NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

We Reach Pluto Tomorrow! 10 Fast Facts About 'New Horizons'

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Tomorrow morning, July 14, at 7:49 am ET, the spacecraft New Horizons makes its closest approach to Pluto in history. We'll be nearer to Pluto than New York City is to Hong Kong. Over the coming months the spacecraft will return libraries of knowledge about the mysterious planet. Here are a few things you might not know about the extraordinary probe.

1. New Horizons is the fastest spacecraft ever launched.

In 2006, an Atlas V rocket blasted New Horizons into space. By its third separation stage, the spacecraft was traveling a shade under 10 miles per second. To give some idea of its speed, it took the Apollo astronauts three days to get to the moon. New Horizons reached the same distance in nine hours.

2. Jupiter’s gravity acted as a slingshot on the probe.

A “gravity assist” involves a spacecraft flying near a planet and using that planet’s gravity to change speed or direction, as if flung by a giant slingshot. Jupiter’s gravity hurled New Horizons an extra 9,000 miles per hour, ramping up its speed to 52,000 miles per hour. While traveling through the Jovian system, New Horizons gave its instruments a test run, capturing such never-before-seen phenomena as lightning near Jupiter’s poles.

3. It is carrying the ashes of the man who discovered Pluto.

In 1930, Clyde Tombaugh, an American astronomer at the Lowell Observatory, discovered the planet that was eventually named Pluto. Tombaugh died in 1997, and New Horizons is carrying a small amount of his ashes. When the probe eventually moves beyond the Kuiper Belt, Tombaugh's ashes will be the first to travel beyond our solar system. The probe also carries a CD-ROM containing the names of 434,000 people who signed up to have their names sent to Pluto.

4. Planetary scientists consider Pluto a “science wonderland.”

That’s how the team at Johns Hopkins University’s Applied Physics Laboratory, which operates the New Horizons mission for NASA, describes the Pluto system. In addition to mapping Pluto’s geology and morphology, and analyzing its atmosphere and weather, New Horizons will study Charon, Pluto’s largest moon. By orbiting around a common center of gravity, the two worlds make up the only “binary planet” in the solar system. This is the first time we can study a new planetary class known as “ice dwarf” (the other two in our solar system being terrestrial planets and gas giants).

5. The entire mission will use less power than two 100-watt bulbs.

The energy efficient spacecraft is powered by a radioisotope thermoelectric generator (RTG), a kind of plutonium power plant. Like a big thermos bottle, the spacecraft is wrapped in thermal blankets (the gold foil seen in photographs) to hold in the heat produced by the spacecraft’s electronics, keeping them at a stable temperature. Notably, the RTG doesn’t provide propulsion. The spacecraft is still flying on the speed created by the launch and Jupiter’s gravity assist.

6. Its data is transmitted to Earth at 2 kbps.

The spacecraft uses a giant dish antenna to communicate with NASA’s Deep Space Network. It’s no trivial effort, though; the beam is only 0.3-degrees wide and has to hit Earth from Pluto and, eventually, beyond. (Considering the distances involved, New Horizons is quite the sharpshooter.) It takes four hours for data to arrive at the spacecraft, and once the flyby is complete, the probe will need a full 16 months to send all the data home.

7. There is almost zero margin for error.

The numbers are astonishing: New Horizons has traveled 3 billion miles at approximately 31,000 miles per hour (currently) and, if all goes as planned, will hit a target just 200 miles across. Because of orbital mechanics, if it is 100 seconds off course, it will not be able to gather 100 percent of the desired scientific data. Think about that: 100 seconds off course from a travel time of 9.5 years. Now that’s precision.

8. New moons mean new dangers.

In 2011, New Horizons discovered a second moon orbiting Pluto (Kerberos), and a year later a third (Styx). That’s been both exciting and worrying. These moons lack the mass and gravity to keep debris caused by planetary collisions from flying into space, where they could potentially smash into New Horizons. Debris doesn’t have to be big to be a threat: a piece the size of a grain of rice could prove catastrophic to the probe. Think of a rock hitting your windshield. Now imagine if you were driving 31,000 miles per hour.

9. The USA is the first country to explore every planet in the solar system.

NASA has been the first to launch each spacecraft that has successfully visited every planet, starting with Mariner 2 in 1962. July 14 is also the 50th anniversary of the Mariner 4 mission to Mars, the first exploration of the red planet. New Horizons completes humanity’s reconnaissance of the classical solar system.

10. The New Horizons mission does not stop with Pluto.

Once the spacecraft passes Pluto, it will have enough power and propellant to continue into the Kuiper Belt, a gigantic zone of icy bodies and mysterious small objects orbiting beyond Neptune. These objects are the building blocks of Pluto and planets like it. The new course will take New Horizons one billion miles beyond Pluto.

Big Questions
What is Mercury in Retrograde, and Why Do We Blame Things On It?

Crashed computers, missed flights, tensions in your workplace—a person who subscribes to astrology would tell you to expect all this chaos and more when Mercury starts retrograding for the first time this year on Friday, March 23. But according to an astronomer, this common celestial phenomenon is no reason to stay cooped up at home for weeks at a time.

