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Tuesday, March 22, 2011

How Vital Is a Planet's Magnetic Field? New Debate Rises

How Vital Is a Planet's Magnetic Field? New Debate Rises

Michael Schirber, Astrobiology Magazine Contributor

Solar wind particles generate the aurora phenomena in the Earth’s atmosphere.

Our nearest planetary neighbors, Mars and Venus, have no oceans or lakes or rivers. Some researchers have speculated that they were blown dry by the solar wind, and that our Earth escaped this fate because its strong magnetic field deflects the wind. However, a debate has arisen over whether a magnetic field is any kind of shield at all.

The controversy stems from recent observations that show Mars and Venus are losing oxygen ions from their atmospheres into space at about the same rate as Earth. This came as something of a surprise, since only Earth has a strong dipolar magnetic fieldthat can prevent solar wind particles from slamming into the upper atmosphere and directly stripping away ions.

"My opinion is that the magnetic shield hypothesis is unproven," said Robert Strangeway from UCLA. "There's nothing in the contemporary data to warrant invoking magnetic fields."Each of the three planets is losing roughly a ton of atmosphere to space every hour. Some of this lost material was originally in the form of water, so this begs the question:  How did the planets end up with vastly different quantities of water if they are all "leaking" to space at similar rates?

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