Researchers propose new theory to explain seeds of life in asteroids

Oct 01, 2013
Credit: NASA/JPL-Caltech

( —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 In place of the outdated theory, researchers at Rensselaer Polytechnic Institute propose a new theory – based on a richer, more accurate image of magnetic fields and solar winds in the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 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 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 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 within the School of Science at Rensselaer, 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. "Here's the question: How could that have happened? How could that environment have existed inside an asteroid?"

In the paper, titled "Reexamination of Induction Heating of Primitive Bodies in Protoplanetary Disks" and published today in the Astrophysical Journal, 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 – 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 . 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."

Menzel said the researchers have now definitively refuted the established theory.

"The mechanism requires some extreme assumptions about the young solar system," Menzel said. "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."

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. Roberge said 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.

"We've calculated the electric field everywhere, including the interior of the asteroid," Roberge said. "How that electric field comes about is a very specialized thing; about 10 people in the world study that kind of physics. Fortunately, two of them are here at RPI working together."

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 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. Magneto-hydrodynamics had a moment of fame as the propulsion system for an experimental nuclear submarine in the 1990 movie The Hunt for Red October.

Multi-fluid magneto-hydrodynamics are an even more specialized variation of the mechanism that apply in situations where the plasma is very weakly ionized, and the neutral particles behave distinctly from the charged particles.

"The neutral particles interact with the charged particles by friction," Menzel said. "So this creates a complex problem of treating the dynamics of the neutral gas and allowing for the presence of the small number of charged particles interacting with the magnetic field."

Menzel and Roberge said their new 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 know have a pretty good paradigm."

And much as Menzel and Roberge benefited from recent progress in understanding the physical conditions in an emerging planetary system, they hope their own work will advance the field of astrophysics.

"There are a lot of byproducts of this work because, in the course of doing this, we had to really zero in on how an interacts with the of the young ," said Roberge. "There are a lot of physical processes that we had to consider that have not been considered in this context before."

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User comments : 10

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1 / 5 (12) Oct 01, 2013
"How that electric field comes about is a very specialized thing; about 10 people in the world study that kind of physics."

Is it any wonder why there is so much confusion about the behavior of plasma in the Electric Universe.

Menzel said the researchers have now definitively refuted the established theory.

1 / 5 (5) Oct 01, 2013
The prefix 'bio-' in front of 'molecules' is the prerequisite and definition for life.
Akin to saying a life form without a brain is the prerequisite for life and yet not a definition for life.
This makes the physics of life a slave to a definition or at least to the prefix 'bio'.
1 / 5 (9) Oct 01, 2013
An even more viable theory is that the traces of life originated on planets, as did the asteroids. Violently explosive events excavated the material from planetary surfaces, biological matter along for the ride.
4.6 / 5 (10) Oct 01, 2013
OMG, the level of ignorance in these posts is staggering. Thanks for reminding me why I spend my time in the lab actually doing science rather than wasting my time on this forum. Go spend a lifetime actually learning something, you'll be amazed by what you don't know.
5 / 5 (3) Oct 02, 2013
It's true that liquid water reactions produces the organic compounds what people see in asteroids. However, there is a surplus of heating mechanisms from chemical sorting, gravitational sorting, collisional heating, radioactivity, irradtaion and yes, likely a contribution from the magnetodissipation that drives disk formation in the first place.

But these researchers erroneously paints their advances as a needed save in order to push the importance of what they do. We don't know that because we don't know enough of the whole system as of yet.
3.7 / 5 (3) Oct 02, 2013
pauljpeace, it is the expected antiscientist trolling from 'alternatives' and known non-alternatives (religious creationist crackpots with their magic actions).

Yes, sometimes it is genuine instead of chosen ignorance, but don't underestimate the capacity to either stupidity or insanity of people.

The train has gone on both these groups, since fusion was shown to drive the sun a century ago and evolution was shown to clade us as a branch of geochemistry a year ago (Lane & Martin).

[That doesn't mean asteroid delivery of organics is uninteresting for early geochemistry evolution. It just means it wasn't the main pathway.]
4 / 5 (4) Oct 02, 2013
"about 10 people in the world study that kind of physics"

Well, then there's our cohort of cranks here in the comment compartment. They've known it all, for quite a while, and they're practically wetting themselves in their eagerness to tell the rest of us.
1 / 5 (3) Oct 02, 2013
The protoplanetary disks were formed from the condensate of a stellar nova explosion. It was probably very warm when that happened, and has been cooling evver since.
5 / 5 (1) Oct 02, 2013
Yeah, I'm with Torbjorn. This is really a moot issue.

I think the reason nobody bothered to update the old theory was because it was dead on arrival anyway. The story above really just ammounts to some grad students applying new plasma models to the old, dead theory of asteroidal panspermia. The effort to understand plasma physics in a proplanetary system is worth doing, and our asteroids and comets might hold evidence regarding what that system was like. However, panspermia is a whole different ball of wax, and kinda pollutes the useful portion of the work here.
not rated yet Oct 07, 2013
The seeding of life theory seems shaky. The heat generated by entry into the atmosphere, followed by impact heat. Well, wouldn't most material be destroyed? I poise this as a question.