Once upon a time, several billion years ago, Earth was pelted with giant asteroids and comets with horrifying frequency. These would-be worlds and distant ice balls can still pop into our planetary neighbourhood from time to time, but the era of frequent planetary pinball games looks to be over. In the eons since, massive impacts became less frequent, but every now and then a sizeable chunk of rock slammed into the Earth, giving it a brand-new scar.
The pits these momentous meetings of planet and space rock have left behind have often succumbed to erosion, but some still remain. The problem is that you wouldn’t often know you’re wandering into one of them because, well, civilisation happened and the raw earth was paved over. Fortunately, as spotted by Twitter user and space aficionado Jason Major (@JPMajor), there’s a website (click here!) that can lets you know if you live near one of these preserved rocky cauldrons.
The site appears to be perpetually under construction by its owner, Dr Robert Beauford (who studied meteorites and impact craters at the University of Arkansas), so its current listing is perhaps incomplete. The crater sites are also limited to those found in the United States. But this work-in-progress is nevertheless a fun resource. Check it out — it might alter your perspective when you realise you once drove through somewhere that was wrecked by a blast so powerful it makes the sum total of the entire country’s Fourth of July fireworks look laughable.
The Des Plains Impact Crater in Illinois is a great example. Around 280 million years ago, a rock the size of a small village smashed into what is now North America, digging out a hole five miles across. Today, that spot hosts the city of Des Plaines, home to 60,000 people.
You would think that such a profoundly prominent pit would be quickly noticed by anyone living there. But it’s actually invisible; it has no surface expression whatsoever, so it can’t even be seen from orbit. The crater was only discovered when drilling efforts dug up strange minerals and textures typically generated through impacts.
This stealthy quality is one shared by most of Earth’s impact craters. Some do stand out as plain as day, particularly if they were carved out of what is now an arid sandy desert and are geologically youthful (hello, Arizona’s Barringer impact crater). But many of the planet’s impact-related injuries can’t be found. That’s because, unlike the rest of the inner solar system’s members, Earth is excellent at burying its own past.
Earth has a decent and dynamic atmosphere, with strong winds; it has rivers, lakes, seas and oceans; it has plate tectonics, a mountain-making, basin-opening, crust-gobbling monster of a planetary artist; it has volcanoes that erupt fresh lava across its surface all the time; it has biology, which has had around four billion years to run rampant across every single facet of its surface. Mars, the Moon and Mercury lack all of these surface-erasing processes to any significant degree.
Venus is a bit of an odd one: it is shrouded in a thick atmosphere of nasty acid and carbon dioxide, which means we can’t see its surface very well. But a handful of orbital spacecraft have found almost all of it to be lacking in noteworthy number of craters. This is the consequence of a lot of volcanic eruptions that took place in the recent geological past: vast floods and rivers of lava that smothered lots of the planet’s older craters. Circumstantial evidence suggests that eruptions are almost certainly happening there today, but even if that is the case, Venus has weak winds, no flowing water, no surface life and no full-blown plate tectonics.
That’s why it takes so much effort, and plenty of sneaky scientific and technological wizardry, to find most of Earth’s ancient impact craters. Without question, our pale blue dot reigns supreme as the inner solar system’s geologic-redactor-in-chief.