• Ideas

Why Pluto Still Deserves Our Love

7 minute read
Ideas

Zócalo Public Square is a magazine of ideas from Arizona State University Knowledge Enterprise.

One of my first memories as a child in the in the 1950s was a discussion I had with my brother in our tiny bedroom in the family house in Bethlehem, Pennsylvania. We had heard in school about a planet called Pluto.

Pluto was the farthest, coldest, and darkest thing a child could imagine. We guessed how long it would take to die if we stood on the surface of such a frozen place wearing only the clothes we had on. We tried to figure out how much colder Pluto was than Antarctica, or than the coldest day we had ever experienced in Pennsylvania. Did the surface of Pluto have mountains, frozen ponds like the ones we loved to skate on, or acres of snow to play in and build snowmen?

Pluto—which famously was demoted from a “major planet” to a “dwarf planet” in 2006—captured our imagination in a way that even Mars (a possible abode of life) and glorious, ringed Saturn couldn’t. It was a mystery that could complete our picture of what it was like at the most remote corners of our solar system.

Photographing Pluto: This Is How New Horizons Works

New Horizons Jupiter Io
A montage of New Horizons' images of Jupiter and its volcanic moon Io, taken during the spacecraft's Jupiter flyby in early 2007. NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
New Horizons Io Europa
A montage of New Horizons' images of the crescents of Io and Europa taken March 2, 2007, about two days after New Horizons made its closest approach to Jupiter. NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
New Horizons Europa Jupiter
The icy moon Europa rising above Jupiter's cloud tops taken on Feb. 28, 2007, six hours after the spacecraft's closest approach to Jupiter.NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Jupiter's Moons: Family PortraitRelease Date: May 1, 2007Keywords: Callisto, crater, Europa, Galilean satellite, Ganymede, Io, Jupiter, LORRI, moon(s)This montage shows the best views of Jupiter's four large and diverse "Galilean" satellites as seen by the Long Range Reconnaissance Imager (LORRI) on the New Horizons spacecraft during its flyby of Jupiter in late February 2007. The four moons are, from left to right: Io, Europa, Ganymede and Callisto. The images have been scaled to represent the true relative sizes of the four moons and are arranged in their order from Jupiter.Io, 3,640 kilometers (2,260 miles) in diameter, was imaged at 03:50 Universal Time on February 28 from a range of 2.7 million kilometers (1.7 million miles). The original image scale was 13 kilometers per pixel, and the image is centered at Io coordinates 6 degrees south, 22 degrees west. Io is notable for its active volcanism, which New Horizons has studied extensively. Europa, 3,120 kilometers (1,938 miles) in diameter, was imaged at 01:28 Universal Time on February 28 from a range of 3 million kilometers (1.8 million miles). The original image scale was 15 kilometers per pixel, and the image is centered at Europa coordinates 6 degrees south, 347 degrees west. Europa's smooth, icy surface likely conceals an ocean of liquid water. New Horizons obtained data on Europa�s surface composition and imaged subtle surface features, and analysis of these data may provide new information about the ocean and the icy shell that covers it.New Horizons spied Ganymede, 5,262 kilometers (3,268 miles) in diameter, at 10:01 Universal Time on February 27 from 3.5 million kilometers (2.2 million miles) away. The original scale was 17 kilometers per pixel, and the image is centered at Ganymede coordinates 6 degrees south, 38 degrees west. Ganymede, the largest moon in the solar system, has a dirty ice surface cut by fractures and peppered by impact craters. New Horizons� infrared observations may prov
A montage of the best views of Jupiter's four "Galilean" satellites as seen by the Long Range Reconnaissance Imager (LORRI) on the New Horizons spacecraft during its flyby of Jupiter in late Feb. 2007. The four moons are, from left to right: Io, Europa, Ganymede and Callisto. The images have been scaled to represent the true relative sizes of the four moons and are arranged in their order from Jupiter.NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
New Horizons Jupiter Io Ganymede
The New Horizons LORRI took this 2-millisecond exposure of Jupiter on Jan. 24, 2007. The spacecraft was 57 million kilometers (35.3 million miles) from Jupiter, closing in on the giant planet at 41,500 miles (66,790 kilometers) per hour. At right are the moons Io (bottom) and Ganymede; Ganymede's shadow creeps toward the top of Jupiter's northern hemisphere. NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Pluto and Charon display striking color and brightness contrast in this composite image from July 11.
Pluto and Charon display striking color and brightness contrast in this composite image from July 11. NASA-JHUAPL-SWRI
Pluto nearly fills the frame in this image from the Long Range Reconnaissance Imager (LORRI) aboard NASA’s New Horizons spacecraft, taken on July 13, 2015, when the spacecraft was 476,000 miles (768,000 kilometers) from the surface. This is the last and most detailed image sent to Earth before the spacecraft’s closest approach to Pluto on July 14.
Pluto nearly fills the frame in this image from the Long Range Reconnaissance Imager (LORRI) aboard NASA’s New Horizons spacecraft, taken on July 13, 2015, when the spacecraft was 476,000 miles (768,000 kilometers) from the surface. This is the last and most detailed image sent to Earth before the spacecraft’s closest approach to Pluto on July 14.NASA/APL/SwRI

Pluto’s underdog discovery story is part of what makes it so compelling. Clyde Tombaugh was a Kansas farm boy who built telescopes out of spare auto parts, old farm equipment, and self-ground lenses. In 1928, he sent drawings of Jupiter and Mars to Lowell Observatory, a premier observatory in Flagstaff, Arizona, to ask for a job as an assistant. At first, the observatory rejected his request, but Clyde showed persistence, and eventually got a job.

