Our planet hides its wounds well. This is really embarrassing, because evidence from previous asteroid impacts can help us better plan for the next devastating collision. In fact, James Garvin, chief scientist at NASA’s Goddard Space Flight Center, believes we may have misinterpreted traces of some of the most serious asteroid impacts to have occurred in the past million years.

If he’s right, the odds of being hit by something bad may be higher than current estimates suggest. As Garvin nicely put it during his recent presentation at the Lunar and Planetary Science Conference, “This would be on the verge of some serious shit.”

This most famous of the meteorite impacts – the one that killed the dinosaurs about 66 million years ago that punched a hole in the crust of what is now the Yucatan Peninsula – is notable for decimating life on Earth. It was a giant monster, 10 kilometers (about 6 miles) long, that crashed into our planet about 100 million years ago.

Even so, much smaller collisions could still shake up enough dust to cover the planet, potentially leading to years of famine. By some estimates, kilometer-wide asteroids fall on Earth’s surface with a stream of heat and dust, on average, every plus or minus 600,000 years. Of course, there is no timeline for such events, and forecasts are only as good as the data we use to make our forecasts.

While we can scan the sky for evidence of rocks large enough to potentially cause us a world of pain, the geological record is like a flowing tape of actual meteorite impacts stretching back in time. Unfortunately, this record is getting harder and harder to read because of Earth’s dynamic winds, waters, and tectonics that are constantly eroding its surface. Even later events can be difficult to interpret due to dust and biology buildup.

Garvin and his team used a new catalog of high-resolution satellite images to take a closer look at the weathered remains of some of the largest impact craters that have formed over the last million years to better estimate their true size.

According to their analysis, some of these craters have faint rings beyond what is normally thought to be their outer rim, making them larger than previously thought. For example, the Zhaminshin Depression, which is about 12 to 14 kilometers wide in Kazakhstan, is believed to have been formed by a 200 to 400 meter diameter meteorite impact that struck Earth about 90,000 years ago. Event in the style of “nuclear winter”.

However, this already massive event could have been even more devastating, actually leaving a crater close to 30 kilometers across, according to the new analysis. The rim diameters of three other large craters were also listed, all doubling or tripling in size. Assuming that objects up to kilometers in size fall from above every few thousand years, the implications are big.

While it’s fine to shake older models every once in a while, these newly discovered rings may not necessarily be shockwaves. Maybe it’s the rubble thrown by a blow to the ground in heavy rain. Or maybe they don’t represent anything important at all – just a ghost in the data.

Garvin isn’t sure if the debris fields will stay clean after years of weathering and erosion. But science does not progress on a single observation. This is a hypothesis worth discussing. While we’re busy building systems to prevent a major collision with an asteroid, there’s a good chance Earth’s path will be open for a while. One thing our planet doesn’t need are scars to hide.