Asteroids Didn’t Create the Moon’s Largest Craters. Left-Over Planetesimals Did

The largest impact basin on the Moon is the South-Pole Aitken basin. It, and other impact basins, were created by planetesimals according to a new study. Image Credit: Moriarty et al., 2021.

The Moon’s pock-marked surface tells the story of its history. It’s marked by over 9,000 impact craters, according to the International Astronomical Union (IAU.) The largest ones are called impact basins, not craters. According to a new study, asteroids didn’t create the basins; leftover planetesimals did.

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InSight Felt the Ground Shake From a Meteorite Impact on Mars

Insight detected earthquake caused by impact that crated this crater.
Boulder-sized blocks of water ice lie around an crater blasted out by a meteoroid on December 24, 2021. NASA's InSight lander measured the earthquake the impact caused. Credit: NASA/JPL-Caltech/University of Arizona.

The Mars InSight lander might be nearing the end of its life on the Red Planet, but its scientific data are still shaking up the planetary science community. That’s because it detected another Marsquake on December 24, 2021. It was a major shaker and generated surface waves that rippled across the crust of the planet. The data from that quake allowed science team members to get a better idea of the Martian crust’s structure.

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Scientists Have Been Underestimating the Asteroid That Created the Biggest Known Crater on Earth

South Africa's Vredefort Crater is Earth's largest impact crater. New Research clarifies the power of the impact and its catastrophic effects. Image Credit: NASA Earth Observatory image by Lauren Dauphin / University of Rochester illustration by Julia Joshpe

Ancient impacts played a powerful role in Earth’s complex history. On other Solar System bodies like the Moon or Mercury, the impact history is preserved on their surfaces because there’s nothing to erase it. But Earth’s geologic activity has erased the evidence of impact craters over time, with some help from erosion.

Earth’s complex history has elevated its status among its Solar System siblings and created a world that’s rippling with life. Ancient giant impacts have played a role in that history, bringing catastrophe and disruption and irrevocably changing the course of events. Deciphering the role these giant impacts played is difficult since the evidence is missing or severely degraded. So how do scientists approach this problem?

One crater at a time.

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The Moon was Pummeled by Asteroids at the Same Time the Dinosaurs Died. Coincidence?

Earth and possibly its Moon were hit by impactors that killed off the dinosaurs
Artistic rendition of the Chicxulub impactor striking ancient Earth, with Pterosaur observing. Could pieces of the same impact swarm have hit the Moon, too? Credit: NASA

It only takes a quick look at the Moon to see its impact-beaten surface. There are craters everywhere. Some of those impact sites apparently date back to the same time some very large asteroids were whacking Earth. One of them formed Chixculub Crater under the Yucatan Peninsula. That impact set in motion catastrophic events that wiped out much of life on Earth, including the dinosaurs.

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Would We Have Continents Without Asteroid Impacts?

An impact between a Mars-sized protoplanet and early Earth is the most widely-accepted origin of the Moon. Did smaller impacts seed the formation of continents? (NASA/JPL-Caltech)

Early Earth was a wild and wooly place. In its first billion years, during a period called the Archean, our planet was still hot from its formation. Essentially, the surface was lava for millions of years. Asteroids bombarded the planet, and the place was still recovering from the impact that formed the Moon. Oceans were beginning to form as the surface solidified and water outgassed from the rock. The earliest atmosphere was actually rock vapor, followed quickly by the growth of a largely hot carbon dioxide and water vapor blanket. Earth was just starting land masses that later became continents. For decades, geologists have asked: what started continental formation?

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You can see Where JWST Took a Direct hit From a Micrometeorite on one of its Mirrors

Artist conception of the James Webb Space Telescope. Credit: NASA GSFC/CIL/Adriana Manrique Gutierrez

The world is still reeling from the release of the James Webb Space Telescope‘s (JWST) first images. These provided a comprehensive overview of the kind of science operations that Webb will conduct over its 20-year mission. They included the most sensitive and detailed look at some iconic astronomical objects, spectra from an exoplanet atmosphere, and a deep field view of some of the most distant galaxies in the Universe. Since their release, we’ve also been treated to glimpses of objects in the Solar System captured by Webb‘s infrared instruments.

Meanwhile, the JWST collaboration released a full report titled titled “Characterization of JWST science performance from commissioning,” in which they examined everything Webb has accomplished so far and what they anticipate throughout the mission. This paper recently appeared online and covers everything from the telescope’s navigation and pointing to the performance of its many instruments. An interesting tidbit, which was not previously released, is how Webb suffered a series of micrometeoroid impacts, one of which caused “uncorrectable change” in one mirror segment.

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A Chunk of Space Junk Just Hit the Far Side of the Moon

The Moon contains more metal than previously thought, according to a new study. Is it time to re-think the giant impact hypothesis? Image Credit: NASA / GSFC / Arizona State University

Observers have been tracking a chunk of space junk, waiting for it to strike the Moon. It should’ve hit the far side of the Moon, and hopefully, orbiters will have images of the impact site, though that might take a while.

The origins of the junk are in dispute. Some say it’s a spent booster from a Chinese rocket. Others say it’s from a SpaceX rocket. So far, nobody is claiming it.

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