<p>Our solar system makes makes a leisurely circuit every 250 million years around the galactic disk (above) of the <a href="http://ngm.nationalgeographic.com/2010/12/milky-way/croswell-text">Milky Way</a>. But the route is not straightforward; our sun dips in and out of the disk every 30 million years.</p> <p>Biologist Michael Rampino at New York University speculates that <a href="http://www.economist.com/news/science-and-technology/21644144-one-scientific-mystery-may-have-caused-another-did-dark-matter-do">this passage may be related to mass extinctions</a> on Earth—like the one that wiped out all dinosaurs except for birds 65 million years ago. Cometary impacts are one explanation, among several, scientists use to explain these mass extinctions.</p> <p dir="ltr">Disruptions—such as those caused by passing stars—in the Oort cloud, a debris field in the outer reaches of our solar system, can propel comets toward Earth. Rampino now believes that <a href="http://ngm.nationalgeographic.com/2015/01/hidden-cosmos/ferris-text">dark matter</a> can also rattle this cloud every time our solar system wanders through the galactic disk.</p> <p dir="ltr"><em>—By Jane J. Lee, photo gallery by Nicole Werbeck</em></p>

A Disruptive Disk

Our solar system makes makes a leisurely circuit every 250 million years around the galactic disk (above) of the Milky Way. But the route is not straightforward; our sun dips in and out of the disk every 30 million years.

Biologist Michael Rampino at New York University speculates that this passage may be related to mass extinctions on Earth—like the one that wiped out all dinosaurs except for birds 65 million years ago. Cometary impacts are one explanation, among several, scientists use to explain these mass extinctions.

Disruptions—such as those caused by passing stars—in the Oort cloud, a debris field in the outer reaches of our solar system, can propel comets toward Earth. Rampino now believes that dark matter can also rattle this cloud every time our solar system wanders through the galactic disk.

—By Jane J. Lee, photo gallery by Nicole Werbeck

Photograph by Royal Academy Sciences

Week's Best Space Pictures: A Giant Erupts, a Glacier Spills, and Janus Hovers

A volcano awakens after seven years, a river of ice and snow spills onto a plain, and a Saturnian moon hovers near some rings in this week's best space pictures.

Read This Next

The most ancient galaxies in the universe are coming into view
‘Microclots’ could help solve the long COVID puzzle
How Spain’s lust for gold doomed the Inca Empire

Go Further

Subscriber Exclusive Content

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet