Charon’s Red Cap at its North Pole? We Might Have an Answer

Pluto’s largest moon, Charon, started off as a beautiful, smooth red grape until someone came along, mostly peeled it, tried to smoosh it, then just gave up and walked away, leaving the poor moon to look like the absolute travesty that it is. Okay, so maybe that’s not exactly what happened, but Charon just looks like a mess and scientists want to know why. Never mind its smooshed equator, but what’s the deal with its red cap? Where did it come from and why is it red?

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Pluto’s Surface was Shaped by Ice Volcanoes

New Horizons mission scientists have determined that cryovolcanic activity most likely created unique structures on Pluto not yet seen anywhere else in the solar system. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Isaac Herrera/Kelsi Singer

For all of Earth’s geological diversity and its long history, the planet has never had ice volcanoes. But Pluto has. And that cryovolcanism has shaped some of the ice dwarf’s surface features.

The resulting structures are unique in the Solar System.

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Now We Know Why Pluto has These Strange Features on its Surface

In the center left of Pluto’s vast heart-shaped feature – informally named “Tombaugh Regio” - lies a vast, craterless plain that appears to be no more than 100 million years old, and is possibly still being shaped by geologic processes. This frozen region is north of Pluto’s icy mountains and has been informally named Sputnik Planum (Sputnik Plain), after Earth’s first artificial satellite. The surface appears to be divided into irregularly-shaped segments that are ringed by narrow troughs. Features that appear to be groups of mounds and fields of small pits are also visible. This image was acquired by the Long Range Reconnaissance Imager (LORRI) on July 14 from a distance of 48,000 miles (77,000 kilometers). Features as small as one-half mile (1 kilometer) across are visible. The blocky appearance of some features is due to compression of the image. Credits: NASA/JHUAPL/SWRI

After New Horizons made its close flyby of Pluto in July of 2015, scientists were astounded at the incredible closeup views of Pluto’s surface. One of the most intriguing and mysterious features was a bright plain inside the prominent heart-shaped feature on Pluto, called “Tombaugh Regio” (Tombaugh Region) named after Clyde Tombaugh, who discovered Pluto in 1930.

The region is composed of a broken surface of irregularly-shaped segments that appear to be geologically young because no impact craters are part of the terrain.

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New Horizons is Now 50 Astronomical Units Away From the Sun

Currently exploring the Kuiper Belt, New Horizons is just one of five spacecraft to reach 50 astronomical units, on its way out of the solar system and, eventually, into interstellar space. (Credit: NASA/Johns Hopkins APL/Southwest Research Institute)

As the New Horizons spacecraft hurtles out towards interstellar space, it has now reached an historical milestone. On April 17, 2021, New Horizons passed 50 astronomical units, or 50 times Earth’s distance from the Sun. It is just the 5th spacecraft to reach that distance, joining the Voyagers 1 and 2 and the Pioneers 10 and 11.

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Oumuamua is Probably Very Similar to Pluto, Just From Another Star System

Artist's Concept of Oumuamua. Credit: William Hartmann

In 2017, the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) made history with the detection of a mysterious object called Oumuamua (Hawaiian for scout). Unlike countless other small objects that Pan-STARRS had detected before, Oumuamua seemed to originate from beyond the solar system. The first known interstellar object detected in the solar system, Oumuamua, with its odd trajectory, strange shape, and unusual acceleration, led to a flurry of activity in the astronomical community and an avalanche of wild claims of extraterrestrial space ships from various fringes of the media. A pair of papers published by Alan Jackson and Steven Desch of Arizona State University earlier this month reveals the best fit model for the identity of our extrasolar visitor. No, it isn’t aliens, but it’s pretty spectacular. Oumuamua seems to be a shard of a Pluto-like planet from another solar system!

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Pluto has Snowcapped Mountains, But Why?

On the left, the region of "Cthulhu" near the equator of Pluto and on the right, the Alps on Earth. Two identical landscapes, created by very different processes. Image Credit: © NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute © Thomas Pesquet / ESA

We can thank NASA’s New Horizons spacecraft for opening our eyes up to Pluto’s complexity. On July 14th, 2015, the spacecraft came within 12,500 km (7,800 mi) of the dwarf planet. During the flyby, New Horizons was able to characterize Pluto’s atmosphere and its surface.

Among the things New Horizons saw was a region of snowcapped mountains.

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Sunrises Across the Solar System

Saturn’s upper atmosphere. Processed using calibrated narrow-angle near-infrared (CB3) and ultraviolet (UV3) and wide-angle red, green, and violet filtered images of Saturn taken by Cassini on November 17 2007. NASA/JPL-Caltech/SSI/CICLOPS/Kevin M. Gill.

Scientists have learned a lot about the atmospheres on various worlds in our Solar System simply from planetary sunrises or sunsets. Sunlight streaming through the haze of an atmosphere can be separated into its component colors to create spectra, just as prisms do with sunlight. From the spectra, astronomers can interpret the measurements of light to reveal the chemical makeup of an atmosphere.

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Pluto and Other Kuiper Belt Objects Started Out With Water Oceans, and Have Been Slowly Freezing Solid for Billions of Years

Far left: The New Horizons team informally named Pluto’s heart-shaped feature “Tombaugh Regio” in honor of astronomer Clyde Tombaugh, who discovered the dwarf planet. The bright expanse of the western lobe of Pluto’s “heart” is informally called Sputnik Planum. Above left: Pluto’s surface sports a remarkable range of landforms that have their own distinct colors, telling a complex geological and climatological story. Credit: Courtesy NASA / JHUAPL / SwRI Table of Contents page 2015 Annual Report Division: (15)

It seems unlikely that an ocean could persist on a world that never gets closer than 30 astronomical units from the Sun. But that’s the case with Pluto. Evidence shows that it has a sub-surface ocean between 100 to 180 km thick, at the boundary between the core and the mantle. Other Kuiper Belt Objects may be similar.

But time might be running out for these buried oceans, which will one day turn to ice.

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New Horizons is so Far From Earth That the Positions of the Stars Look a Little Different From its Perspective

Credit: NASA/JHUAPL

In July of 2015, the New Horizons spacecraft made history when it became the first robotic explorer to conduct a flyby of Pluto. This was followed by another first, when the NASA mission conducted the first flyby of a Kuiper Belt Object (KBO) on December 31st, 2018 – which has since been named Arrokoth. Now, on the edge of the Solar System, New Horizons is still yielding some groundbreaking views of the cosmos.

For example, we here on Earth are used to thinking that the positions of the stars are “fixed”. In a sense, they are, since their positions and motions are relatively uniform when seen from our perspective. But a recent experiment conducted by the New Horizons team shows how familiar stars like Proxima Centauri and Wolf 359 (two of the closest stars in our neighbors) look different when viewed from the edge of the Solar System.

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Astronomers Continue to Analyze Pluto’s Atmosphere

This image of Pluto taken by the New Horizons spacecraft shows the blue color of Pluto's high-altitude haze. Image: NASA/New Horizons.
This image of Pluto taken by the New Horizons spacecraft shows the blue color of Pluto's high-altitude haze. Image: NASA/New Horizons.

When NASA’s New Horizons spacecraft flew past Pluto, studying the atmosphere was a key scientific objective. Most of what we know about the ice dwarf came from that flyby. That happened in July 2015, but it took over 15 months to send all the data home, and it’s taking even longer to analyze it.

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