Jun 8, 2017

Comets may have delivered some of Earth's atmosphere

ESA/Rosetta/NAVCAM, CC BY-SA IGO 3.0

Scientists have wondered for decades where xenon (the heaviest stable noble gas on Earth) came from. Now they have a partial answer: at least one-fifth of it in Earth's atmosphere may have originated in comets, a new study finds.

Eight of the nine different isotopes of xenon on Earth have been traced to different parts of the cosmos that came together as the planet and our solar system formed. But the source of the remaining xenon isotope was a mystery.

How they solved the mystery: Data collected by the Rosetta spacecraft, whose mission is to study a comet known as 67P, showed that xenon leaking from it had been trapped in the comet's icy surface from a time before our solar system was formed. It matched one of the isotopes of xenon on Earth that scientists had been unable to source – strongly suggesting it came from comets just like 67P.

What it means: If such a significant portion of xenon found in Earth's atmosphere came from comets, then it's also possible that comets raining down on our planet for millions of years also delivered other important materials, like water and the building blocks of life.

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Trump to install loyalist Ric Grenell as acting intelligence chief

Photo: Sylvain Gaboury/Patrick McMullan via Getty Images

President Trump confirmed in a tweet Wednesday night that he will install Richard Grenell, the current U.S. ambassador to Germany and a staunch defender of the president, as the acting director of national intelligence.

Why it matters: The role, which was originally vacated by Dan Coats in August 2019, is one of grave responsibility. As acting DNI, Grenell will be charged with overseeing and integrating the U.S. intelligence community and will advise the president and the National Security Council on intelligence matters that concern national security.

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What to watch in the Nevada debate

Photo Illustration: Eniola Odetunde/Axios. Photos: Cengiz Yardages and Mario Tama/Getty Images

Michael Bloomberg's wealth will fuel rather than shield him from tests and attacks when he makes his Democratic primary debate debut on the stage tonight in Las Vegas.

The state of play: Bernie Sanders is still the front-runner. So the other candidates must weigh which of the two presents a bigger threat to their viability: Sanders, with his combined delegate, polling and grassroots momentum? Or Bloomberg, with his bottomless budget?

Go deeperArrowUpdated 14 mins ago - Politics & Policy

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