Mars magnetic field mystery explained

September 25, 2008

( -- So much attention has been paid to the similarities and differences between Earth and Mars that we often look to the ancient red planet for signposts in our own planet's future. A U of T physicist, whose work is published this week in the prestigious international journal Science, may have explained some key differences in the magnetic fields of the two planets.

On Mars, the magnetic fields frozen into surface rocks over four-billion-years-old provide a glimpse of an ancient era when the planet possessed a global magnetic field generated by motions in its fluid core.

"If Mars' past magnetic field generation process -- called a dynamo -- worked like Earth's does today, then we would expect similar magnetic field strengths in both the northern and southern hemispheres," said U of T Professor Sabine Stanley, lead author of the study.

"But Mars' crustal magnetic fields are strongest only in the southern hemisphere," she said.

This asymmetry in magnetic field strengths is correlated with another odd ancient crustal feature on Mars. The northern hemisphere crust is thinner and lower than the southern hemisphere crust. Possible explanations for this dichotomy include a giant low-angle impact in the northern hemisphere, or a large-scale hemispheric circulation pattern in Mars' mantle from which the crust formed. Both of these scenarios have implications for the temperature at the core-mantle boundary of Mars, making the northern boundary warmer than the southern boundary.

Stanley and colleagues from MIT and Brown University wondered if the crustal dichotomy formation process could also explain the hemispheric magnetic intensity differences.To investigate, they created a computer simulation for Mars' past dynamo that takes into account the hemispheric temperature differences imposed by Mars' mantle on the core. In the resulting simulation, strong magnetic fields were only generated in the southern hemisphere.

"It is encouraging when the solution to one problem also solves another problem," said Stanley. Previous hypotheses for the magnetic field asymmetry relied on processes that altered the northern hemisphere crust after Mars' dynamo died. "In our model, the proposed formation mechanism for the crustal dichotomy also explains the strange magnetic fields frozen into the rocks at that time."

The ancient magnetic field pattern also has implications for Mars' ancient atmosphere. It is difficult to explain the rapid loss of Mars' ancient atmosphere if the planet possessed a strong magnetic field at that time.

"Our model of Mars' past dynamo may help since the magnetic field would only be strong in the southern hemisphere. Atmospheric removal could still be efficient in the northern hemisphere," explained Stanley.

Provided by University of Toronto

Explore further: Jupiter's moon Europa

Related Stories

Jupiter's moon Europa

September 30, 2015

Jupiter's four largest moons – aka. the Galilean moons, consisting of Io, Europa, Ganymede and Callisto – are nothing if not fascinating. Ever since their discovery over four centuries ago, these moons have been a source ...

India launches first space observatory

September 28, 2015

India successfully launched on Monday its first high-tech telescopes into space to study the stars, as New Delhi seeks to take another major step in its ambitious and low-cost space programme.

The sun

September 28, 2015

The sun is the center of the Solar System and the source of all life and energy here on Earth. It accounts for more than 99.86% of the mass of the Solar System and it's gravity dominates all the planets and objects that orbit ...

The gas (and ice) giant Neptune

September 14, 2015

Neptune is the eight planet from our Sun, one of the four gas giants, and one of the four outer planets in our Solar System. Since the "demotion" of Pluto by the IAU to the status of a dwarf planet – and/or Plutoid and ...

Could we terraform the sun?

September 11, 2015

In the list of crazy hypothetical ideas, terraforming the sun has to be one of the top 10. So just how would someone go about doing terraforming our sun, a star, if they wanted to try?

Recommended for you

Perfectly accurate clocks turn out to be impossible

October 7, 2015

Can the passage of time be measured precisely, always and everywhere? The answer will upset many watchmakers. A team of physicists from the universities of Warsaw and Nottingham have just shown that when we are dealing with ...

The topolariton, a new half-matter, half-light particle

October 7, 2015

A new type of "quasiparticle" theorized by Caltech's Gil Refael, a professor of theoretical physics and condensed matter theory, could help improve the efficiency of a wide range of photonic devices—technologies, such as ...

Professor solves 140-year fluid mechanics enigma

October 7, 2015

A Purdue University researcher has solved a 140-year-old enigma in fluid mechanics: Why does a simple formula describe the seemingly complex physics for the behavior of elliptical particles moving through fluid?

Fusion reactors 'economically viable' say experts

October 2, 2015

Fusion reactors could become an economically viable means of generating electricity within a few decades, and policy makers should start planning to build them as a replacement for conventional nuclear power stations, according ...


Adjust slider to filter visible comments by rank

Display comments: newest first

3.3 / 5 (6) Sep 25, 2008
Why are we apparently assuming that Mars is "ancient" when compared to Earth? Shouldn't they be about the same "age"? I think this may be a fundamental flaw in the theory.
5 / 5 (3) Sep 25, 2008
Why are we apparently assuming that Mars is "ancient" when compared to Earth? Shouldn't they be about the same "age"? I think this may be a fundamental flaw in the theory.

The general consensus is that Earth and Mars ARE about the same age...

Ancient is only referring to the time that Mars had a strong magnetic field and a relatively thick atmosphere.

Whereas Earth still currently has both of those, Mars lost them in "ancient" times.
5 / 5 (4) Sep 25, 2008
Why are we apparently assuming that Mars is "ancient" when compared to Earth? Shouldn't they be about the same "age"? I think this may be a fundamental flaw in the theory.

If you are referring to the use of the word in the first sentence, I think that's just bad reportage. Generally though, Mars' surface is probably considered old in comparison to Earth's, simply because tectonics stopped so long ago.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.