Researchers at Rensselaer Polytechnic Institute propose a new theory, based on a richer, more accurate image of magnetic fields and solar winds in the early solar system, and a mechanism known as multi-fluid magneto-hydrodynamics – to explain the ancient heating of the asteroid belt.

Although today the asteroid belt between Mars and Jupiter is cold and dry, scientists have long known that warm, wet conditions, suitable to formation of some life-seeding biomolecules, prevailed.

Traces of bio-molecules found inside meteorites – which originated in the asteroid belt - could only have formed in the presence of warmth and moisture.

One theory of the origin of life proposes that some of the biomolecules that formed on asteroids may have reached the surfaces of planets, and contributed to the origin of life.

"The early Sun was actually dimmer than the Sun today, so in terms of sunlight, the asteroid belt would have been even colder than it is now. And yet we know that some asteroids were heated to the temperature of liquid water, the 'goldilocks zone,' which enabled some of these interesting biomolecules to form," said researcher Wayne Roberge.

Roberge and co-author Ray Menzel revisit and refute one of two theories proposed decades ago to explain how asteroids could have been heated in the early solar system.

Both of the established theories, one involving the same radioactive process that heats the interior of Earth, and the other involving the interaction of plasma (super-heated gases that behave somewhat like fluids) and a magnetic field.

Roberge and Menzel reviewed the second theory, based on an early assessment of the young Sun and the premise that an object moving through a magnetic field will experience an electric field, which will in turn push electrical currents through the asteroid, heating the asteroid in the same way that electrical currents heat the wires in a toaster.
"They assumed some things about what the young Sun was doing which are just not believed to be true today. For example, the young sun would have had to produce a powerful solar wind which blew past the asteroids, and that's just no longer believed to be true," said Roberge.

The solar wind, and the plasma stream it produced, was not as powerful as early theorists assumed, and the researchers have corrected those calculations based on the current understanding of the young Sun, researchers said.

Roberge said that the early theorists also incorrectly calculated the position of the electric field asteroids would have experienced.
Roberge said that, in reality, an electric field would have permeated the asteroid and the space around it, a mistake very few researchers would have realized.

The study was published in The Astrophysical Journal.


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