Plate Tectonics May Have Once Operated On Mars, As Reported In The 30 April Issue Of Science

April 30, 1999

This news release is also available in French.

Washington DC - Mars may once have maintained a plate tectonics system, according to a team of U.S. and French scientists who have analyzed new magnetic information about the planet's crust. The team reports its findings, which may be the first direct evidence that plate tectonics are not unique to Earth, in two papers in the 30 April issue of Science.

"When the possibility of there once having been a plate tectonics system on Mars appeared in the data we were extremely excited. This interpretation has very interesting implications for our understanding of Mars and the other planets," said Henri Reme, of the Centre d'Étude Spatiale des Rayonnements at CNRS, in Toulouse, France, who is a member of the team.

Plate tectonics leave a distinctive magnetic signature in the Earth's crust, and it is this type of signature that scientists working with data from the Mars Global Surveyor spacecraft think they see in the oldest regions of crust on Mars. If confirmed, this would mean that many of the same forces that continue to form Earth's topography today may once have shaped Mars, before grinding to a halt.

When it emerged in the 1960s, the theory of plate tectonics revolutionized geologists' understanding of Earth just as the theory of natural selection illuminated evolution and the big bang theory transformed cosmology. Geologists began to agree that Earth's crust is divided into interlocking sections, or plates, that float atop the partially molten mantle. Heat from deep inside Earth's core drives a convection system within the surrounding mantle, causing the plates on the surface to shift like pieces of a restless jigsaw puzzle. As the plates separate, collide, and squeeze past each other, these motions form the basis for a unified explanation for a wide variety of geologic questions such as why earthquakes and volcanic eruptions occur, why and how mountain ranges form, and why ancient fossils and rocks from a seemingly common location have been found on disparate continents separated by miles of ocean.

What clinched the theory of plate tectonics on Earth was the presence on the Atlantic sea floor of a bar-code-like series of magnetic stripes. Scientists noticed that in each stripe, the crust's iron-bearing minerals aligned in the same direction, alternating between north and south. Intriguingly, these stripes formed symmetrical mirror images on either side of a ridge running down the center of the ocean basin. The now-standard explanation for this curious pattern is that the mid-ocean ridge is actually the site of sea-floor spreading, in which two tectonic plates diverge and allow magma to well up. As the magma cools to form new crust, its iron-bearing minerals magnetize and "freeze" in the direction of the prevailing magnetic field, which flip-flops north to south every 10,000 years or so. Such alternating, mirror-image magnetic stripes have become the definitive signature of plate tectonics on Earth.

The similarly patterned stripes on Mars are much more strongly magnetized than those on Earth, possibly because the martian crust is richer in iron. They are also much longer, some extending over 2,000 km in length, and about ten times wider, possibly because the spreading rate was much faster on Mars than on Earth, or because the magnetic field switched directions fewer times during the formation of new crust.

"We had no idea we'd see anything of this magnitude. It was mind blowing, really," said research team member Jack Connerney of NASA Goddard Space Flight Center in Maryland.

The researchers were also able to closely explore many other patches of magnetism elsewhere on Mars, in addition to the magnetic stripes that occur mostly in the southern hemisphere. They describe these features in a second paper in the same issue of Science.

Scientists have long been fascinated by the striking difference between Mars' two hemispheres. The northern hemisphere lies below Mars' mean surface level and is much younger than the elevated "highlands" of the southern hemisphere, which are heavily scarred with impact craters and wide channels. The team's findings suggest that the highlands might be remnants of early crust that was formed between two spreading plates. In some places the magnetic imprint may have been preserved, and in others it may have been demolished by later impacts and heating events such as volcanism.

The idea that these magnetic patterns are relics of plate tectonics on Mars is likely to be controversial, and in their paper Connerney and his colleagues consider several possible alternative explanations for their findings. For example, although it would be difficult to explain the alternating magnetic orientation of the stripes in this scenario, lava flows from volcanic eruptions can create a linear shape. When interpreting information from other planets, "we have to be careful not to stick rigidly to our terrestrial experiences," cautioned Connerney. "At least we can start the discussion here."

