Sign up for our daily briefing

Make your busy days simpler with the Axios AM and PM newsletters. Catch up on what's new and why it matters in just 5 minutes.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Catch up on the day's biggest business stories

Subscribe to the Axios Closer newsletter for insights into the day’s business news and trends and why they matter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Sign up for Axios Pro Rata

Dive into the world of dealmakers across VC, PE and M&A with Axios Pro Rata. Delivered daily to your inbox by Dan Primack and Kia Kokalitcheva.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Sports news worthy of your time

Binge on the stats and stories that drive the sports world with the Axios Sports newsletter. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Tech news worthy of your time

Get our smart take on technology from the Valley and D.C. with Axios Login. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Get the inside stories

Get an insider's guide to the new White House with Axios Sneak Peek. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Catch up on coronavirus stories and special reports, curated by Mike Allen everyday

Catch up on coronavirus stories and special reports, curated by Mike Allen everyday

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Denver news?

Get a daily digest of the most important stories affecting your hometown with Axios Denver

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Des Moines news?

Get a daily digest of the most important stories affecting your hometown with the Axios Des Moines newsletter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Twin Cities news?

Get a daily digest of the most important stories affecting your hometown with Axios Twin Cities

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Tampa Bay news?

Get a daily digest of the most important stories affecting your hometown with the Axios Tampa Bay newsletter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Charlotte news?

Get a daily digest of the most important stories affecting your hometown with Axios Charlotte

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Nashville news?

Get a daily digest of the most important stories affecting your hometown with the Axios Nashville newsletter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Columbus news?

Get a daily digest of the most important stories affecting your hometown with the Axios Columbus newsletter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Dallas news?

Get a daily digest of the most important stories affecting your hometown with the Axios Dallas newsletter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Austin news?

Get a daily digest of the most important stories affecting your hometown with the Axios Austin newsletter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Atlanta news?

Get a daily digest of the most important stories affecting your hometown with the Axios Atlanta newsletter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Philadelphia news?

Get a daily digest of the most important stories affecting your hometown with the Axios Philadelphia newsletter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Chicago news?

Get a daily digest of the most important stories affecting your hometown with the Axios Chicago newsletter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Sign up for Axios NW Arkansas

Stay up-to-date on the most important and interesting stories affecting NW Arkansas, authored by local reporters

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top DC news?

Get a daily digest of the most important stories affecting your hometown with the Axios DC newsletter.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Saturn's rings cast a narrow shadow on the planet in a 2009 image from Cassini. Image: NASA / JPL / Space Science Institute

Shadows from Saturn's rings can affect the planet's atmosphere, according to an analysis of data collected by the Cassini-Hyugens spacecraft during its final dives into the gaseous planet's upper atmosphere earlier this year. The work was presented yesterday at the American Geophysical Union conference and will be published this week in the journal Science.

Why it matters: These are the first direct measurements of Saturn's ionsophere as opposed to remote sensing observations, study author William Kurth from the University of Iowa tells Axios. Much of our knowledge of other planets is based on that about Earth, with modifications to account for what we know to be different. By sampling the ionosphere of Saturn, Kurth says researchers can begin to check these modified theories. "An important outcome, though, is that the improved theories incorporating things we learn at other planets, should help us understand our own planet better than we do."

Sound smart: The ionosphere is an upper layer of a planet's atmosphere that is electrically charged by the Sun's ultraviolet radiation. Saturn's extends from 300 km - 5,000 km above its surface. (Earth also has one. Ditto Jupiter. It is where auroras occur. )

How it works: Ultraviolet radiation from the sun can separate an electron from an atom of hydrogen or helium, charging the ionosphere. Parts of the ionosphere in the shadow of Saturn's A- and B-rings have a lower density of free electrons than other regions, suggesting the rings may be blocking the Sun's UV radiation.

Yes, but: The shadows account for some of the variations Cassini measured, but not all, the researchers said. One possibility is ice particles from the rings may interact with electrons in the ionosphere in certain places during a so-called "ring rain." Another is winds may be blowing the particles or the UV radiation from the Sun itself may vary.

What's next: The researchers analyzed data collected from just one of Cassini's probes and from the first 11 of its 22 dives so there is more to be studied.

"This [Cassini] data set will eventually provide a deep understanding of the ionosphere and its interaction with the rings. These analyses will continue not only this year, but for decades to come," says Kurth. "New questions will come from these studies and provide the basis for possible return missions to the Saturnian system."

Go deeper

Pelosi announces bid for re-election ahead of 2022 midterms

House Speaker Nancy Pelosi (D-Calif.) announced her bid for re-election Tuesday, amid a deluge of other safe-seat Democrats announcing their retirements.

Why it matters: Pelosi’s announcement follows months of speculation — despite her denials — that she was preparing to leave Congress.

Scoop: Qatar emir to visit White House on Monday

The emir of Qatar, Tamim bin Hamad Al Thani, leaves the White House after meeting President Trump in 2019. Photo: Nicholas Kamm/AFP via Getty Images

The emir of Qatar will meet with President Biden at the White House on Monday to discuss Afghanistan as well as contingency plans to provide natural gas to Europe in the event of a Russian invasion of Ukraine, Axios has learned.

Why it matters: Europe's reliance on Russia for 40% of its natural gas is undermining Biden's attempts to coordinate "massive" sanctions to be imposed from both sides of the Atlantic if Russia invades. The White House wants Qatar to help ensure European countries can enforce tough sanctions without risking an energy crisis.

Biden: There won't be "American forces moving into Ukraine"

President Joe Biden told reporters Tuesday that he does not foresee U.S. troops moving into Ukraine.

Why it matters: Biden's comments come as tensions between Russia and Ukraine persist, and a Russian invasion of Ukraine appears increasingly likely.