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Understanding the Faint Young Sun Paradox

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Since the mid-1960s, scientists have argued about an apparent contradiction in our understanding of the early years of planet Earth. At issue was the overwhelming evidence for a warm Earth in its first billion-ish years, alongside evidence that the Sun would have been something like 25% dimmer then than it is today. How could Earth be warm if our star was dim? This is known as the faint young sun paradox.

One possible explanation has to do with greenhouse gases, and that's what Carl Sagan and George Mullen suggested in 1972. Over the decades since, multiple models have been developed that could explain the contradiction, though it's hard to be certain which (if any) of our current theories is correct.

In the short video below, MinuteEarth digs into the problem. Have a look:

If video isn't your thing, this National Geographic article is a good summary.

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Courtesy of Gem Diamonds Ltd.
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This Just In
Fifth Largest Diamond in The World Discovered in Southern Africa
Courtesy of Gem Diamonds Ltd.
Courtesy of Gem Diamonds Ltd.

The Letšeng diamond mine in the southern African nation of Lesotho is known for producing large, high-quality gems. As Bloomberg reports, a massive diamond uncovered there recently is the mine's most impressive yet. The 910-carat stone is roughly the size of two golf balls and weighs more than a billiard ball.

The diamond is thought to be the fifth largest ever discovered on Earth. Gem Diamonds Ltd., the company behind the discovery, said in a statement [PDF] that the "exceptional top quality diamond is the largest to be mined to date and highlights the unsurpassed quality of the Letšeng mine."

Beyond its size, the diamond is also remarkable for its purity. The D color Type IIa status means there are little to no nitrogen atoms muddying its color. Though Gem Diamonds hasn't revealed their price, the diamond is likely worth a huge amount: up to $40 million, analyst Ben Davis tells Bloomberg.

That's a steep price, but it's nowhere near the highest ever paid for a diamond at auction. Rare colored diamonds tend to fetch the highest bids: In 2015, the Blue Moon diamond sold for $48.5 million, and in 2017 the Pink Star was auctioned off for $71.2 million, making it the most expensive diamond of all time.

[h/t Bloomberg]

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Space
Mysterious 'Hypatia Stone' Is Like Nothing Else in Our Solar System
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iStock

In 1996, Egyptian geologist Aly Barakat discovered a tiny, one-ounce stone in the eastern Sahara. Ever since, scientists have been trying to figure out where exactly the mysterious pebble originated. As Popular Mechanics reports, it probably wasn't anywhere near Earth. A new study in Geochimica et Cosmochimica Acta finds that the micro-compounds in the rock don't match anything we've ever found in our solar system.

Scientists have known for several years that the fragment, known as the Hypatia stone, was extraterrestrial in origin. But this new study finds that it's even weirder than we thought. Led by University of Johannesburg geologists, the research team performed mineral analyses on the microdiamond-studded rock that showed that it is made of matter that predates the existence of our Sun or any of the planets in the solar system. And, its chemical composition doesn't resemble anything we've found on Earth or in comets or meteorites we have studied.

Lead researcher Jan Kramers told Popular Mechanics that the rock was likely created in the early solar nebula, a giant cloud of homogenous interstellar dust from which the Sun and its planets formed. While some of the basic materials in the pebble are found on Earth—carbon, aluminum, iron, silicon—they exist in wildly different ratios than materials we've seen before. Researchers believe the rock's microscopic diamonds were created by the shock of the impact with Earth's atmosphere or crust.

"When Hypatia was first found to be extraterrestrial, it was a sensation, but these latest results are opening up even bigger questions about its origins," as study co-author Marco Andreoli said in a press release.

The study suggests the early solar nebula may not have been as homogenous as we thought. "If Hypatia itself is not presolar, [some of its chemical] features indicate that the solar nebula wasn't the same kind of dust everywhere—which starts tugging at the generally accepted view of the formation of our solar system," Kramer said.

The researchers plan to further probe the rock's origins, hopefully solving some of the puzzles this study has presented.

[h/t Popular Mechanics]

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