Remembering Comet Hale-Bopp's Unlikely Discovery

Philipp Salzgeber // CC BY-SA 2.0 via Wikimedia Commons

Comet Hale-Bopp was a sensation in the mid-1990s. It was visible to the naked eye for 18 months, shattering a nine-month record previously set in 1811. It inspired a doomsday cult, wild late-night radio theories about extraterrestrials, and plenty of actual science. But a year before it became visible to normal observers, two men independently and simultaneously discovered it in a coincidence of astronomical proportions.

On the night of July 22-23, 1995, Alan Hale was engaged in his favorite hobby: looking at comets. It was the first clear night in his area for about 10 days, so he decided to haul out his telescope and see what he could see. In the driveway of his New Mexico home, he set up his Meade DS-16 telescope and located Periodic Comet Clark, a known comet. He planned to wait a few hours and observe another known comet (Periodic Comet d'Arrest) when it came into view. To kill time, he pointed his telescope at M70, a globular cluster in the Sagittarius system.

Comet Hale-Bopp streaks through a starry night sky.
Comet Hale-Bopp streaks through the sky over Merrit Island, Florida, south of Kennedy Space Center.
George Shelton // AFP // Getty Images

Hale was both an amateur astronomer and a professional. His interest in spotting comets was actually the amateur part, thought it would make his name famous. Hale's day jobs included stints at JPL in Pasadena and the Southwest Institute for Space Research in Cloudcroft, New Mexico. But that night, peering at M70, he wrote, "I immediately noticed a fuzzy object in the field that hadn't been there when I had looked at M70 two weeks earlier." He double-checked that he was looking in the right place, and then started to get excited.

In order to verify that the fuzzy object wasn't something astronomers already knew about, Hale consulted his deep-sky catalogues and also ran a computer search using the International Astronomical Union's computer at Harvard University. Convinced that he had found something new, Hale fired off an email very early on the morning of July 23 to the IAU's Central Bureau for Astronomical Telegrams, telling them what he had found, along with detailed instructions on how to verify it themselves. Hale also tracked the object as it moved, until it moved out of view. It was definitely a comet, and it was definitely new.

Meanwhile, Tom Bopp was in Arizona, also hunting for comets. At the time, Bopp was working at a construction materials company in Phoenix, but he was also an accomplished amateur astronomer, with decades of experience observing deep-sky objects. That night, Bopp vas visiting the remote Vekol Ranch, 90 miles south of Phoenix, known as a great location for dark-sky viewing. He was with a group of friends, which was important because Bopp didn't actually own a telescope.

The Bopp group looked through their various telescopes, observing all sorts of deep-sky objects late into the night. Bopp's friend Jim Stevens had set up his homemade 17.5-inch Dobsonian reflector telescope and made some observations. Stevens finished an observation, then left his telescope to consult a star atlas and figure out what to aim at next. While Stevens was occupied, Bopp peered into Stevens's telescope and saw a fuzzy object enter the field of view, near M70. He called his friends over to have a look.

The Bopp group proceeded to track the fuzzy object for several hours, just as Hale was doing over in New Mexico. By tracking its movement relative to background stars, they (like Hale) concluded that it was a comet. When the comet left his view, Bopp drove to a Western Union and sent a telegram to the Central Bureau for Astronomical Telegrams. (For historical perspective, telegrams were extremely outdated in 1995, but technically they were still a thing.)

Brian Marsden at the Central Bureau received Bopp's telegram hours later, after getting a few followup emails from Hale with additional details. Comparing the times of discovery, Marsden realized that the two men had discovered the comet simultaneously. According to NASA, it was the farthest comet ever to be discovered by amateur astronomers—it was 7.15 Astronomical Units (AU) from our sun. That's 665 million miles. Not bad for a pair of amateurs, one using a homemade telescope!

The Central Bureau verified the findings and about 12 hours after the initial discovery, issued IAU Circular 6187, designating it C/1995 O1 Hale-Bopp. The circular read, in part: "All observers note the comet to be diffuse with some condensation and no tail, motion toward the west-northwest."

Four men smile, posing outdoors next to a large telescope at night.
Comet hunters (L to R): David Levy, Dr. Don Yeomans, Dr. Alan Hale and Thomas Bopp pose next to a telescope during a public viewing of the Hale-Bopp and Wild-2 comets.
Mike Nelson // AFP // Getty Images

Less than a year later, Comet Hale-Bopp came into plain view, and the rest is history. It was a thousand times brighter than Halley's Comet, which had caused a major stir in its most recent appearance in the 1980s. Comet Hale-Bopp will return, much like Halley's Comet, but it won't be until the year 4385. (And incidentally, it was previously visible circa 2200 BCE.)

