NASA's New Horizons spacecraft is still 24 million miles and more than a month away from the dwarf planet Pluto, but the probe's pictures are already revealing a world that's more complicated than previously thought.

"They show an increasingly complex surface with clear evidence of discrete equatorial bright and dark regions — some that may also have variations in brightness," the mission's principal investigator, Alan Stern of the Southwest Research Institute, said Thursday in an image advisory. "We can also see that every face of Pluto is different, and that Pluto's northern hemisphere displays substantial dark terrains."

The brightest as well as the darkest regions, however, appear to be on the icy world's equator or just south of it. "Why this is so is an emerging puzzle," Stern said.

Like previously released pictures, the images taken between May 29 and June 2 show a bright area at one of Pluto's poles that scientists suspect is an ice cap. Some of the pictures make it look as if Pluto is non-spherical — but the scientists say that's just an illusion, caused by the intensive image processing as well as the wide variations in surface brightness.

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These four images were taken at different times during Pluto's rotational period of 6.4 days -- on June 2, June 1, May 31 and May 29, from left to right. The central longitudes are 17 degrees, 63 degrees, 130 degrees and 243 degrees, respectively. New Horizons' LORRI imager took the pictures at distances ranging from 31 million miles to 34 million miles. NASA / JHUAPL / SwRI

As New Horizons closes in for its climactic July 14 flyby, the pictures should get much better — and amateur image-processing gurus already are poring over the daily deliveries of raw images from the piano-sized spacecraft's Long Range Reconnaissance Imager, or LORRI. (Now you can, too.)

One picture that's been posted to the UnmannedSpaceflight.com discussion forum appears to show a dark streak dividing bright areas on Pluto's disk. Icelandic imaging whiz Björn Jónsson says it looks like an honest-to-goodness surface feature, and may hint at activity on the surface.

"Dark lines crisscrossing a disk! It's the discovery of canali on Pluto!" the Planetary Society's Emily Lakdawalla half-jokingly observed. "We have reached Schiaparelli-quality mapping of Pluto's surface!"

Lakdawalla said it's fitting that the first observations of Pluto's surface evoke enigmas from the early days of the exploration of Mars and Venus. "Fortunately, we need only wait a few weeks more to learn whether the line is an artifact built by an alien civilization to transport valuable liquids across the Plutonian surface — or if it's something else entirely," she wrote.

NASA has just laid out its schedule for briefings on the approaching flyby. The first NASA TV update is scheduled for 11:30 a.m. ET on June 16, with week-by-week updates planned for June 23 and 30, same time, same station. (But subject to rescheduling if necessary.)

The mission updates will come on a daily basis at 11:30 a.m. ET starting July 7. There'll be an extended series of briefings on July 13, the day before the flyby.

NASA TV coverage of the big day itself will start at 7 a.m. ET, with the moment of flyby marked at 7:49 a.m. The distance between Pluto and Earth is about 3 billion miles (5 billion kilometers) — and that means it'll take four and a half hours for signals to be transmitted from New Horizons back to NASA.

A special broadcast about the mission, "Phone Home," will be beamed out from New Horizons mission control at Johns Hopkins University Applied Physics Laboratory at 8 p.m. ET July 14. The mission team expects to get a preprogrammed signal confirming the spacecraft's health after the flyby at about 9:02 p.m. That'll set off the big celebration — and set the stage for months of follow-up data transmissions.

As a teaser for the good times ahead, a documentary about the mission and "The Year of Pluto" will make its debut at 10 a.m. ET Friday, online and on NASA TV. What mysteries will be unraveled in the next month or so? Stay tuned ...