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Until now, it's been thought that clouds on Mars don't move water in a way that allows snow to form but new mathematical models published in Nature Geoscience today suggest it is indeed possible for convection snowstorms to occur in the Martian atmosphere — at night.

Why it matters: Researching snow on Mars has been important to understanding water on the planet and the Martian climate. "There [are] a couple of holy grails in Mars science," Hanna Sizemore, an expert on ground ice on Mars at the Planetary Science Institute who wasn't involved in the research, told Axios. "One of them is life, biology, and one of them, which is linked to the first, is understanding the water cycle." The authors say their study shows snow precipitation may have "played a key role in forming tropical and mid-latitude glaciers on Mars."

Why it happens at night and not during the day: At night there's no sunlight shining on the clouds and the ice particles floating around, so they cool down. And when they cool down, they're denser and heavier, so they fall. During the day, they're a little stabler because "warm air is moving upward in convection, but the ice clouds are being warmed from above and no cooling can take place," Isaac Smith, who works with the U.S. SHARAD team, said. Since the clouds are neither cooling nor heating, the unstable layers that drive the snowstorms can't form.

"One of the reasons this wasn't understood earlier is because this is occurring at night. Our observational data is fairly limited to daytime observations," an expert on Mars' climate history , Nathaniel Putzig, said. "It's kind of hard to catch it in the act."

What's next: Nicholas Heavens from Hampton University suggested future research might try modeling different time periods on Mars to see if those different climate conditions persisted and could have resulted in snowfall to the surface to form glaciers. Ultimately, he notes the need for "more observations to firmly demonstrate that this is happening on Mars," not just a model.

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Updated 5 hours ago - World

Mexican President López Obrador tests positive for coronavirus

Mexico's President Andrés Manuel López Obrador during a press conference at National Palace in Mexico City, Mexico, on Wednesday. Photo: Ismael Rosas/Eyepix Group/Barcroft Media via Getty Images

Mexican President Andrés Manuel López Obrador announced Sunday evening that he's tested positive for COVID-19.

Driving the news: López Obrador tweeted that he has mild symptoms and is receiving medical treatment. "As always, I am optimistic," he added. "We will all move forward."

6 hours ago - Politics & Policy

Sarah Huckabee Sanders to run for governor of Arkansas

Sarah Huckabee Sanders at FOX News' studios in New York City in 2019. Photo: Steven Ferdman/Getty Images

Former White House press secretary Sarah Huckabee Sanders will announce Monday that she's running for governor of Arkansas.

The big picture: Sanders was touted as a contender after it was announced she was leaving the Trump administration in June 2019. Then-President Trump tweeted he hoped she would run for governor, adding "she would be fantastic." Sanders is "seen as leader in the polls" in the Republican state, notes the Washington Post's Josh Dawsey, who first reported the news.

Coronavirus has inflamed global inequality

Illustration: Aïda Amer/Axios

History will likely remember the pandemic as the "first time since records began that inequality rose in virtually every country on earth at the same time." That's the verdict from Oxfam's inequality report covering the year 2020 — a terrible year that hit the poorest, hardest across the planet.

Why it matters: The world's poorest were already in a race against time, facing down an existential risk in the form of global climate change. The coronavirus pandemic could set global poverty reduction back as much as a full decade, according to the World Bank.