'Deflector Shields' protect the Lunar Surface

Jul 19, 2012 By Jake Gilmore 
This image shows a truly miniature, magnetosphere recreated in the laboratory. The plasma “bubble” shown here is a mere inch across in total. The purple glow, seen in the photograph, is the stream of super-heated hot gas particles (plasma) of the Solar Wind Tunnel. You'd expect this stream to scorch the metal target. Without a magnetic field it would. But the experiment shows how instead what happens is a thin barrier or “skin” is formed of the plasma itself, within which a tiny cavity in the pseudo- solar wind is formed, which holds back the hazardous particles, so protecting the target except for at the magnetic poles. On the moon this cavity formation prevents the bombarding particles of the solar wind from weathering or darkening the surface color, keeping it white. The barrier width is about 100th the width that such a weak magnetic field (known to exist on the Moon’s surface) could possibly bend a heavy, fast moving, positively charged proton ion out of the way. So something else must be deflecting the ions into such a narrow "skin". That is an electric field the origin of which although complicated has been theoretically determined by the team and found to match the values seen in space by spacecraft and in the laboratory recreation. Credit: RAL Space & Uni. of York

(Phys.org) -- Scientists from RAL Space at the Rutherford Appleton Laboratory have solved a lunar mystery and their results might lead the way to determining if the same mechanism could be artificially manipulated to create safe havens for future space explorers.  Their work focussed on the origin of the enigmatic "lunar swirls" - swirling patches of relatively pale lunar soil, some measuring several tens of km across, which have been an unresolved mystery - until now.

In the Apollo era it was realised that lunar swirls were associated with localized magnetic fields in the lunar crust (so-called lunar 'magnetic anomalies').

Several unmanned spacecraft, like NASAs Lunar Prospector, JAXA Kaguya and India’s Chandrayaan-1 have taken a special interest in the regions of magnetic anomalies. Lunar Prospector first identified magnetic anomalies that had created fully formed but miniature “magnetospheres” similar to what the Earth’s planetary wide does on a much larger scale.

Using a combination of the space data and laboratory scale experiments using a “Solar Wind Tunnel” – the team were able to identify how such small scale magnetic “bubbles” were more efficient in deflecting the solar wind particles  bombarding the moon.

“When we first tried the experiment in the Solar Wind Tunnel and it worked, it was very exciting.” says lead scientist Dr. Ruth Bamford of the Centre for Fundamental Physics and RAL Space at the Rutherford Appleton Laboratory.

"The active force which deflect the solar wind particles is electric not magnetic. The electric field is created naturally by the edges of the moon's magnetic 'bubbles", Dr Bamford explains. "What matters is the "gradient" in the magnetic field, rather than the overall size of the magnetic bubble. So they can be as small as you like - as long as the gradient is steep enough."

Understanding how "mini-magnetospheres" produce a cavity in the solar wind and exclude the interplanetary magnetic field might lead the way to determining if the same mechanism could be artificially manipulated to create safe havens for future space explorers.

“We still need to determine quite how effective this mechanism would be at deflecting the real hazardous higher energy particles. The jury is still out on that one, but such an active shield could make the difference between survivable and certain death for astronauts on their way to Mars”.

The lunar soil was originally white but is known to have is been darkened over time by exposure to the charged particles of the "solar wind".

It has long been thought that the swirls were a result of magnetic shielding of the lunar surface from the solar wind, but nobody understood how the relatively weak magnetic fields associated with lunar swirls could sufficiently protect the moon's surface over hundreds of millions of years to prevent surface darkening and produce such finely detailed patterns.

According to Dr. Bamford, "Close to the moon's surface, the strength of a magnetic anomaly is likely to be very irregular, featuring overlapping "cavities" and "gradients".  We cannot know the precise arrangement without going there to see for ourselves", but the result on the surface would be a corresponding pattern of retarded and accelerated "space weathering", visible as areas of lighter material separated by darks "lanes".  Over an estimated 3.8 billion years these anomalies would have been deflecting the solar wind particles streaming in from space, slowly creating these amazing patterns, which can be clearly seen on the lunar surface today.