10 Riveting Facts About Mars

Mars's dust storms can be global. In these images taken a month apart in 2001, the dust storm near the southern polar ice cap (left) soon enveloped the entire planet (right).
Mars's dust storms can be global. In these images taken a month apart in 2001, the dust storm near the southern polar ice cap (left) soon enveloped the entire planet (right).

Few celestial objects have fascinated humankind throughout history more than the Red Planet. For over a century, we've longed to know more about Mars and the beings that we speculated lived there. When NASA dispelled the notion of creatures scurrying along the rusty plains, it raised a more tantalizing prospect: that we might one day be the creatures that call Mars home.

Mental Floss spoke to Kirby Runyon, a researcher at the Johns Hopkins University Applied Physics Laboratory, and Tanya Harrison, the director of research for Arizona State University's NewSpace Initiative, to learn more about the place your kids might live one day.


It takes 687 Earth days for the Red Planet make its way around the Sun. A Mars day—called a sol—lasts 24.6 hours, which would be a nuisance for the circadian rhythms of astronauts (but not as bad as a day on Venus, which lasts 5832 hours).


Mars looks desert-hot—New Mexico with hazy skies, red because of its iron oxide soil—but is actually very cold, with a blistering hot sol being 70°F, and a cold sol a brisk -225°F. Its dust storms can be huge; in 2018, one storm grew so large that it encompassed the entire planet for more than a month. (You can see a similarly huge dust storm in the image above.)


Compared to Earth, Mars is a tiny Styrofoam ball, with a diameter just over half of ours and one-tenth of our mass. Its gravity will be an absolute nightmare for future colonists, at .38 that of their native planet. (That means a person weighing 100 pounds here would weigh just 38 pounds on Mars.)


You won't want to get a breath of fresh air on Mars unless you're trying to suffocate: Its atmosphere is 95.32 percent carbon dioxide, with a little nitrogen and argon thrown in. (Earth's atmosphere, by contrast, is mostly nitrogen and oxygen.) When you do try to take that single, hopeless breath, the tears on your eyeballs, saliva in your mouth, and water in your lungs will immediately evaporate. You won't die right away, but you'll probably want to.


They're called Phobos and Deimos, which translate to Fear and Dread, respectively. They're shaped like potatoes and don't exactly fill the evening sky: Standing on the Martian surface, Phobos would appear to be about one-third the size of Earth's moon; Deimos would look like a bright star.

Future human Martians will have to enjoy Phobos while they can. The tidal forces of Mars are tearing Phobos apart; in 50 million years, the big potato will disintegrate.

In the meantime, Phobos is one of the stepping stones NASA plans to take on its journey to Mars. No part of human exploration of the Red Planet is easy, and before we land on Mars (and then have to figure out how to launch back into space and somehow get back to Earth), it's vastly easier to land on Phobos, do a little reconnaissance, and then take off and return home. As a bonus, on the journey to Phobos [PDF], astronauts can bring along hardware necessary for eventual Martian settlement, making the ride a lot easier for the next astronauts.


The tallest mountain on Earth, Mount Everest, is 29,029 feet tall. Olympus Mons on Mars is over 72,000 feet in height, making it the tallest mountain by far on any planet in the solar system.

Olympus Mons isn't the only extraordinary Mars feature: Mountaineers might also want to check out NASA's trail map for hiking the famous Face on Mars. If canyons are more your speed, you'll want to visit Valles Marineris. It is the size of North America and, at its bottom, four miles deep. (In the solar system, only Earth's Atlantic Ocean is deeper.) Once Earth's ice caps finish melting, you can always visit the ones on Mars. (If you have a telescope, you can easily see them; they are the planet's most distinctive features visible from your backyard.)


That's partially because of popular fiction (War of the Worlds, the 1897 novel by H.G. Wells, sees a Martian invasion force invade England) and partially because of Percival Lowell, the famed astronomer who wrote prolifically on the canals he thought he was observing through his telescope, and why they might be necessary for the survival of the Martian people. (Mars was drying up.)

Though it's easy to dismiss such conclusions today, at the time Lowell not only popularized space science like few others, but left behind the Lowell Observatory in Flagstaff, Arizona—one of the oldest observatories in America and the place where Clyde Tombaugh discovered Pluto.


Today, scientists work tirelessly to unlock the complex geologic history of Mars, to determine whether life exists there today, or did long ago. "We think that Mars was most globally conducive to life around 3.5 to 3.8 billion years ago," Runyon tells Mental Floss. "In the Mars geologic history, that's the end of the Noachian and toward the beginning of the Hesperian epochs." There may once have been a hemispheric ocean on Mars. Later, the world might have alternated between being wet and dry, with an ocean giving way to massive crater lakes. Where there's water, there's a good chance of life.

