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NASA's New Horizons mission is kicking off its climactic month of July with amazing views that clearly show Pluto's black spots and Charon's dark pole growing in the spacecraft's virtual windshield.
After traveling for nine years and 3 billion miles, the New Horizons probe is less than two weeks and 9.5 million miles (15.2 million kilometers) away from Pluto. Every day is bringing improvements in image size and quality. Images from the Long Range Reconnaissance Imager, or LORRI, show patterns of dark and light areas on Pluto — including that dark patch, which looks a lot like a racing stripe, and a series of spots.
"We don't know what the spots are," the mission's principal investigator, Alan Stern of the Southwest Research Institute, said in news release, "and we can't wait to find out."
In a Reddit "Ask Me Anything" chat session, New Horizons team member Amanda Zangari compared Pluto to Triton, a moon of Neptune. Researchers believe Triton was a cousin of Pluto's in the icy Kuiper Belt that happened to be captured in Neptunian orbit:
"Both Pluto and Triton have a dark equatorial region and bright poles. Among the team, we've been impressed at how much they match. Pluto's dark patch is quite different though. Triton's got geysers, plumes and cantaloupe terrain and not a lot of craters. We won't know if Pluto is like that until we get closer, but it's within the realm of possibility."
Zangari wrote that the biggest surprise was the appearance of a dark circle at one of Charon's poles:
"We all think this is hysterical, because Charon had a dark pole in the simulation we did of what the encounter would be like. It was also a surprise because Charon's rotational light curve (i.e. its pattern of light and dark) is very subtle, so while we knew Pluto was going to have dark spots, Charon very well could have been uniform."
All these features will become clearer over the next two weeks, leading up New Horizons' Pluto flyby on July 14, when the piano-sized spacecraft will come within 7,800 miles (12,500 kilometers) of the dwarf planet's surface.
In addition to the visuals, the team is getting better readings about Pluto's composition. This week, scientists announced that they have begun to detect methane on the surface.
"We already knew there was methane on Pluto, but these are our first detections," Lowell Observatory planetary scientist Will Grundy, who heads New Horizons' surface composition team, said in a NASA news release. "Soon we will know if there are differences in the presence of methane ice from one part of Pluto to another."
There'll be a steady drumbeat of pictures, videos and live events — including Pluto TV webcasts and a series of "Plutopalooza" presentations across the country. To find a Plutopalooza near you, check out the schedules from New Horizons as well as NASA's Museum Alliance and Solar Systems Ambassadors Program.
For regular updates on the mission, keep an eye on the @NewHorizons2015 and @NASANewHorizons Twitter accounts and the New Horizons and NASA web portals. We're also getting into the act with DailyPluto.com updates on Facebook.
Update for 8:50 p.m. ET: After an intense seven-week search, the New Horizons team has determined that there are no dust clouds, rings or other hazards standing in the way of the spacecraft's course through the Plutonian system. If there were, New Horizons would have had to change course to avoid running into something at 30,800 mph (49,600 kilometers per hour).
"We're breathing a collective sigh of relief knowing that the way appears to be clear," Jim Green, NASA's director of planetary science, said in a news release. "The science payoff will be richer as we gather data from the optimal flight path, as opposed to having to conduct observations from one of the backup trajectories."
Scientists had expected to spot at least one moon to add to Pluto's retinue of five, but nothing turned up. "Not finding new moons or rings present is a bit of a scientific surprise to most of us," Stern said.
But some of Pluto's tinier moons are showing up: One eagle-eyed enthusiast posted an annotated picture to UnmannedSpaceflight.com, highlighting the moons Nix and Hydra as almost invisibly dim spots on LORRI's latest images.