The lovely Perseids’ comet could end life on Earth

The Swift-Tuttle comet is the source of the lovely Perseid meteor shower each August. It’s also getting closer and closer, making it "the single most dangerous object known to humanity."

The Perseids are arguably the most famous annual meteor shower. Silently streaking across the mid-August heavens each summer, it’s a profound and beautiful event for anyone with a dark sky and the discipline to just. Keep. Looking. Up. The often-exquisite shooting stars come from a comet that’s drawing ever closer to Earth. Dangerously close, actually: Radio astronomer Gerrit Verschuur has called Comet 109P/Swift-Tuttle "the single most dangerous object known to humanity." Apparently, our inspiring, transcendent meteor shower may also be the harbinger of humanity’s doom, give or take a few thousand years.



Perseids, 2013 (Credit: Flicker user the very honest man)

Why Swift-Tuttle is such a threat

Swift-Tuttle passes through our solar system at a steep angle compared to the solar system’s planets every 133 years. It swings around the sun, and as it does, melts slightly, casting off a massive debris field of ice and rock that’s estimated to grow as wide as 10 million miles and with a length of more than 75 million miles. This stuff is what rains down on us at an average of 37 miles per hour each August as what astronomers call “fireballs.” NASA’s Paul Chodas says, “The debris is coming in faster than many other comets because it's a very elongated orbit … so that makes the show a little more spectacular because of the speed.”


Swift-Tuttle orbit (Credit: NASA/JPL)

What concerns scientists about Swift-Tuttle is that each time it passes Earth, it’s slightly closer. There’s not much change year to year, but over time it adds up. In 1992, it was 110 million miles away, but in 2126 it will be a mere fraction of that: 14.2 million miles. In 3044, it will be less than a million, a frighteningly small distance in galactic terms. Current calculations have us as probably safe until 4479, though each time Swift-Tuttle sheds materials near the sun, the comet gets just a bit smaller, and it’s possible that planetary gravitational effects will eventually alter its orbit.


Swift-Tuttle in 1992 (Credit: NASA)

And Swift-Tuttle is big, with a nucleus of 16 miles (26 km) across. It’s more than twice the size of the Chicxulub impactor, the asteroid believed to have wiped out the dinosaurs. The energy it releases could be 27 times greater than that extinction event. Astrophysicist and author Ethan Siegel writes in Forbes that a collision with Swift-Tuttle would "release more than one billion megatons of energy: the energy equivalent of 20,000,000 hydrogen bombs exploding all at once."


NASA visualization of Chicxulub impact.

History of Swift-Tuttle

Reports of visits by Swift-Tuttle go all the way back to 69 B.C, though Swift-Tuttle was officially discovered and named in 1862 by American astronomers Lewis Swift and Horace Tuttle, who both discovered it independently. The “P” in “109P” refers to it being a periodic comet. Giovanni Schiaparelli realized in 1865 that it was the source of the Perseid meteor shower.

How to watch the Perseids

The Perseids this year can be seen from August 9 through the 14th and are expected to be even more impressive—200 fireballs an hour—than usual, thanks to the pull of Jupiter. On the other hand, lunar light will get in the way early on the night of peak visibility August 11-12 as the moon is 63% illuminated in its waxing gibbous phase. Waiting until the moon sets and the constellation Perseus rises around 1 am, however, still provides a 3.5-hour optimal viewing window between 1 am and 4:20 am.

NASA’s Bill Cooke shared the best advice for catching the Perseids or any meteor shower this or any year with Space.com.

"Meteor-shower observing requires nothing but your eyes; you want to take in as much sky as possible. Go outside in a nice, dark sky, away from city lights, lie flat on your back and look straight up. [Take] your choice of beverage and snacks and things like that."

You should plan to spend at least a few hours skywatching — your eyes won’t even fully adapt to the darkness for about 30 minutes. As Space.com puts it, “most showers only reveal their splendor in time.” And Cooke points out, “You can't observe a meteor shower by sticking your head out the door and looking for five minutes.”

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New fossils suggest human ancestors evolved in Europe, not Africa

Experts argue the jaws of an ancient European ape reveal a key human ancestor.

Surprising Science
  • The jaw bones of an 8-million-year-old ape were discovered at Nikiti, Greece, in the '90s.
  • Researchers speculate it could be a previously unknown species and one of humanity's earliest evolutionary ancestors.
  • These fossils may change how we view the evolution of our species.