The idea was confirmed by experiments done in the laboratory with the University of York in the U.K. using their "Plasma Wind Tunnel".  The particles generated were indeed "corralled" by a narrow electrostatic field, so protecting areas of the exposed surface.

The interaction of the with the field anomalies have been shown, to be effective enough to create protected voids above the surface of the , sufficient to stave off against weathering caused by the bombardment of solar particles.

Details are to be published in the scientific journal Physical Review Letters and at Physics Arxive: arxiv.org/abs/1207.2076

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tadchem
4 / 5 (1) Jul 19, 2012
Just how strong is the magnetic field of the moon, in comparison to that of the earth?
Is there data from the Apollo missions that supports this hypothesis?
Can lunar auroras be detected at its magnetic poles?
El_Nose
3.3 / 5 (4) Jul 19, 2012
@tadchem

The moon has no magnetosphere. The isssue is that satellites observed a few years ago that solar wind particles were being reflected by something on the moon. Not the entire moon just localised areas -- 'miniature magnetospheres' -- this is an attempt to prove that localized fields might be strong enough to repel solarwind particles.

What was odd in the satellite observations as a note was that lower energy particles below 100 eV were not repeled.

As a whole there is no evidence of a magnetosphere on our silvery neighbor - but small areas that seem to isolate themselves.

IMO - probably just strongly magnetic meteorite fragments.

-- but its cool to think that the star trek deflector shield is being born. Sad that it is simply a magnetic field
Sean_W
3 / 5 (6) Jul 19, 2012
@tadchem

If there had been a magnetic field for the moon it still would have been hard if not impossible to detect an aurora since they are formed when such a field channels solar wind particles into an *atmosphere*. What little atmosphere which exists on the moon is spread too thin to be seen if it was energized. I think I have heard it said that if you took all of the moon's atmosphere and compressed it down to the pressure of Earth's it would only fill a stadium sized volume. Since the lunar surface is comparable to the area of the African continent, that stadium worth of air is virtually negligible. Good question though.
Ventilator
not rated yet Jul 19, 2012
So, for the sake of the future research to come from this, one puts large numbers of emitter arrays for multiple electromagnetic shields across a ship, rather than one main emitter?

Interesting, this is somewhat counter-intuitive to me, however, it does stand up under critical thinking, as the shape of the shield layer seems to be more important than its intensity.
Torbjorn_Larsson_OM
5 / 5 (2) Jul 19, 2012
@ tadchem:

"Just how strong is the magnetic field of the moon, in comparison to that of the earth?"

That is unknown AFAIK. We now know that the Moon has an active core, by better signal analysis of Apollo seismic data, and it could well have a dynamo field still. It would be relatively weak and hard to distinguish from the interplanetary magnetic field (~ 10 nT).

A more shortlived dynamo was suggested 2009 by Takahashi et al ["Thermal core-mantle coupling in an early lunar dynamo: Implications for a global magnetic field and magnetosphere of the early Moon", Geophys Res Ltrs] Such a field could still be ~ 100 nT field strength; Earth has ~ 25 000 - 65 000 nT.

A Moon mag field could even have affected the early Earth atmosphere (early hydrodynamical hydrogen escape), so it is important to find out. Even more so if the dynamo is still active.
Torbjorn_Larsson_OM
5 / 5 (1) Jul 19, 2012
[cont] (The early Moon was much closer.)

The initial field could have been ~ 1 000 -100 000 nT seen in Apollo grains, comparable with Earth as it is now. (Though I believe the magnetic grains have had other explanations since.)

