What Would Happen if Comet Hartley 2 Hit Earth?

News reports on comets have been dominated the past few days by NASA’s flyby yesterday morning of the comet 103P/Hartley 2 and the subsequent close-up pictures.

Before the NASA craft got cozy, the comet made its closest approach by Earth on October 20, coming a mere 11 million miles (17.7 million kilometers) from our planet.

Hartley 2 was discovered in 1986 and has been calculated to have a 6.5-year orbit. But this is the first time since its discovery that the comet has swung so close to home—gravitational tugs from Jupiter usually throw Hartley 2 onto a more distant course.

Still, that comet got closer to Earth last month than our nearest planetary neighbor, Venus, and doesn’t that just make you wonder: What would happen if Hartley 2 slammed into North America?

Well, wonder no more. Scientists at Purdue University in Indiana and Imperial College London today released the latest, user-friendly version of their disaster calculator tool Impact Earth!


Just feed the tool a few parameters—size, density, speed, angle of approach—and the program spits out such delightful data as the resulting change in the tilt of Earth’s axis, the size of the crater, the magnitude of any potential tsunami, and whether people around you would have their clothing ignited by the blast of thermal radiation.

That last part depends on your distance from the impact site, which is part of the overall calculations.

You can tell the tool exactly how big your impactor should be, or you can pick from a drop-down menu of sample sizes. Options include a school bus, a humpback whale, London, the moon, and [handily enough] Hartley 2.

The best part is that the tool is more than just edutainment. Its creators say their calculations are scientifically accurate enough for NASA or the U.S. Department of Homeland Security to make use of the data, according to the Milwaukee Journal-Sentinal.

However, “the site is intended for a broad global audience because an impact is an inevitable aspect of life on this planet, and literally everyone on Earth should be interested,” co-creator Jay Melosh of Purdue told the Wisconsin newspaper.

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