The observatory’s founder, the astronomer Percival Lowell, believed there existed a planet beyond the orbit of Neptune, so Tombaugh’s task was to search among millions of stars for a moving point of light. He used a device called a blink comparator, which compared two photographs of the sky taken at different times, so that a moving target, such as a planet, could be seen flitting back and forth against a background of fixed stars.

On February 18, 1930, Tombaugh found Pluto. It was the first planet discovered by an American, and represented a moment of light in the midst of the Great Depression’s dark encroachment. The planet’s name, referencing the Greek god of the underworld, was suggested by an 11-year old British girl. (The cartoon dog was named later.)

For decades, Pluto thrived in its role as the ninth major planet of our solar system, even though it was tiny compared to the others (just one-fifth the diameter of Earth) and so far away (on average, about 3.6 billion miles from the sun and 1 billion miles from Neptune, its closest planetary “neighbor”).

But then, in 1992, two astronomers discovered another planet-like object beyond the orbit of Neptune. Six months later, they discovered a third object. It looked like Pluto might actually be a member of a sort of asteroid belt, similar to but way beyond one we’ve known about for a long time between the orbits of Mars and Jupiter.

At this point, the scientific community began to wonder whether the tiniest planet was going to keep its rarefied title. Would it suffer the same fate as Ceres, the first and largest asteroid discovered in 1801, which reigned as a planet for decades before it was demoted? Despite this concern, a core group of scientists and engineers, me included, was working on convincing NASA to send a probe to our solar system’s last unexplored planet.

By the turn of the millennium, dozens more objects beyond Neptune like Pluto had been discovered, including one that might even be larger than Pluto. So, in August 2006, the International Astronomical Union elected to demote the planet. It now shares its dwarf planet designation with Ceres and three other of the 1,200 bodies that have been located beyond Neptune, collectively known as “Kuiper Belt Objects.”

This demotion came just seven months after we’d successfully launched the NASA New Horizons spacecraft. When I heard this sad announcement, I felt as if I’d lost an old childhood friend.

But Pluto’s scientific interest to those of us on the New Horizons team didn’t diminish. The Kuiper Belt is still an interesting place: It’s populated by icy bodies that are remnants of the solar system’s formation 4.6 billion years ago. These are the building blocks of planets, and they are still around for us to examine.

The few clues scientists have been able to gather about Pluto so far are tantalizing. We know its surface contains ices composed of methane, nitrogen, carbon monoxide, and other compounds familiar to us. It has some very dark regions, but it also seems to have a bright polar cap, like on Earth. Its atmosphere is very thin, but it’s composed largely of nitrogen, like our own. And we believe Pluto’s largest moon, Charon, was formed the same way as our moon, by coalescing from the debris left over from a massive impact by a rogue body.

So, all of us scientists are hoping that the close-up looks we are finally getting now of this dwarf planet can tell us how the chaos that reigned at the beginning of the solar system could have created objects so similar and yet so foreign as Earth and Pluto.

It’s taken nine years of travel, but we’ll finally get within 7,800 miles of Pluto Tuesday. Our spacecraft will enable us to see features as small as a football field. I’ve been painstakingly observing Pluto through a large telescope for over 15 years, seeing what I think is frost moving around on its surface with the seasons. I hope to see it more clearly as the data come in.

As we bear down on Pluto, all of us scientists are just as curious as I was in my childhood bedroom, wondering what Pluto is like. Is its surface old and cratered, or does it have shifting polar caps like the Earth’s that indicate recent activity? Does it have volcanoes like Jupiter’s moon Io, plumes like Neptune’s moon Triton, or water geysers like Saturn’s moon Enceladus? Will it just be like the objects around it, or will it have some unique quality that earns back the special place it once had in everyone’s hearts?

Pluto is much more than something that is not a planet. It’s an underdog we’re still cheering for. It’s a reminder that there are many worlds out there beyond our own—that the sky isn’t the limit at all. We don’t know what kinds of fantastic variations on a theme nature is capable of making until we get out there to look.

Bonnie Buratti is a principal scientist at NASA’s Jet Propulsion Laboratory and a member of the New Horizons science team. She divides her time between New Horizons and Cassini, a mission currently in orbit around Saturn.

More Must-Reads from TIME

Contact us at letters@time.com

TIME Ideas hosts the world's leading voices, providing commentary on events in news, society, and culture. We welcome outside contributions. Opinions expressed do not necessarily reflect the views of TIME editors.