U.S. spacecraft detects magnetic field of Mars Data will feed debate on whether planet ever supported life

September 18, 1997|By NEWSDAY

WASHINGTON -- An U.S. spacecraft that went into orbit around Mars last week has found the first conclusive evidence the red planet has a magnetic field, the National Aeronautics and Space Administration said yesterday.

The Mars Global Surveyor detected the magnetic field Monday as its instruments began gathering data. The field is no more than 1/800th as strong as Earth's.

But scientists said even that is stronger than expected and suggests that Mars might once have had a more robust field, perhaps generated by the same sort of internal geologic mechanisms as Earth's.

A better understanding of the Martian magnetic field should give clues to the early history of the planet and why it evolved so differently from Earth, they said. It also could shed light on whether conditions once were more conducive to primitive life on Mars.

"This is a nice, exciting result," said Mario Acuna of NASA's Goddard Space Flight Center in Greenbelt.

Acuna said previous studies by Russian spacecraft had been inconclusive regarding the presence or absence of a global magnetic field. The possibility had been debated by researchers for years.

The new finding, while preliminary, seems solid, Acuna said. "We had no dissent on our team," he said.

"I think it's very interesting," agreed Margaret Kivelson, a University of California, Los Angeles specialist on magnetic fields who is not associated with the Global Surveyor team. "It certainly will be revealing," she said, as the spacecraft gathers more data on the strength and geometry of the Martian magnetic field.

During the next four months, Global Surveyor will settle into a tighter, more circular orbit around Mars in preparation for a two-year mission to photograph and map the planet's surface.

A planet generates a magnetic field when its rotation causes an electrically conductive material -- such as the molten iron in Earth's core -- to spin. That movement causes electric currents to flow deep within the planet. Those currents, in turn, give rise to magnetic field lines that can encircle the planet. Such a mechanism -- called a dynamo -- is believed to be the source of the magnetic fields of Earth, Jupiter, Saturn, Uranus and Neptune.

Acuna and others said the source of the newly confirmed Martian magnetic field is not yet known. It could be the remnants of a dying but still weakly active dynamo at the heart of Mars. Or, they said, the molten core might have solidified and the field could be due to magnetism still remaining in the martian crust from the activity of a now-extinct dynamo.

The finding of a global magnetic field at Mars supports the view that the planet once have had sufficient internal heat to give rise to volcanoes and other geologic activity on the surface. It also has implications for the lively debate on whether Mars once had an environment more favorable for life.

"A magnetic field shields a planet from fast-moving, electrically charged particles from the sun, which may affect its atmosphere, as well as from cosmic rays, which are an impediment to life," Acuna said. "If Mars had a more active dynamo in its past, as we suspect from the ancient volcanoes there, then it may have had a thicker atmosphere and liquid water on its surface."

Such an environment would have been more conducive to the growth of microbes than the frigid, dusty planet that exists today, scientists say.

Pub Date: 9/18/97

Baltimore Sun Articles
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.