Sign up for our daily briefing

Make your busy days simpler with Axios AM/PM. 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 Axios Closer 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!

Stay on top of the latest market trends

Subscribe to Axios Markets for the latest market trends and economic insights. Sign up for free.

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 Axios Sports. 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 Axios Des Moines

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 Axios Tampa Bay

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!

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!

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Color-enhanced view of Mercury. Photo: NASA/JHU-APL/Carnegie

Scientists are pushing space agencies around the world to send dedicated missions to the small, relatively unexplored planet Mercury.

Why it matters: With its odd, huge core, magnetic field and unexplained chemistry, the planet is like nowhere else in the solar system.

  • "Mercury seems to be a bit of an oddball," planetary scientist Paul Byrne told Axios.

The big picture: NASA has long-dedicated many of its limited resources to studying Mars and the Moon from close range, effectively leaving planets like Mercury, Venus, Uranus and Neptune somewhat left behind.

  • NASA's MESSENGER mission, which ended in 2015, provided a wealth of data for scientists interested in Mercury, but it also left them clamoring for answers about the small planet's chemistry and composition.

What's happening: NASA is considering establishing an assessment group that will focus on bringing scientists focused on Mercury together and will help advocate for missions.

  • "This community was focused around MESSENGER for a long time and is currently self-organizing," Shoshana Weider, support scientist in NASA's Planetary Science Division, told Axios via email. "But it is important to the community, and to NASA, that we recognize ... the efforts and interests of these scientists.”
  • The European Space Agency and Japan Aerospace Exploration Agency launched the BepiColombo mission to Mercury last year. The two spacecraft in the mission should make it into orbit around the innermost planet in 2025.

Details: MESSENGER mapped Mercury's surface and also found that about 85% of the planet’s volume is taken up by a huge metal core.

  • The ratio of potassium and thorium on Mercury also suggests that the planet may have formed elsewhere in the solar system or there could be a flaw in the models used to explain planetary formation, BepiColombo scientist Johannes Benkhoff told Axios.
  • "We thought we could predict some of what Mercury would be like, and we were wrong, so we have to go back and [re-examine] some of our basic, fundamental knowledge about the solar system," planetary geologist Brett Denevi told Axios.

What's next: Some planetary scientists hope to convince NASA to send a rover or lander to Mercury in the 2030s to study the planet from its surface to get more information about the small world than an orbiter could.

  • Scientists working with NASA will soon begin a study of what would be needed for such a mission — technically and budget-wise.
The transit of Mercury

Monday's transit of Mercury gave millions of people the chance to see the smallest major planet in our solar system in much the same way that scientists spot worlds around other stars.

The big picture: Exoplanets — planets orbiting stars other than our Sun — can be detected when a star's light dips as the planet passes across the face of its star.

Details: Mercury's transits can illuminate its exosphere — the planet's extremely thin atmosphere — for telescopes.

  • "Sodium in the exosphere absorbs and re-emits a yellow-orange color from sunlight, and by measuring that absorption, we can learn about the density of gas there," NASA scientist Rosemary Killen said in a statement.
  • The Hubble Space Telescope is able to parse out some elements of exoplanetary atmospheres this way as well, by watching as the planets pass in front of their stars.
  • NASA's James Webb Space Telescope will investigate exoplanet atmospheres in even more detail after its expected launch in 2021.

ICYMI: Sorry, but transits of Mercury are relatively rare events. The next one is expected to occur in 2032.

Go deeper

Updated 10 mins ago - World

Fatal stabbing of British MP David Amess declared a terrorist incident

Police outside Belfairs Methodist Church in Leigh-on-Sea, England, on Oct. 15. Photo: John Keeble/Getty Images

Authorities have declared the death of David Amess a terrorist incident, hours after the Conservative Party lawmaker in the U.K. was fatally stabbed while meeting with local constituents in a church in eastern England on Friday.

The big picture: The Metropolitan Police has found "a potential motivation linked to Islamist extremism."

Biden: DOJ should prosecute those who defy Jan. 6 subpoenas

President Biden speaks with reporters at Bradley International Airport in Windsor Locks, Connecticut. Photo: Brendan Smialowski/AFP via Getty Images

President Biden said Friday that the Justice Department should prosecute those who defy subpoenas from the Jan. 6 select committee.

Why it matters: The president's remarks come one day after Donald Trump ally Steve Bannon failed to show up for a deposition before the committee.

Updated 2 hours ago - Politics & Policy

Bill Clinton hospitalized for non-COVID-related infection

Former President Bill Clinton. Photo: Win McNamee/Pool/AFP via Getty Images

Former President Bill Clinton was admitted to the University of California, Irvine Medical Center on Tuesday for a non-COVID-related infection, his spokesperson Angel Ureña said Thursday.

The latest: In an update on Friday, Ureña said Clinton's health indicators are "trending in the right direction, including his white blood count which has decreased significantly."