Solar wind whips up Mercury’s poles

U. MICHIGAN (US) — Sodium and oxygen particles kicked up by a blistering solar wind at Mercury’s poles are the primary components of the planet’s wispy atmosphere, according to data from NASA’s Messenger spacecraft.

The Fast Imaging Plasma Spectrometer (FIPS), made by scientists at the University of Michigan, has taken the first global measurements of Mercury’s exosphere and magnetosphere in an effort to better understand how the closest planet to the Sun interacts with its fiery neighbor.

The measurements, reported in Science, confirmed scientists’ theories about the composition and source of the particles in Mercury’s space environment that become charged in a mechanism that’s similar to the one that generates the Aurora Borealis on Earth.

Planet Mercury as seen from the Messenger spacecraft in 2008. (Credit: NASA)

“We had previously observed neutral sodium from ground observations, but up close we’ve discovered that charged sodium particles are concentrated near Mercury’s polar regions where they are likely liberated by solar wind ion sputtering, effectively knocking sodium atoms off Mercury’s surface,” says Thomas Zurbuchen, professor of atmospheric, oceanic and space sciences and aerospace engineering.

Earth and Mercury are the only terrestrial planets with global-scale magnetic fields. The solar wind is a squall of hot plasma, or charged particles, continuously emanating from the Sun.

Earth, which has a relatively strong magnetosphere, can shield itself from most of the solar wind. Mercury, which has a comparatively weak magnetosphere and is 2/3 closer to the Sun, is a different story.

“Our results tell us is that Mercury’s weak magnetosphere provides very little protection of the planet from the solar wind,” Zurbuchen says.

Studying Mercury’s magnetosphere and space environment helps scientist understand fundamental science about the Sun.

“We’re trying to understand how the Sun, the granddaddy of all that is life, interacts with the planets,” says Jim Raines, doctoral candidate and FIPS operations engineer.

“It is Earth’s magnetosphere that keeps our atmosphere from being stripped away. And that makes it vital to the existence of life on our planet.”

More news from University of Michigan:

Correction: The article originally stated Earth and Mercury are the only two magnetized planets in the solar system, and as such, can somewhat deflect the solar wind around them. That statement was changed to the following: “Earth and Mercury are the only terrestrial planets with global scale magnetic fields.”

chat8 Comments


  1. Paul

    “Earth and Mercury are the only two magnetized planets in the solar system”

    All the gas giant planets (from Jupiter to Neptune) have significant magnetic fields.

  2. R.Will

    “The Fast Imaging Plasma Spectrometer (FIPS), made by scientists at the University of Michigan,”

    My recollection is that some 30 students were involved in the design and construction of this instrument.

  3. Thomas Zurbuchen

    @Paul: Yes – Mercury and Earth are the only terrestrial planets with global scale magnetic fields. The giants have global scale B-fields. Also, Mars has crustal field. @R.Will: We had over 60 students involved in building and running FIPS. We also had three startups involved at multiple occasions and for multiple tasks.

  4. R.Will

    Thanks to Dr. Z. for the reply.

  5. Glenn

    Yes, you may make the distinction between global scale magnetic fields and global scale B-fields… but that statement will be easily misunderstood by the vast majority of the population. In my opinion you should think about rephrasing.

    I hate it when the media grabs statements like that out of context and make our scientific community look bad.

  6. Thomas Zurbuchen

    @Glenn – point well taken. I contacted our press people to try to rectify that. The one thing I will say, though, is that it is almost impossible to make press statements 100% accurate. I tried many different things, but usually people want to put their own spin on things. But, in this case, I did connect and ask for a change. We’ll see whether I am successful.

  7. Nicole Casal Moore

    @Glenn, @Thomas: We fixed this unfortunate error on our press release and in our University Record story, but didn’t get to Futurity yet. I’m reaching out right now.

  8. Futurity-Jenny Leonard

    Futurity noted the correction from the University of Michigan and indicated the change at the end of the article.

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