New Horizons Spots Possible Polar Ice Cap On Pluto

New Horizon image of Pluto and Charon via NASA/JHU-APL/SwRI

NASA's intrepid space explorer, New Horizons, has sent back teaser photos of Pluto as it draws ever closer to the ninth planet (I’m still in denial!). These photos, while only a few pixels in resolution, provide more detail on Pluto than ever before.

The largest circle in the photograph is Pluto and the smaller dot is Charon, Pluto’s largest moon. The photo might look unremarkable, but already it has uncovered mysteries about the dwarf planet's appearance.

In particular, there are regions of light and dark on Pluto. Scientists at NASA think that the bright area at 3 o’clock might be a polar cap. No matter which way the planet rotates, this region is always brighter. “It’s very suspiciously suggestive,” says Alan Stern, principal investigator on the mission.

Scientists speculate that this may be nitrogen ice instead of water ice like our polar caps. This is because telescopic observations of Pluto suggest it has a thin atmosphere made of nitrogen.

"It's rare to see any planet in the Solar System at this low resolution display such strong surface markings," said Stern. "Even if you had similar images of Mercury or even Mars, for example, you would not see the same kinds of big surface units as you do here on Pluto. And that's really promising for the imagery as we get closer and closer."

The camera we have to thank for these photographs is LORRI, or the Long-Range Reconnaissance Imager camera. The photograph exposure was only 1/10 of a second; not long enough to see Pluto’s four smaller moons in orbit. However, this camera is still warming up for the biggest performance of its life, starting on May 28th, 2015. At this time, LORRI will snap photos of Pluto every day as New Horizons moves closer toward the dwarf planet.  

The nearest photos will be on July 14, 2015. All the photos will be uploaded here so you can discover Pluto alongside New Horizons. Unfortunately, the spacecraft is moving too fast to enter Pluto’s orbit, so this will be our only chance to take detailed pictures.

These eagerly awaited photos have certainly been a long time coming; New Horizons was launched nine years ago. The space traveller is now a mere 13 million kilometers (70 million miles) away from Pluto—which is 5 billion kilometers (3 billion miles) from Earth for comparison.

"As we get closer, the excitement is building in our quest to unravel the mysteries of Pluto using data from New Horizons," says John Grunsfeld, associate administrator for NASA’s Science Mission Directorate.

Images of Charon's orbit around Pluto via NASA

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