A model of how craters were distributed, and their relative size, on the early Earth. The circle shows the size of the impact, while the colors show when they hit our planet. Credit: Simone Marchi/SwRI

In case you need a reminder that the solar system was a harsh place to grow up, the early Earth looks like it was in the middle of a shooting gallery in this model. The map that you see above shows a scenario for where researchers believe asteroids struck our planet about four billion to 4.5 billion years ago, which is very early in the Earth’s five-billion-year history.

The research reveals the surface of the Earth repeatedly being churned by these impacts as the young solar system came together, with small rocks gradually coalescing into planetesimals. Much of the leftover debris peppered the planets, including our own.

“Prior to approximately four billion years ago, no large region of Earth’s surface could have survived untouched by impacts and their effects,” stated Simone Marchi, who led the research and works at the Southwest Research Institute in Colorado.

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New Image of Rosetta’s Comet Reveals So Much More

by Jason Major on July 31, 2014

Comet 67P/Churyumov-Gerasimenko imaged by OSIRIS on July 29, 2014

Comet 67P/Churyumov-Gerasimenko imaged by OSIRIS’ NAC on July 29, 2014

WOW! We’re really getting to the good stuff now! This is no computer-generated shape model, this is the real deal: the double-lobed nucleus of Comet 67P/C-G, as imaged by Rosetta’s OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) narrow-angle camera on Tuesday, July 29. At the time just about a week away from making its arrival, ESA’s spacecraft was 1,950 km (1,211 miles) from the comet when this image was taken. (That’s about the distance between Providence, Rhode Island and Miami, Florida… that’s one fancy zoom lens, Rosetta!)

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If You Mine An Asteroid, Who Does The Property Belong To?

by Elizabeth Howell on July 31, 2014

An astronaut retrieves a sample from an asteroid in this artist's conception. Credit: NASA

An astronaut retrieves a sample from an asteroid in this artist’s conception. Credit: NASA

There have been several proposals in recent months to visit asteroids — NASA is talking about sending astronauts to an asteroid sometime, and both Planetary Resources and Deep Space Industries have outlined distant plans to mine these space rocks for resources.

But once the stuff is extracted, who does it belong to? A bill being considered by the U.S. House of Representatives says it would belong to “the property of the entity that obtained such resources.”

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What Are Comet Tails?

by Brian Koberlein on July 31, 2014

Comets are renowned for their big beautiful tails that stretch across the sky. But what’s in those things, anyway? And how can comets get multiple tails?
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It feels like a real stargazing session watching this video. You head out at dusk, waiting for the first few stars to emerge. Then there’s a moment when — if you’re in the right spot — whammo. The Milky Way pops out. The sky turns into a three-dimensional playground.

Combine that feeling with the Apollo 14 launch audio from 1971, and this timelapse is a lot of fun.

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