That the information was collected at all was the serendipitous consequence of an effort to use less rocket fuel. The Mars Global Surveyor spacecraft used a low-power technique known as aerobraking that took advantage of the drag exerted by Mars' atmosphere to slow the spacecraft down and reign in its orbit close to the planet. During the aerobraking process, the spacecraft made many passes around the planet and frequently dipped to low altitudes, allowing the magnetometer on board to take surprisingly extensive, detailed readings of the planet's surface. In addition, a problem with one of the solar panels on board forced the spacecraft to proceed with aerobraking more slowly than usual-allowing even more information to be collected.

ORDER ARTICLE #17: "Magnetic Lineations in the Ancient Crust of Mars," by J. E. P. Connerney, M. H. Acuña, and P. J. Wasilewski at NASA Goddard Space Flight Center in Greenbelt, MD; N. F. Ness at U. of Delaware in Newark, DE; H. Reme, C. Mazelle, and D. Vignes at Centre d'Etude Spatiale des Rayonnements, CNRS, in Toulouse, France; R. P. Lin and D.L. Mitchell at U. of California in Berkeley, CA; P. A. Cloutier at Rice U. in Houston, TX. CONTACT: Jack Connerney at 301-286-5884 (phone), 301-286-1683 (fax), or (e-mail); or M. H. Acuña at 301-286-3612 (phone), or (e-mail)

ORDER ARTICLE #16: "Global Distribution of Crustal Magnetization Discovered by the Mars Global Surveyor MAG/ER Experiment," by M. H. Acuña, J. E. P. Connerney, and P. Wasilewski at NASA Goddard Space Flight Center in Greenbelt, MD; N. F. Ness at U. of Delaware in Newark, DE; R. P. Lin, D. Mitchell, C. W. Carlson, J. McFadden, and K. A. Anderson at U. of California in Berkeley, CA; H. Reme, C. Mazelle, and D. Vignes at Centre d'Etude Spatiale des Rayonnements, CNRS, in Toulouse, France; P. Cloutier at Rice U. in Houston, TX. CONTACT: M. H. Acuña at 301-286-3612 (phone), or (e-mail); or Jack Connerney at 301-286-5884 (phone), 301-286-1683 (fax), or (e-mail).

For copies of this article please email, call 202-326-6440 or fax the form below to 202-789-0455. For related visuals please contact Heather Singmaster at 202-326-6414 or

NAME _______________________________________________________________
NEWS ORGANIZATION _______________________________________________________________
PHONE _______________________________________________________________
FAX _______________________________________________________________

American Association for the Advancement of Science

Related Mars Articles from Brightsurf:

Water on ancient Mars
A meteorite that originated on Mars billions of years ago reveals details of ancient impact events on the red planet.

Surprise on Mars
NASA's InSight mission provides data from the surface of Mars.

Going nuclear on the moon and Mars
It might sound like science fiction, but scientists are preparing to build colonies on the moon and, eventually, Mars.

Mars: Where mud flows like lava
An international research team including recreated martian conditions in a low-pressure chamber to observe the flow of mud.

What's Mars made of?
Earth-based experiments on iron-sulfur alloys thought to comprise the core of Mars reveal details about the planet's seismic properties for the first time.

The seismicity of Mars
Fifteen months after the successful landing of the NASA InSight mission on Mars, first scientific analyses of ETH Zurich researchers and their partners reveal that the planet is seismically active.

Journey to the center of Mars
While InSight's seismometer has been patiently waiting for the next big marsquake to illuminate its interior and define its crust-mantle-core structure, two scientists, have built a new compositional model for Mars.

Getting mac and cheese to Mars
Washington State University scientists have developed a way to triple the shelf life of ready-to-eat macaroni and cheese, a development that could have benefits for everything from space travel to military use.

Life on Mars?
Researchers from Hungary have discovered embedded organic material in a Martian meteorite found in the late 1970s.

New evidence of deep groundwater on Mars
Researchers at the USC Arid Climate and Water Research Center (AWARE) have published a study that suggests deep groundwater could still be active on Mars and could originate surface streams in some near-equatorial areas on Mars.

Read More: Mars News and Mars Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to