Homo sapiens have been on earth for 200,000 years — give or take a few ten-thousand-year stretches. Much of that time is shrouded in the fog of prehistory. What we do know has been pieced together by deciphering the fossil record through the principles of evolutionary theory. Yet new discoveries contain the potential to refashion that knowledge and lead scientists to new, previously unconsidered conclusions.

A set of 8-million-year-old teeth may have done just that. Researchers recently inspected the upper and lower jaw of an ancient European ape. Their conclusions suggest that humanity's forebearers may have arisen in Europe before migrating to Africa, potentially upending a scientific consensus that has stood since Darwin's day.

Rethinking humanity's origin story

The frontispiece of Thomas Huxley's Evidence as to Man's Place in Nature (1863) sketched by natural history artist Benjamin Waterhouse Hawkins. (Photo: Wikimedia Commons)

As reported in New Scientist, the 8- to 9-million-year-old hominin jaw bones were found at Nikiti, northern Greece, in the '90s. Scientists originally pegged the chompers as belonging to a member of Ouranopithecus, an genus of extinct Eurasian ape.

David Begun, an anthropologist at the University of Toronto, and his team recently reexamined the jaw bones. They argue that the original identification was incorrect. Based on the fossil's hominin-like canines and premolar roots, they identify that the ape belongs to a previously unknown proto-hominin.

The researchers hypothesize that these proto-hominins were the evolutionary ancestors of another European great ape Graecopithecus, which the same team tentatively identified as an early hominin in 2017. Graecopithecus lived in south-east Europe 7.2 million years ago. If the premise is correct, these hominins would have migrated to Africa 7 million years ago, after undergoing much of their evolutionary development in Europe.

Begun points out that south-east Europe was once occupied by the ancestors of animals like the giraffe and rhino, too. "It's widely agreed that this was the found fauna of most of what we see in Africa today," he told New Scientists. "If the antelopes and giraffes could get into Africa 7 million years ago, why not the apes?"

He recently outlined this idea at a conference of the American Association of Physical Anthropologists.

It's worth noting that Begun has made similar hypotheses before. Writing for the Journal of Human Evolution in 2002, Begun and Elmar Heizmann of the Natural history Museum of Stuttgart discussed a great ape fossil found in Germany that they argued could be the ancestor (broadly speaking) of all living great apes and humans.

"Found in Germany 20 years ago, this specimen is about 16.5 million years old, some 1.5 million years older than similar species from East Africa," Begun said in a statement then. "It suggests that the great ape and human lineage first appeared in Eurasia and not Africa."

Migrating out of Africa

In the Descent of Man, Charles Darwin proposed that hominins descended out of Africa. Considering the relatively few fossils available at the time, it is a testament to Darwin's astuteness that his hypothesis remains the leading theory.

Since Darwin's time, we have unearthed many more fossils and discovered new evidence in genetics. As such, our African-origin story has undergone many updates and revisions since 1871. Today, it has splintered into two theories: the "out of Africa" theory and the "multi-regional" theory.

The out of Africa theory suggests that the cradle of all humanity was Africa. Homo sapiens evolved exclusively and recently on that continent. At some point in prehistory, our ancestors migrated from Africa to Eurasia and replaced other subspecies of the genus Homo, such as Neanderthals. This is the dominant theory among scientists, and current evidence seems to support it best — though, say that in some circles and be prepared for a late-night debate that goes well past last call.

The multi-regional theory suggests that humans evolved in parallel across various regions. According to this model, the hominins Homo erectus left Africa to settle across Eurasia and (maybe) Australia. These disparate populations eventually evolved into modern humans thanks to a helping dollop of gene flow.

Of course, there are the broad strokes of very nuanced models, and we're leaving a lot of discussion out. There is, for example, a debate as to whether African Homo erectus fossils should be considered alongside Asian ones or should be labeled as a different subspecies, Homo ergaster.

Proponents of the out-of-Africa model aren't sure whether non-African humans descended from a single migration out of Africa or at least two major waves of migration followed by a lot of interbreeding.

Did we head east or south of Eden?

Not all anthropologists agree with Begun and his team's conclusions. As noted by New Scientist, it is possible that the Nikiti ape is not related to hominins at all. It may have evolved similar features independently, developing teeth to eat similar foods or chew in a similar manner as early hominins.

Ultimately, Nikiti ape alone doesn't offer enough evidence to upend the out of Africa model, which is supported by a more robust fossil record and DNA evidence. But additional evidence may be uncovered to lend further credence to Begun's hypothesis or lead us to yet unconsidered ideas about humanity's evolution.