Star Trek for Real: Impenetrable Force Field Protects Earth
Radiation belts discovered at the dawn of the space age have a new trick in their pocket: shielding the Earth.
On January 30, 1958, the U.S. launched its first orbiting satellite, Explorer 1. On board was a geiger counter instrument developed by James Van Allen and his team from the University of Iowa. The counter went “off the charts” at a certain altitude, measuring an unexpected level of radiation. Further flights isolated this high energy radiation to two belts above the Earth, named the Van Allen Radiation Belts in his honor. It was the first major scientific discovery of the space race, after the Russians had successfully launched two Sputnik probes and the dog Laika in late 1957.
Now, 56 years after their discovery, physicists have discovered that the Van Allen belts have a new function: protecting Earth. Nature reported it this week. Between the inner and outer belts is an “impenetrable” barrier that shields the Earth from the solar wind’s highest-energy electrons:
Early observations indicated that the Earth’s Van Allen radiation belts could be separated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. Subsequent studies showed that electrons of moderate energy (less than about one megaelectronvolt) often populate both zones, with a deep ‘slot’ region largely devoid of particles between them. There is a region of dense cold plasma around the Earth known as the plasmasphere, the outer boundary of which is called the plasmapause. The two-belt radiation structure was explained as arising from strong electron interactions with plasmaspheric hiss just inside the plasmapause boundary, with the inner edge of the outer radiation zone corresponding to the minimum plasmapause location. Recent observations have revealed unexpected radiation belt morphology, especially at ultrarelativistic kinetic energies (more than five megaelectronvolts). Here we analyse an extended data set that reveals an exceedingly sharp inner boundary for the ultrarelativistic electrons. Additional, concurrently measured data reveal that this barrier to inward electron radial transport does not arise because of a physical boundary within the Earth’s intrinsic magnetic field, and that inward radial diffusion is unlikely to be inhibited by scattering by electromagnetic transmitter wave fields. Rather, we suggest that exceptionally slow natural inward radial diffusion combined with weak, but persistent, wave–particle pitch angle scattering deep inside the Earth’s plasmasphere can combine to create an almost impenetrable barrier through which the most energetic Van Allen belt electrons cannot migrate.
In other words, this invisible shield protects the planet from deadly particles. Astrobiology Magazine calls them “killer electrons.” A press release from the University of Colorado, Boulder, says these electrons “whip around the planet at near-light speed and have been known to threaten astronauts, fry satellites and degrade space systems during intense solar storms.” The press release calls it a “Star Trek-like invisible shield.” The articles did not mention what the long-term impact of exposure to “killer electrons” might be, but anything that could fry a satellite is bound to be life-limiting for the biosphere.
About the same time, scientists at the University of Zurich reported that DNA on the outside of a rocket had survived re-entry into the Earth’s atmosphere. “Completely surprised” by the durability of the DNA, which remained able to pass on genetic information after landing, the scientists think it might impact thoughts about extraterrestrial life. It’s not clear from the press release, however, if the rocket reached a high enough altitude to pass through the layer of killer electrons. A different result might obtain from exposure outside the shield and farther out beyond Earth’s magnetosphere.
How does the shield form? The scientists are not exactly sure. It’s uncanny, almost like a conspiracy:
The latest mystery revolves around an “extremely sharp” boundary at the inner edge of the outer belt at roughly 7,200 miles in altitude that appears to block the ultrafast electrons from breeching the shield and moving deeper towards Earth’s atmosphere.
“It’s almost like theses electrons are running into a glass wall in space,” said Baker, the study’s lead author. “Somewhat like the shields created by force fields on Star Trek that were used to repel alien weapons, we are seeing an invisible shield blocking these electrons. It’s an extremely puzzling phenomenon.”
Dr. Baker received his PhD under James Van Allen. Another space pioneer, Dr. Henry Richter, who in 1958 had helped Van Allen’s assistant George Ludwig outfit the instrument for Explorer 1 (see 1/31/08), was delighted with the new discovery; he called it a “critical characteristic” for the Earth (personal communication). Richter, the only surviving manager of Explorer 1, oversaw the instrument payload for the satellite and provided the initial radio communication systems in California that confirmed it had reached orbit after its launch in Florida.
The discovery of this protective shield will stimulate further research, Baker says:
“Nature abhors strong gradients and generally finds ways to smooth them out, so we would expect some of the relativistic electrons to move inward and some outward,” said Baker. “It’s not obvious how the slow, gradual processes that should be involved in motion of these particles can conspire to create such a sharp, persistent boundary at this location in space.” …
“It’s like looking at the phenomenon with new eyes, with a new set of instrumentation, which give us the detail to say, ‘Yes, there is this hard, fast boundary,’” said John Foster, associate director of MIT’s Haystack Observatory and a study co-author.
Data were collected by twin Van Allen Probes in 2012, but the analysis was just reported this week. “The inner edge of the relativistic electron population is a remarkable feature at all geographic longitudes,” the Nature paper concludes. “It has not previously been discussed in the literature because we have never previously had such accurate measurements at high energies.” New Scientist, Science Daily, Frontline Desk and other science media sites relayed the discovery, enjoying especially the reference to Star Trek.
This is an exciting find that challenges astrobiology and supports intelligent design. It appears to point out another requirement for habitability: not just the right distance from a star (and a dozen other factors—8/15/14), but a magnetic field the right size and structure to shield a planet’s biosphere from deadly radiation. Mars, despite a patchy magnetic field, receives radiation that fries organic compounds (9/05/14). Since the newly-discovered shield cannot be accounted for as a natural property of the Earth’s magnetospheric structure, it may point to a “conspiracy” (following on Baker’s term) of several processes working together. If so, that makes it even more improbable that an exoplanet would have just the right plasmasphere and magnetosphere to create such an effective shield.
A word on Dr. Henry Richter: I met him at JPL in 2007 when he had come to research the history of Explorer 1. He appeared in a documentary produced by the lab for the 50th anniversary celebrations on January 30, 2008, at which he was a V.I.P. Unrelated to the earthquake specialist, Charles Richter, Dr. Henry Richter received a chemistry PhD from Caltech and was a professor there till he was invited to work at the fledgling Jet Propulsion Laboratory. After Explorer 1’s historic success (that resulted in the creation of NASA), he also worked on the on the Ranger and Surveyor missions to the moon that preceded the Apollo program. He was the lead man planning and locating the sites for the Deep Space Network, still in operation in California, Spain and Australia. Dr. Richter received honors with JPL’s surviving directors in Washington DC at ceremonies in 2008 and was honored at the Deep Space Network’s 50th anniversary earlier this year (April 2, 2014).
Years after leaving the lab in the early 1960s, Dr. Richter became a Christian and a creationist. When he came back to the lab as a retiree, he looked me up because of that shared interest (he had read some of my articles for ICR). We became good friends and met anytime he visited the lab. At a lecture on Explorer 1 at the lab in 2008, he ended by sharing his personal testimony. During my ordeal over being disciplined and demoted for having shared intelligent design DVDs in 2009, he personally intervened with JPL’s deputy director, unfortunately, to no avail (he said that kind of thing would never have happened when he was on staff). Dr. Richter is a gentleman and humble Christian with an incredible life story. I am honored to be able to call this great American a personal friend. We are currently collaborating on a book he conceived on intelligent design.