Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

What makes Mars magnetic?

13.08.2007
Earth's surface is a very active place; its plates are forever jiggling around, rearranging themselves into new configurations. Continents collide and mountains arise, oceans slide beneath continents and volcanoes spew. As far as we know Earth's restless surface is unique to the planets in our solar system. So what is it that keeps Earth's plates oiled and on the move?

Scientists think that the secret lies beneath the crust, in the slippery asthenosphere. In order for the mantle to convect and the plates to slide they require a lubricated layer. On Mars this lubrication has long since dried up, but on Earth the plates can still glide around with ease.

If you could pick up a rock from the surface of Mars, then the chances are it would be magnetic. And yet, Mars doesn't have a magnetic field coming from its core. These rocks are clinging to the signal of an ancient magnetic field, dating back billions of years, to the times when Mars had a magnetic field like Earth's.

So how have these rocks hung onto their magnetic directions and what do they tell us about Mars? Strangely, the answer to these questions might be sitting here on Earth.

Most continental rocks on Earth align their magnetic moments with the current magnetic field - they are said to have 'induced' magnetism. "I consider induced rocks to have 'Alzheimers'. These are the rocks that forgot where they were born and how to get home," explains Suzanne McEnroe from the Geological Survey of Norway at a European Science Foundation (ESF), EuroMinScI conference near Nice, France this year.

However, not all of Earth's continental rocks have an induced magnetization. Some rocks stubbornly refuse to swing with the latest magnetic field, and instead keep hold of the direction they were born with. These rocks are said to have a remanent magnetization.

McEnroe and her colleagues have been studying some of Earth's strongest and oldest remanent magnetic rocks, to find out why they have such good memories. Understanding these rocks may give us clues as to what kind of rocks lie on Mars.

One of their research projects (in cooperation with Phil Schmidt and David Clark at CSIRO, Australia and just published in the Journal of Geophysical Research) is on the Peculiar Knob Formation in South Australia. These rocks are around 1 billion years old and have a strong magnetic remanence, more than 30 times larger than typically found in basaltic rocks.

"This particular research evolved from looking for an economic mineral deposit," says McEnroe. The mining company had assumed that the rocks in this strongly magnetic area were holding an induced magnetic field and that there would be magnetite buried down below. However, they were puzzled when a different mineral - hematite, came out of the drill core. Had they missed their target, or were their assumptions wrong?

By studying the samples under a powerful microscope and modelling their magnetic properties, McEnroe was able to show that the hematite was responsible for the strong magnetic field and that it was holding a remanent field from around 1 billion years ago. "We could see that the hematite contained small intergrowths that carried the magnetism," says McEnroe, who presented her findings at the 1st EuroMinScI Conference near Nice, France in March this year.

And it turns out that the microstructure of the rock is the key to whether it can hold a remanent magnetization or not. Together with Richard Harrison, a mineral physicist at Cambridge University, UK, and Peter Robinson at NGU, McEnroe has been studying strong remanent magnetic rocks from a variety of places including Scandinavia and the USA.

A study on nearly billion-year-old rocks in Norway showed a remanent magnetic anomaly comparable in scale to those observed on Mars. The remanent magnetic anomaly dominates the local magnetic field to such a degree that more than half the Earth's field is cancelled. It is nearly impossible to use a compass in the area, which cannot point correctly north because of the strong remanent magnetization in the rocks.

What they have found is that rocks containing nanometre scale intergrowths of ilmenite and hematite are better able to cling onto their original magnetization than those without such fine-scale features. "Placing a nanoparticle of ilmenite into the hematite host creates a strong and stable magnetic signal that can survive large changes in temperature and magnetic field over billions of years," explains Harrison.

So can this tell us anything about the rocks on Mars? "These rocks are good analogues for the magnetic rocks we see on Mars because of their strong magnetism and the length of time they have retained this memory," says McEnroe. Certainly this nano-scale microstructure is a plausible candidate for the magnetic rocks on Mars.

However, the rocks on Earth can't answer all our questions. "There is not going to be one mineral or one tectonic setting on Mars. There are going to be different reasons that enhance the signature in different places," says McEnroe. The only way to definitively answer the question is to go and pick up some rocks from Mars.

EuroMinScI is the European Collaborative Research (EUROCORES) Programme on "European Mineral Science Initiative" developed by the European Science Foundation.

Thomas Lau | alfa
Further information:
http://www.esf.org

More articles from Earth Sciences:

nachricht First evidence of surprising ocean warming around Galápagos corals
22.02.2018 | University of Arizona

nachricht World's first solar fuels reactor for night passes test
21.02.2018 | SolarPACES

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Stiffness matters

22.02.2018 | Life Sciences

Magnetic field traces gas and dust swirling around supermassive black hole

22.02.2018 | Physics and Astronomy

First evidence of surprising ocean warming around Galápagos corals

22.02.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>