"If we found life on Mars—either extinct or current—that's really interesting," says Runyon, "but more interesting than that, is whether this life arose independently on Mars, separate from Earth." It is conceivable that meteorite impacts on Earth blasted life-bearing rocks into space and eventually to the Martian surface: "A second life emergence on Mars is not just a geological question. It's a biogeochemical question. We know that Mars is habitable, but we haven't answered the question of whether it had, or has, life."


Mars hasn't hurt for missions in recent years, though scientists now warn of an exploration desert beyond 2020. But that doesn't mean we humans don't have eyes on the planet. Presently in orbit around the planet are the Mars Reconnaissance Orbiter, which images and scans the planet; MAVEN, which studies its atmosphere; Mars Express, the European Space Agency's first Mars mission; MOM, the first Mars mission by the Indian Space Research Organization; the ESA's ExoMars Trace Gas Orbiter, which is searching for methane in the Martian atmosphere; and Odyssey, which studies Mars for water and ice signatures, and acts as a communications relay for vehicles on the ground.

Rolling around on the Martian surface are Curiosity and Opportunity—NASA missions both—which study Martian geology. Though the Russians and Europeans have tried mightily to do so, NASA is the only space agency to successfully land spacecraft on the Martian surface (seven times).

In November 2018, the InSight mission will land on Mars, where it will study the planet's interior. In 2020, NASA will land the Mars 2020 rover; where Curiosity studies Mars for signs of habitability, Mars 2020 will look for inhabitants.

"It is going to collect samples that will hopefully be brought back to Earth," says Runyon. "The three landing sites selected for Mars 2020 are Northeast Syrtis, Jezero Crater, and Columbia Hills within Gusev Crater, which is where the dead rover Spirit is currently sitting. Each of these sites is a hydrothermal environment dating from the Noachian-Hesperian boundary. These are some of the most perfect places to look for past signs of Martian life, and can help answer the question of whether life had a second genesis on Mars."


"Most people don't realize how active Mars is," Harrison tells Mental Floss. "Other planets aren't just these dead worlds that are frozen in time outside of our own. There are actually things happening there right now." Imagery from the HiRISE and Context Camera instruments on the Mars Reconnaissance Orbiter have revealed such events as avalanches, sand dune erosion [PDF], and recurring slope lineae (flowing Martian saltwater).

Things are moving, but it's not always clear why. "There's a lot of material that has been eroded away," says Harrison. "We have entire provinces of the planet that look like they've been completely buried and then exhumed. And that's a lot of material. The big question is, where did it all go? And what process eroded it all away?" Curiosity might help answer the question, but to really understand the processes and history of the fourth rock from the Sun, we're going to need to send geologists in spacesuits. "You can't replace human intuition with a rover," Harrison says. "Looking at a picture on your computer is not the same as standing there and looking around at the context, stratigraphic columns, being able to pick up the rocks and manipulate them, take a hammer to things. So once humans land on the surface, it'll be kind of like the difference between what we knew about Mars from Viking and Mars Global Surveyor and then the revolution between Mars Global Surveyor and Mars Reconnaissance Orbiter. Our view of what we think happened on Mars is going to completely change, and we'll find out that a lot of what we thought we knew was wrong."

A version of this story ran in 2017.

See What Hurricane Florence Looks Like From Space

NASA via Getty Images
NASA via Getty Images

As Hurricane Florence continues to creep its way toward the Carolinas, it’s repeatedly being described as both "the storm of the century” and "the storm of a lifetime” for parts of the coastlines of North and South Carolina. While that may sound like hyperbole to some, Alexander Gerst—an astronaut with the European Space Agency—took to Twitter to prove otherwise with a few amazing photos, and issued a warning to “Watch out, America!”

According to the National Weather Service, “Hurricane Florence will be approaching the Carolina shores as the day progresses on Thursday. Although the exact timing, location, and eventual track of Florence isn't known, local impacts will likely begin in the afternoon hours and only worsen with time throughout the evening and overnight period.”

On Tuesday, Wilmington, North Carolina's National Weather Service took the warning even one step further, writing: "This will likely be the storm of a lifetime for portions of the Carolina coast, and that's saying a lot given the impacts we've seen from Hurricanes Diana, Hugo, Fran, Bonnie, Floyd, and Matthew. I can't emphasize enough the potential for unbelievable damage from wind, storm surge, and inland flooding with this storm.”

Gerst’s photos certainly drive that point home.