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Astronomers have found that the majority of meteorites that regularly fall into Earth's atmosphere today are the result of an asteroid collision that took place 466 million years ago. Using chemical analysis from rock samples around the world, the team discovered that before that colossal collision, Earth experienced impacts from many different types of meteorite, meaning that our planet's history with meteorites is far more complex than we thought. After examining the chemical makeup of these chrome-spinels, the team found that 34 percent of the pre-collision micrometeorites were primitive achondrites, a type of meteorite that only makes up 0.45 percent...

(PhysOrg.com) -- A new theory suggests the Moon was formed after a natural nuclear explosion in the Earth's mantle rather than after the impact of a massive object with the Earth, as previously thought. The problem with the impact hypothesis is that simulations calculate the Moon should be composed of 80% impactor and 20% Earth, whereas in fact the isotope ratios of light and heavy elements found in Moon rocks so far examined are virtually identical to those on Earth. The fission hypothesis is an alternative explanation for the formation of the moon, and it predicts similar isotope ratios in...

It's a classic image from every youngster's science textbook: a cutaway image of Earth's interior. The brown crust is paper-thin; the warm mantle orange, the seething liquid of the outer core yellow, and at the center the core, a ball of solid, red-hot iron. Now a new theory aims to rewrite it all by proposing the seemingly impossible: Earth has not one but two inner cores. The idea stems from an ancient, cataclysmic collision that scientists believe occurred when a Mars-sized object hit Earth about 4.45 billion years ago. The young Earth was still so hot that it was mostly...

Deep down, the moon may be more like Earth than scientists ever thought. A new moon-rock study suggests the satellite has an iron core... The moon's core could be a clue to its ancient origins, which have long puzzled astronomers. "Our moon is too big to be a moon," Taylor said. "It's huge compared to the moons we see around other planets, so it has always been suspected that there was something strange in its origin." ...Rock samples from NASA's Apollo 15 and Apollo 17 moon missions of the early 1970s have now shed more light on the moon's origins,...

Mesopotamian climate change Geoscientists are increasingly exploring an interesting trend: Climate change has been affecting human society for thousands of years. At the American Geophysical Union annual meeting in December, one archaeologist presented research that suggests that climate change affected the way cultures developed and collapsed in the cradle of civilization — ancient Mesopotamia — more than 8,000 years ago. Archaeologists have found evidence for a mass migration from the more temperate northern Mesopotamia to the arid southern region around 6400 B.C. For the previous 1,000 years, people had been cultivating the arable land in northern Mesopotamia, using natural rainwater...

In a new study reported in Nature, climate scientist Rob DeConto of the University of Massachusetts Amherst and colleagues elsewhere propose a simple new mechanism to explain the source of carbon that fed a series of extreme warming events about 55 million years ago, the Paleocene-Eocene Thermal Maximum (PETM), and a sequence of similar, smaller warming events afterward. "The standard hypothesis has been that the source of carbon was in the ocean, in the form of frozen methane gas in ocean-floor sediments," DeConto says. "We are instead ascribing the carbon source to the continents, in polar latitudes where permafrost can...

New Haven, Conn. — The Gondwana supercontinent underwent a 60-degree rotation across Earth’s surface during the Early Cambrian period, according to new evidence uncovered by a team of Yale University geologists. Gondwana made up the southern half of Pangaea, the giant supercontinent that constituted the Earth’s landmass before it broke up into the separate continents we see today. The study, which appears in the August issue of the journal Geology, has implications for the environmental conditions that existed at a crucial period in Earth’s evolutionary history called the Cambrian explosion, when most of the major groups of complex animals rapidly...

Present-day nautilus shells almost invariably show thirty daily growth lines (give or take a couple) between the major partitions, or septa, in their shells. Paleontologists find fewer and fewer growth lines between septa in progressively older fossils. 420 million years ago, when the moon circled the earth once every nine days, the very first nautiloids show only nine growth lines between septa. The moon was closer to the earth and revolved about it faster, and the earth itself was rotating faster on its axis than it is now. The day had only twenty-one hours, and the moon loomed enormous in...