
“Pluto is showing us a diversity of landforms and complexity of processes that rival anything we’ve seen in the Solar System,” said Stern. “If an artist had painted this Pluto before our flyby, I probably would have called it over the top – but that’s what is actually there.”
The images show Pluto to be a geologically active world, more so than had been thought possible not that long ago.
“The surface of Pluto is every bit as complex as that of Mars,” said Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging (GGI) team at NASA’s Ames Research Center in Moffett Field, Calif. “The randomly jumbled mountains might be huge blocks of hard water ice floating within a vast, denser, softer deposit of frozen nitrogen within the region informally named Sputnik Planum.”
The large icy plains of frozen nitrogen stand in stark contrast to the rugged mountains and older cratered terrain. The nitrogen ice appears to slowly flow across the surface, similar to glaciers on Earth. There are also interesting networks of valleys and there might even be fields of dark sand dunes, surprising for a world with such a thin atmosphere. The regions of chaotic-looking, jumbled mountains are similar to what has been seen on Jupiter’s moon Europa.
“Seeing dunes on Pluto – if that is what they are – would be completely wild, because Pluto’s atmosphere today is so thin,” said William B. McKinnon, a GGI deputy lead from Washington University, St. Louis. “Either Pluto had a thicker atmosphere in the past, or some process we haven’t figured out is at work. It’s a head-scratcher.”
The images of Pluto returned so far also show that Pluto’s thin atmosphere contains many layers, which create a beautiful twilight effect that softly illuminates the night side terrain near sunset.
“This bonus twilight view is a wonderful gift that Pluto has handed to us,” said John Spencer, a GGI deputy lead from SwRI. “Now we can study geology in terrain that we never expected to see.”
There is also a new higher-resolution version of the previously released image of Pluto’s largest moon Charon, showing in greater detail that this moon also has a complex geological history including tectonic fractures, smooth plains and mountains, as well as an unusual dark region at the north pole. This region is much redder in color than other terrain on the moon. Scientists are interested in what is causing that color difference. The main theory right now is that small amounts of Pluto’s atmosphere can be “shared” with Charon where it could become trapped at the very cold poles, between -433 and -351 °F (-258 and -213 °C) in winter. The reddish material is thought to be the same as what is found in Pluto’s atmosphere—nitrogen, methane, and carbon dioxide. When the pole moves back into warmer sunshine later, the ices would sublimate away, but the solar radiation would also create a new substance from them called a tholin, which would explain the reddish coloring.
Better images of some of Pluto’s smaller moons, Nix and Hydra, will also be released tomorrow.
New Horizons is now heading toward its next target, a much smaller object in the Kuiper Belt called 2014 MU69, which is about a billion miles past Pluto. If all goes well, New Horizons is expected to reach 2014 MU69 on Jan. 1, 2019.
New Horizons is currently more than 3 billion miles (5 billion kilometers) from Earth, and more than 43 million miles (69 million kilometers) beyond Pluto. More information about the mission is available here and here.
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