Newly released, highly processed images of Pluto show light and dark regions of the dwarf planet — and what looks like a bright polar ice cap — spinning through the field of view for NASA's New Horizons spacecraft.
The pictures are arguably higher-resolution than the best views from the Hubble Space Telescope, said Alan Stern, principal investigator for the $728 million mission. And as New Horizons nears its July 14 flyby of Pluto and its moons, the view is only going to get better.
"These images ... were what I call my 'meet-Pluto' moment," Stern said. "As the principal investigator of the mission, seeing it go from a point of light to an actual place that we're approaching was actually a little bit emotional."
The pictures were taken over a period running from April 12 to 18, from a distance ranging between 69 million and 64 million miles. They show Pluto and the largest of its five known moons, Charon, circling each other in an orbital dance.
"This is really a binary system, and it's unlike anything we've flown a spacecraft to in human history," Stern told reporters during a Wednesday teleconference. Charon is still merely a point of light, but patches of light and dark could clearly be seen flickering on Pluto in an animated sequence.
Johns Hopkins University's Hal Weaver, who serves as New Horizons' project scientist, said the brightness fluctuated as light and dark patches rotated in and out of view. "That makes it look like Pluto's tumbling when it's really not," he told NBC News.
Polar cap in sight?
Stern pointed to a bright patch at about the 3 o'clock position on the dwarf planet's disk. "For now, we can only say that it's very suspiciously suggestive of a polar cap," he said. Observations between now and June should be able to confirm whether it's an ice cap, and what kind of ice it's made of.
Pluto is the first world of its kind to be explored up close. It's a world that's big enough for gravity to shape it into a differentiated ball, but small enough to co-exist with other objects on the solar system's frontier. That led astronomers to classify it as a dwarf planet in 2006, just months after New Horizons' launch.
Nine years later, planetary scientists are on the verge of studying Pluto's mottled layer of surface ice — which is made up of frozen nitrogen, methane and carbon monoxide. They plan to find out whether there are organic chemicals in the ice. They're likely to figure out why Pluto's composition is so different from that of Charon, which has a surface layer of water ice. They'll also study Pluto's thin atmosphere and dust environment.
New Horizons could discover additional moons of Pluto, and perhaps rings and ice volcanoes as well. "These discoveries really are first of a kind," John Grunsfeld, associate administrator of NASA's science directorate, told reporters.
High-tech tricks
Weaver said Pluto's disk currently takes up only about 4.5 pixels of detector area on New Horizons' Long Range Reconnnaissance Imager, or LORRI. To tease out the additional details, the New Horizons team combined multiple images and used an image-processing technique known as deconvolution.
Thanks to the high-tech tricks, "we're pulling out details about a month in advance of where we thought we would be originally," Weaver said. Stern said New Horizons can now outdo Hubble when it comes to image resolution, "but we're not yet as sensitive to faint objects as Hubble is."
In the weeks ahead, team members plan to produce far more detailed maps of the surface, and sharper Pluto-Charon animations in color. Stern said the color views should show Pluto to be a reddish world — "not a very deep red, but a light red." The brightness variations could be due to compositional or topological differences, he said.
LORRI's pictures are already showing up in New Horizons galleries maintained by NASA and the mission team's headquarters at Johns Hopkins University Applied Physics Laboratory. Images will be captured daily starting on May 28, and they should be released 48 hours after they're received on Earth, Weaver said. The view should improve dramatically in late June as New Horizons homes in on Pluto for the July 14 flyby.
The team expects to gather so much data during the flyby that it will take months to transmit it all back to Earth, from a distance of more 3 billion miles. After the data dump, the team plans to ask NASA to extend New Horizons' mission for several more years. That would make it possible to study yet another object in the icy ring of material known as the Kuiper Belt.