THAT PLUTO PROBE JUST MIGHT SAVE THE EARTH / THE WALL STREET JOURNAL OP EDITORIAL

That Pluto Probe Just Might Save the Earth

It will give us new insights into planet-threatening comets, so humans won’t go the way of the dinosaurs.

By Michio Kaku

July 13, 2015 6:36 p.m. ET

         
The dwarf planet Pluto. Photo: Getty Images/NASA


Imagine shooting a rifle at a target 130 miles away and scoring a bull’s-eye. That is the remarkable achievement of NASA’s historic New Horizons mission to Pluto, the last major celestial body in the outer reaches of the solar system to be visited by NASA space probes. One chapter in the exploration of space is now ending.

A miracle of modern technology, the New Horizons probe will buzz by Pluto on July 14 at 30,800 miles an hour from a distance of 7,800 miles. Launched in 2006 and costing $723 million, it has traveled a staggering 3 billion miles in nine years. Pluto is so distant that a radio signal takes about nine hours to get there and back. From Pluto the sun appears to be a minor star, lost in the Milky Way.

The New Horizons spacecraft weighs 1,052 pounds, is about the size of a piano, and is crammed with scientific instruments that will give us the closest look at the surface and atmosphere of this distant object and answer a host of astronomical mysteries. New Horizons will send back historic pictures of Pluto and photograph Charon, the largest moon of Pluto, and four other moons discovered recently.

Pluto is fascinating because it is a space oddity that seems to break all the rules. It is the black sheep of the solar system. When discovered in 1930, Pluto caused a media sensation as the first planet to be discovered in the 20th century. The sensation was so great that Walt Disney DIS 1.38 % apparently decided to name a cartoon dog after it.

But the more astronomers studied the planet, the smaller and stranger it seemed. Pluto is so small that it only has one-sixth the mass of our moon. Its orbit is so elliptical that it travels inside the orbit of Neptune during part of its year.

For decades, Pluto gave astronomers headaches because it didn’t fit the tidy categories of astronomical bodies. This maverick was much too far from the sun to be considered part of the inner Rocky Planet belt (which contains Mercury, Venus, Earth and Mars). Farther out, compared with the Gas Giants (Jupiter, Saturn, Uranus, Neptune) Pluto is a mere speck. It actually has more in common with the outer Kuiper belt of comets, since they are small, beyond Neptune, and mainly made of ice and rock.

The last straw came in 2005, when an object slightly larger than Pluto (subsequently called Eris) was discovered beyond the orbit of Pluto, raising the possibility of scores of distant icy Pluto-size objects. This sparked an identity crisis that split the astronomical community and even sparked public debate. In a vote of the International Astronomical Union, Pluto was unceremoniously demoted from a planet and became a Kuiper-belt object, formally called a “dwarf planet.”

Even today, some rogue astronomers cling to the idea that Pluto is really the ninth planet. Alan Stern, leader of the New Horizons mission, believes that Pluto is really a planet.

But anything so distant and alien may cause many readers to ask: So what? Of what possible use could Pluto have for us? Is this the best way to spend tax dollars?

The answer is that Pluto could give us a wealth of information about the origin of the solar system. It is like a time capsule, a frozen remnant of our early solar system preserved for more than a billion years. For example, astronomers once believed that Pluto was a moon of Neptune that somehow escaped its gravity. A newer theory proposes that the Gas Giants can migrate in their orbits, once considered a heretical idea, and that the expansion of the orbit of Neptune pushed Kuiper-belt objects like Pluto into their present orbits.

Pluto is also important because the Kuiper belt is still poorly understood but may hold a key to ensuring the safety of Earth. Most of the time, comets in the Kuiper-belt orbit safely around the sun. But occasionally something nudges them from their orbit, and they come tumbling toward the inner solar system. If one of them struck our planet, it would be a catastrophe unequaled in human history.

One theory holds that a renegade Kuiper-belt object about 6 miles wide slammed into Mexico 65 million years ago, so altering the planet that dinosaurs became extinct. Unfortunately, the dinosaurs didn’t have a space program.

The information gleaned from the New Horizons mission to Pluto is thus essential: It will give us a better understanding of the solar system’s origin and the nature of Kuiper-belt objects, and it will give us new insights into comets that might one day hit the Earth.


Mr. Kaku is a professor of theoretical physics at the City College of New York and the author of “The Future of the Mind: The Scientific Quest to Understand, Enhance, and Empower the Mind” (Doubleday, 2014).