A new look at the early solar system introduces an alternative to a long-taught, but largely discredited, theory that seeks to explain how biomolecules were once able to form inside of asteroids. In place of the outdated theory, researchers at Rensselaer propose a new theory—based on a richer, more accurate image of magnetic fields and solar winds in the early solar system, and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.
The Rensselaer researchers’ paper revisits and refutes one of two theories proposed decades ago to explain how asteroids could have been heated in the early solar system. Photo Credit: NASA/JPL-Caltech
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 biomolecules, the building blocks of life, once prevailed. Traces of biomolecules 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 as we know it.
“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 Wayne Roberge, a professor of physics and member of the New York Center for Astrobiology, who co-authored a paper on the subject with Ray Menzel, a graduate student in physics.
What emerges is a new possibility, based on the corrected understanding of the electric fields the asteroids would have experienced, the solar wind and plasma conditions that would have prevailed, and a mechanism known as multi-fluid magneto-hydrodynamics.
—Wayne Roberge and Ray Menzel
In the paper, Menzel and Roberge 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—are still taught to students of astrobiology. Although radioactive heating of asteroids was undoubtedly important, current models of radioactive heating make some predictions about temperatures in the asteroid belt that are inconsistent with observations.
Motivated by this, Roberge and Menzel reviewed the second of the two theories, which is 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. According to this theory, as an asteroid moves through the magnetic field of the solar system, it 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.
“It’s a very clever idea, and the mechanism is viable, but the problem is that they made a subtle error in how it should be applied, and that’s what we correct in this paper,” said Roberge. “In our work, we correct the physics, and also apply it to a more modern understanding of the young solar system.”
“We’re just at the beginning of this. It would be wrong to assert that we’ve solved this problem. What we’ve done is to introduce a new idea. But through observations and theoretical work, we now have a pretty good paradigm.
Menzel said the researchers have now definitively refuted the established theory.
What emerges, Menzel and Roberge said, is a new possibility, based on the corrected understanding of the electric fields the asteroids would have experienced, the solar wind and plasma conditions that would have prevailed, and a mechanism known as multi-fluid magneto-hydrodynamics.
Magneto-hydrodynamics is the study of how charged fluids—including plasmas—interact with magnetic fields. The magnetic fields can influence the motion of the charged fluid, or plasma, and vice versa.
Menzel and Roberge said their new theory is promising, but it raises many questions that merit further exploration.
“We’re just at the beginning of this. It would be wrong to assert that we’ve solved this problem,” Roberge said. “What we’ve done is to introduce a new idea. But through observations and theoretical work, we now have a pretty good paradigm.”