Ancient Earth saw a huge spike in meteor impacts. It may be ongoing.

Ever since the sun was born around 4.6 billion years ago, the solar system has been a violent place. Like a pinball machine filled to the brim, our cosmic neighborhood was once packed with meteors, comets, and even baby planets crashing into each other, leaving scars in the form of impact craters.

Today, we know that space rocks of all shapes and sizes continue their jostling dance. But it’s not clear how the number of impacts has actually changed over time.

Now, researchers using data from a NASA moon probe report something startling in the journal Science: 290 million years ago, the rate of impacts on the moon—and thus, Earth—increased dramatically, and that onslaught has possibly not yet died down.

 
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What Happened to Earth’s Ancient Craters? Scientists Seek Clues on the Moon’s Pocked Surface

Where have Earth’s craters gone?

On Thursday, researchers presented results of a new technique suggesting that the pace of space rocks pummeling Earth and the moon used to be less frequent than it is now, but then doubled or tripled for reasons not yet explained.

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Planetary scientist says spacesuit issue shows ‘it’s hard to feel included’ for female astronauts

How did the size of a spacesuit on the space station suddenly become a problem? Ontario Science Centre planetary scientist Sara Mazrouei weighs in on NASA’s wardrobe malfunction and why this points to a broader issue about female astronauts.

 
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Moon’s craters reveal recent spike in outer space impacts on Earth

It has long been thought that as the solar system grows older and stodgier, the number of asteroids and comets colliding with Earth and other planets has steadily gone down. But a new study reveals what appears to be a dramatic 2.5 times increase in the number of impacts striking Earth in the past 300 million years.

Earth’s surface is dotted with impact craters from the past billion years, but old craters are rarer than younger ones, a bias attributed to the crust-eating churn of plate tectonics, volcanism, and erosion. By looking at the moon, which doesn’t deal with the same forces but faces the same bombardment, scientists can probe the past of both bodies.

Scientists used a thermal camera on NASA’s Lunar Reconnaissance Orbiter to examine the number of large, heat-retaining rocks in the moon’s craters; those rocks are eventually ground to dust by minute meteorite impacts. By looking at previously dated craters, these rocks have been established as a reliable dating technique—the more intact the rocks, the younger the crater.


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A study just published reveals the moon experienced a dramatic increase in cratering rates about 300 million years ago. This corroborates evidence of a similar increase in Earth impacts. The paper is: The Earth and Moon impact flux increased at the end of the Paleozoic Sara Mazrouei, Rebecca R.


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Learning Earth’s Impact History With Lunar Craters


Our moon formed about 4.51 billion years ago and it’s been pummeled by meteorites ever since, leaving behind the lunar craters you can see on the surface today. Recently, scientists curious to know how often those impacts occurred came up with a clever way of determining the age of the craters. They discovered that many of them are relatively young—that is, the moon got hit by space rocks a lot more recently and a lot more frequently than scientists once thought. Sara Mazrouei, planetary scientist at the University of Toronto joins Ira to discuss the new research, out in the journal Science this week, and what it could tell us about Earth’s crater history.

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Asteroid strikes 'increase threefold over last 300m years'


Researchers worked out the rate of asteroid strikes on the moon and the Earth and found that in the past 290m years the number of collisions had increased dramatically.

Before that time, the planet suffered an asteroid strike about once every 3m years, but since then the rate has risen to once nearly every 1m years. The figures are based on collisions that left craters at least 10km (6.2 miles) wide.