For things we can’t see, we go to PAMELA (or Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics), a module attached to a Russian satellite launched in 2006. Among a host of other duties, PAMELA’s job is to detect ever-elusive antimatter particles, which, theoretically, should be orbiting the Earth in rings.
The Earth is kind of like a giant magnet; the magnetic field creates a series of somewhat flattened concentric circles around the Earth, connected at the poles. Some of you may be familiar with the shape. It’s the same one that’s created in those ever so riveting iron-filings-on-paper experiments in grade school.
The two rings, dubbed “Van Allen radiation belts,” trap particles. “Particles can escape the outer belt in about a week, but the inner belt can hold onto particles for about a year,” writes NewScientist.com. These belts are “generally comprised of protons, electrons and helium nuclei” that are created when cosmic rays collide with nuclei already orbiting Earth, writes physorg.com.
However, due to the symmetry present in nature and results generated in the lab, scientists theorized that there should also be radiation belts comprising antimatter. Antimatter is the logical extension of the “anti-particle” to matter. An anti-particle is the mirror opposite of a given particle, the classic example being the positron (with positive charge) being the electron’s anti-particle.
Since the Earth is being bombarded with cosmic rays and particles are being created and subsequently trapped in the Van Allen belts, scientists have theorized that there should be two belts comprising antimatter. “Many of these antiparticles must be annihilated when they meet particles of ordinary matter. But some astronomers always suspected that the remaining antiprotons must become trapped by the Earth’s magnetic field, forming an antiproton radiation belt.”
PAMELA passed daily through the South Atlantic Anomaly, “a region where the Van Allen radiation belts come closest to the Earth’s surface,” writes TechnologyReview.com. This area is where the PAMELA module was theorized to be able to find antiprotons.
It turns out that once the team analyzed the data, the experiment paid off. “The PAMELA team has analysed the 850 days of data, looking only at the times when the spacecraft was in the South Atlantic Anomaly, which was about 1.7 per cent of this time.
Lo and behold, these guys found 28 antiprotons. That’s about three orders of magnitude more than you’d expect to find in the solar wind, proving that the particles really are trapped and stored in this belt,” reports TechnologyReview.com. What the findings mean is another issue entirely. At their core, the data prove that we can successfully deduce the composition of the universe around us in the lab. More importantly, they give us insight into the elusive nature of dark matter, proving that our ideas are at least partially correct. However, some researchers have loftier expectations for the results.
Alessandro Bruno, a team member from Bari, Italy, says antimatter in the Earth’s radiation belts might one day be useful for fuelling spacecraft. Bruno envisions a future where we explore the galaxy powered by the reaction between matter and antimatter. He claims the process could generate energy more efficiently than even the fusion that takes place in the Sun.
Whatever the case, PAMELA is a testament to space exploration and a sobering reminder that we’re always pushing the boundary on the final frontier, even if the shuttle isn’t there to help us.