A frozen in diapir (first upwelling from the mantle, that on Earth started convection and so plate tectonics) could predict the Moon surface magnetic anomalies, many such have been observed.
Torbjorn_Larsson_OM
5 / 5 (3) Jul 19, 2012
Aah, my mistake, I forgot to check with the new orbiters' results. El Nose is correct:

"The Moon has an external magnetic field of the order of one to a hundred nanoteslas, less than one-hundredth that of the Earth. It does not currently have a global dipolar magnetic field, as would be generated by a liquid metal core geodynamo, and only has crustal magnetization, probably acquired early in lunar history when a geodynamo was still operating.[73][74] Alternatively, some of the remnant magnetization may be from transient magnetic fields generated during large impact events, through the expansion of an impact-generated plasma cloud in the presence of an ambient magnetic fieldthis is supported by the apparent location of the largest crustal magnetizations near the antipodes of the giant impact basins.[75]" [Wp]

So the remnant field is compatible with Takahashi, while the magnetic grains and surface magnetic anomalies have now an alternate explanation in early large impacts.
lbuz
4.3 / 5 (6) Jul 19, 2012
Kudos to all the commentators above. It is so refreshing to see good questions addressed in a collegial and self correcting fashion, sans diatribes, ax grinding and dead horse beating! An excellent example of what the Phys.org site COULD be.
Skepticus
2 / 5 (4) Jul 19, 2012
So,..one puts large numbers of emitter arrays ..across a ship, rather than one main emitter?..

Your thoughts parallel mine! An array of emitters would probably overcomes the leakage problem at the magnetic poles of the emitters. By switching emitters on an off rapidly in staged sequences (he he, "shield frequency" ala Star Trek-here it comes!), the combined magnetic fields should overlap and/or rotating, thus shifting and blurring the weak spots of the poles. Also, by pulsing the emitters, time-variant magnetic fields are naturally produced. A changing mag field creates an electric field, of which is quite convenient, as Dr Bamford explains: "The active force which deflect the solar wind particles is electric not magnetic.... "
Skepticus
2 / 5 (4) Jul 20, 2012
I can imagine a rough first-order doable, inexpensive experiment of this "pulsed emitter array" concept. An array of solenoids energized and controlled by appropriately built transistors circuit for sequential/staged/overlapping firing, exposed to the stream of plasma from a plasma torch, or in a pinch, a capable plasma-creating source such as the HV corona discharge from a heavy duty fly-back transformer, or from the HV output of a microwave oven's transformer. It would be so much fun...
Picard
5 / 5 (4) Jul 20, 2012
I can imagine a rough first-order doable, inexpensive experiment of this "pulsed emitter array" concept. An array of solenoids energized and controlled by appropriately built transistors circuit for sequential/staged/overlapping firing, exposed to the stream of plasma from a plasma torch, or in a pinch, a capable plasma-creating source such as the HV corona discharge from a heavy duty fly-back transformer, or from the HV output of a microwave oven's transformer. It would be so much fun...


Make it so.
elektron
1 / 5 (1) Jul 20, 2012
I was under the impression that the current moon formation theory, ie being a lump of molten earth mantle thrown into orbit after a collision, meant that there was no iron core. I also believed that the density of the moon is also consistent with there being no iron core. Is this correct, if so what could be the cause of any appreciable magnetic influence from the Moon that would shield it?
mortoo
5 / 5 (2) Jul 20, 2012
Google suggests that the lunar magnetic anomalies come from impacts - presumably from iron containing bodies.

But I suggest waiting until we have a spaceship headed for Jupiter before we start digging up any magnetic anomalies on the moon.
AWaB
not rated yet Jul 20, 2012
It's time for the stars!
SteveL
not rated yet Jul 22, 2012
Time for moons and planets, the stars can wait until we can get there. As for the moons and planets; the only thing stopping us is us.
Kimben
not rated yet Jul 23, 2012
I think most of you guys are missing the point. " Deflector Shields", with more reserch i believe this is the future of far space travel. Shields from deadly radiation.