Researchers: Mars once hummed with magnetism, like Earth

April 29, 1999

(CNN) -- New information from the Mars Global Surveyor spacecraft suggests the barren planet once had geology like that of Earth, with a torrid interior spurting molten rock and massive plates drifting on the surface.

Plate tectonics -- which is the way big sections of a planet's surface slide around over billions of years -- was thought to be a process that only happened on Earth and that required water, a basic precondition for life. If it happened on Mars too, that would add new ammunition for those who believe life existed there at one time.

This may mean the very young Mars resembled the very young Earth, but that Mars ran out of its internal energy sources and became a geologically dead planet early in its history, said Norman F. Ness of the University of Delaware and co-author of the study.

"The data suggests that Mars was once magnetic and was far more similar to Earth's global magnetic field than had previously assumed," Ness said.

Planetary fraternal twins

Evidence of this magnetic field is frozen in rocks that were molten when the magnetic field existed. When the rocks hardened they retained the original magnetism, and that now has been detected and mapped by the spacecraft.

"At the present time there is no evidence of a global magnetic field on Mars," Ness said. "That means the dynamo died and what is left is the memory of that dynamo, stored in the crustal rocks like a magnetic tape recording."

"If it were possible to say that early Mars did in fact have plate tectonics, that would be another argument that would lead you toward expectation of life on Mars, because it would be more Earth-like," said John Connerney, one of the authors of a report on the subject in this week's edition of the journal Science.

Mars and Earth are like fraternal twins created 4.5 billion years ago, Connerney said in a telephone interview. Bigger twin Earth is still driven by its fiery heart to push its continents apart and smash them together, while Mars is cold with only magnetic indications that this once took place.

Steve Maran, assistant director of space sciences at NASA's Goddard Space Flight Center, where Connerney is based, called the report "mind-blowing."

"(Connerney's report means) The early Mars was like an early Earth and something made that all go away," Maran said by telephone. "It's gone from a live planet to a dead planet and it increases our interest in getting sample rocks back and looking for the possibility of early microbial life on Mars."

Conflicting view

Not all are convinced. In an accompanying article, paleomagnetist Ronald Merill of the University of Washington, Seattle, was quoted as saying, "If plate tectonics was operating on Mars, it worked differently or it was recorded differently by the rocks."

Connerney's research was based on data gathered by the Mars Global Surveyor, an unmanned craft launched by the National Aeronautics and Space Administration to repeatedly orbit the planet at low altitude, low enough to see patches of magnetized rock on the surface.

At first, the magnetized patches seemed random, but as the spacecraft gathered more information, a pattern of "zebra stripes" of positive and negative charges emerged -- very similar to what scientists found on the sea floor of Earth.

On Mars, the stripes seem to be more strongly magnetized and much larger, but Connerney theorized they were formed by plate tectonics, the same process that on Earth accounts for earthquakes, volcanoes and some mountain ranges.

Earth's oceans are essential to the process, lubricating the plates and helping them slip more easily. But this does not necessarily mean there were ever oceans on Mars -- though Connerney believes some water was necessary, possibly enough to support some kind of life.

'What happened to the water?'

"It would be surprising if water weren't there, in apparent river beds and large canyons," Connerney said. "The real mystery today has been, what happened to the water?"

Vicki L. Hansen, a Southern Methodist University geologist, said that the fate of Mars also awaits the Earth. She said that eventually Earth also will exhaust its internal energy and its molten core will cool. This will shut down the planet's magnetic field and allow radiation from the sun to strip away the Earth's atmosphere and water.

"What Mars went through at a very young age is what will occur on the Earth eventually," she said.

Ness said that Mars died much more quickly than Earth because the red planet is smaller and had much less internal heat generated by friction and the decay of radioactive minerals.

The Associated Press and Reuters contributed to this report.