"We don't know of any physical mechanism that would cause things like power outages or personality changes in people," Dr. Mark Hammergren, an astronomer at Chicago's Adler Planetarium, tells Mental Floss. So if Mercury doesn’t throw business dealings and relationships out of whack when it appears to change direction in the sky, why are so many people convinced that it does?


Mercury retrograde—as it's technically called—was being written about in astrology circles as far back as the mid-18th century. The event was noted in British agricultural almanacs of the time, which farmers would read to sync their planting schedules to the patterns of the stars. During the spiritualism craze of the Victorian era, interest in astrology boomed, with many believing that the stars affected the Earth in a variety of (often inconvenient) ways. Late 19th-century publications like The Astrologer’s Magazine and The Science of the Stars connected Mercury retrograde with heavy rainfall. Characterizations of the happening as an "ill omen" also appeared in a handful of articles during that period, but its association with outright disaster wasn’t as prevalent then as it is today.

While other spiritualist hobbies like séances and crystal gazing gradually faded, astrology grew even more popular. By the 1970s, horoscopes were a newspaper mainstay and Mercury retrograde was a recurring player. Because the Roman god Mercury was said to govern travel, commerce, financial wealth, and communication, in astrological circles, Mercury the planet became linked to those matters as well.

"Don’t start anything when Mercury is retrograde," an April 1979 issue of The Baltimore Sun instructed its readers. "A large communications organization notes that magnetic storms, disrupting messages, are prolonged when Mercury appears to be going backwards. Mercury, of course, is the planet associated with communication." The power attributed to the event has become so overblown that today it's blamed for everything from digestive problems to broken washing machines.


Though hysteria around Mercury retrograde is stronger than ever, there's still zero evidence that it's something we should worry about. Even the flimsiest explanations, like the idea that the gravitational pull from Mercury influences the water in our bodies in the same way that the moon controls the tides, are easily deflated by science. "A car 20 feet away from you will exert a stronger pull of gravity than the planet Mercury does," Dr. Hammergren says.

To understand how little Mercury retrograde impacts life on Earth, it helps to learn the physical process behind the phenomenon. When the planet nearest to the Sun is retrograde, it appears to move "backwards" (east to west rather than west to east) across the sky. This apparent reversal in Mercury's orbit is actually just an illusion to the people viewing it from Earth. Picture Mercury and Earth circling the Sun like cars on a racetrack. A year on Mercury is shorter than a year on Earth (88 Earth days compared to 365), which means Mercury experiences four years in the time it takes us to finish one solar loop.

When the planets are next to one another on the same side of the Sun, Mercury looks like it's moving east to those of us on Earth. But when Mercury overtakes Earth and continues its orbit, its straight trajectory seems to change course. According to Dr. Hammergren, it's just a trick of perspective. "Same thing if you were passing a car on a highway, maybe going a little bit faster than they are," he says. "They're not really going backwards, they just appear to be going backwards relative to your motion."

Embedded from GIFY

Earth's orbit isn't identical to that of any other planet in the solar system, which means that all the planets appear to move backwards at varying points in time. Planets farther from the Sun than Earth have even more noticeable retrograde patterns because they're visible at night. But thanks to astrology, it's Mercury's retrograde motion that incites dread every few months.

Dr. Hammergren blames the superstition attached to Mercury, and astrology as a whole, on confirmation bias: "[Believers] will say, 'Aha! See, there's a shake-up in my workplace because Mercury's retrograde.'" He urges people to review the past year and see if the periods of their lives when Mercury was retrograde were especially catastrophic. They'll likely find that misinterpreted messages and technical problems are fairly common throughout the year. But as Dr. Hammergren says, when things go wrong and Mercury isn't retrograde, "we don't get that hashtag. It's called Monday."

This story originally ran in 2017.

science fiction
Why So Many Aliens in Pop Culture Look Familiar

Aliens have been depicted countless times in cinema, from Georges Méliès's A Trip to the Moon (1902) to James Cameron's Avatar (2009). But despite the advancements in special-effects technology over the past century, most aliens we see on screen still share a lot of similarities—mainly, they look, move, and interact with the world like humans do. Vox explains how the classic alien look came to be in their new video below.

When you picture an alien, you may imagine a being with reptilian skin or big, black eyes, but the basic components of a human body—two arms, two legs, and a head with a face—are likely all there. In reality, finding an intelligent creature that evolved all those same features on a planet millions of light-years away would be an extraordinary coincidence. If alien life does exist, it may not look like anything we've ever seen on Earth.

But when it comes to science fiction, accuracy isn't always the goal. Creating an alien character humans can relate to may take priority. Or, the alien's design may need to work as a suit that can be worn by human performers. The result is a version of extraterrestrial life that looks alien— but not too alien—to movie audiences.

So if aliens probably won't have four limbs, two eyes, and a mouth, what would they look like if we ever met them person? These experts have some theories.

[h/t Vox]


More from mental floss studios