Five Pluto Secrets From New Horizons

Five Pluto Secrets From New Horizons

13/07/2016Written by Tamela Maciel

It’s been a year since New Horizons made its closest approach to Pluto. Here are five things that we have learned about this icy dwarf planet since then.

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mascot Telescope Right
Image Credit: NASA

On 14 July 2015, NASA’s New Horizons mission came within 7,800 miles of Pluto, making its closest approach to this icy dwarf planet at the edge of our Solar System.

While the visit was fleeting, New Horizons glimpsed many surprising and mysterious details of Pluto and its five moons that continue to be processed and unravelled today.

Here are five things that we have learned about Pluto in the past year.

1. Pluto is not boring

Image Credit:  NASA, ESA, and M. Buie

Image Credit: NASA, ESA, and M. Buie

Before New Horizons, the best images we had of Pluto were from the Hubble Space Telescope (right). The images revealed blurry dark and light patches on the surface of Pluto but many astronomers assumed that Pluto was an old, cratered, dead world with no active geology.

To their great surprise, Pluto is full of fresh activity and exotic geology ranging from heart-shaped glaciers of solid nitrogen with floating water icebergs to mountains of ice more than two miles high. Pluto may even boast one of the largest active volcanoes in the Solar System, spewing out ice not lava onto the frozen world.

“The big surprise is that Pluto turned out so surprising,” says Jeffrey M. Moore of NASA’s Ames Research Centre, speaking to the New York Times.

2. Pluto has a beating heart

2. Pluto has a beating heart
Image Credit: NASA/JHUAPL/SwRI

Speaking of fresh geology, Pluto’s iconic heart-shaped plain of nitrogen ice, dubbed Sputnik Planum, is a living, beating heart, boiling like a giant lava lamp.

This plain is about the same size as the United Kingdom and France combined, and dominates Pluto’s surface. “Sputnik Planum is one of the most amazing geological discoveries in 50-plus years of planetary exploration,” says New Horizons Principal Investigator Alan Stern of the Southwest Research Institute. The plain’s intricate cell-like features are created and kept fresh by ongoing ice convection that sees warmer pockets of nitrogen ice bubbling to the surface, then cooling and sinking again.

It is thought that lighter icebergs of water float on top of this churning glacier of solid nitrogen.

3. Pluto’s moon Charon burst at the seams

3. Pluto’s moon Charon burst at the seams
Image Credit: NASA/JHUAPL/SwRI

Pluto is locked in a tight dance with its largest moon, Charon, whose surface is also full of surprises.

Spanning half the moon is an enormous canyon, Argo Chasma, that is nearly twice as long as the Grand Canyon and perhaps boasts the highest cliffs in the Solar System.

This rift may have occurred at a time when Charon was younger and warmer and its icy surface literally burst at the seams.

4. Pluto’s small moons wobble sideways faster than expected

Pluto’s four smaller moons – Styx, Nix, Kerberos, and Hydra – are covered in water ice and rotate faster than expected, wobbling on their sides like slow-spinning tops. Their chaotic spins help confirm the idea that these moons are the by-product of a collision that also formed Pluto and Charon.

5. Pluto has hazy clouds

5. Pluto has hazy clouds
Image Credit: NASA/JHUAPL/SwRI

New Horizons was able to photograph Pluto as it was backlit by the Sun, revealing layers of hazy, nitrogen atmosphere and maybe even a few clouds.

Because Pluto is so cold (-229°C on its surface), gas molecules from its atmosphere don’t escape very quickly, but it seems that the atmosphere is even colder and more compact than expected.

Molecules like methane help create the hazy layers and may even snow down on Pluto’s mountain peaks.

What’s next? NASA has confirmed an extended mission for New Horizons that will bring it to 2014 MU69, a small Kuiper Belt object, on New Year’s Day 2019. So more surprises are in store from the icy outer regions of our Solar System.

Since New Horizons flew by Pluto last July, we’ve realised that Pluto is a living, breathing world, driven by an exotic ice geology that still holds many mysteries. It may not be a planet, but it’s certainly not boring.