A new mystery currently has the New Horizon's science team abuzz as the probe plunges ever closer to the Pluto – what's the deal with the series of dark spots near the dwarf planet's equator? The huge, neatly arranged dots were revealed in the latest color images snapped by the NASA probe and the scientists are hopeful of learning more about their origins in the coming weeks.

"It’s a real puzzle—we don’t know what the spots are, and we can’t wait to find out," said New Horizons principal investigator Alan Stern of the Southwest Research Institute, Boulder.

What has the scientists particularly baffled is the orderly fashion the similarly-sized dots appear alongside the planet's equatorial line, which looks almost like Pluto has slipped on a giant pearl necklace in time for its photo shoot with New Horizon's imaging gear. NASA reports that each of the spots is around 300 mi (480 km) in diameter, around the size of the state of Missouri.

The New Horizons team produced the images by taking black and white images from the probe's Long-Range Reconnaissance Image (LORRI) and combining it with data gathered with the Ralph color imager.

Another exciting discovery reported in NASA's latest mission update relates to the state of Pluto's atmosphere. For some time it has been suspected that it would freeze onto the planet's surface, in effect disappearing before we ever got a chance to study it up close. But the team has now confirmed this not to be the case.

New Horizon's is now less than 9.5 million mi (15 million km) from the Pluto system. With more than nine years having passed since its departure from Earth, all onboard machinery remains in working order and ready to study the planet from as close as 7,750 mi (12,500 km) when it glides past on July 14.

Source: NASA

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