NASA Van Allen Probes: Mysteries of Earth's radiation belts uncovered

The twin Van Allen Probes were launched on August 30, 2012 into elliptical, near-equatorial orbits around the Earth. 

Remarkably, rather than seeing just the well-known two-belt structure, the mission found almost immediate evidence of the clear three-belt structure portrayed in green in this diagram. 

Image courtesy of Andy Kale, University of Alberta.

Just over a year since launch, NASA's Van Allen Probes mission continues to unravel longstanding mysteries of Earth's high-energy radiation belts that encircle our planet and pose hazards to orbiting satellites and astronauts.

Derived from measurements taken by a University of New Hampshire-led instrument on board the twin spacecraft, the latest discovery reveals that the high-energy particles populating the radiation belts can be accelerated to nearly the speed of light in conjunction with ultra-low frequency electromagnetic waves operating on a planetary scale.

This mode of action, as detailed in a paper recently published in the journal Nature Communications, is analogous to that of a cyclical particle accelerator like the Large Hadron Collider (LHC).

However, in this case, the Earth's vast magnetic field, or magnetosphere, which contains the Van Allen belts, revs up drifting electrons to ever-higher speeds as they circle the planet from west to east.

The recent finding comes on the heels of a related discovery—also made by the UNH-led Energetic Particle, Composition, and Thermal Plasma (ECT) instrument suite—showing similar particle acceleration but on a microscopic rather than a planetary scale.

Harlan Spence

"The acceleration we first reported operates on the scale size of an electron's gyromotion—it is a really local process, maybe only a few hundred meters in size," notes Harlan Spence, director of the UNH Institute for the Study of Earth, Oceans, and Space, principal scientist for the ECT, and coauthor on the Nature Communications paper.

"Now we're seeing this large-scale, global motion involving ultra low-frequency waves pulsing through Earth's magnetosphere and operating across vast distances up to hundreds of thousands of kilometers."

And, Spence adds, "in all likelihood both processes are occurring simultaneously to accelerate particles to relativistic speeds."

Understanding the complex dynamics of the particle acceleration will help scientists make better predictions of space weather conditions and, thus, offer better protections to orbiting satellites crucial to modern-day society.

Having twin spacecraft making simultaneous measurements in different regions of nearby space is a key part of the mission as it allows the scientists to look at data separated in both space and time.

"With the Van Allen Probes, I like to think there's no place for these particles to hide because each spacecraft is spinning and 'glimpses' the entire sky with its detector 'eyes', so we're essentially getting a 360-degree view in terms of direction, position, energy, and time," Spence says.

NASA Orion Crew Spacecraft (MPCV) Uncovered

Credit: Jim Grossmann/NASA

At NASA’s Kennedy Space Center in Florida, Lockheed Martin crew members uncover the Orion ground test vehicle in the Launch Equipment Test Facility (LETF). 

After a move from the Operations and Checkout Facility to the LETF, the ground test vehicle will undergo a series of pyrotechnic bolt tests. 

Launching atop NASA's heavy-lift Space Launch System, also under development, the Orion Multi-Purpose Crew Vehicle MPCV will carry astronauts beyond low Earth orbit and back. 

It will also provide emergency abort capabilities. Image released May 13, 2013.

Mechanism uncovered behind Salmonella virulence and drug susceptibility

Researchers have discovered a novel mechanism in Salmonella that affects its virulence and its susceptibility to antibiotics by changing its production of proteins in a previously unheard of manner. This allows Salmonella to selectively change its levels of certain proteins to respond to inhospitable conditions.

Although the mechanism had not been recognized before, the scientists were intrigued to find evidence of a similar mechanism in all five kingdoms of life — animals, plants, fungi, protista, and monera.

The findings were published today, July 29, in Molecular Cell. The senior author of the study is Dr. Ferric C. Fang, professor of microbiology, laboratory medicine, and medicine at the University of Washington (UW). Fang also directs the Clinical Microbiology Laboratory at Harborview Medical Center in Seattle. The lead author is William Wiley Navarre, who began the study as a postdoctoral fellow in the Fang lab and is now an assistant professor at the University of Toronto.

Salmonella enters the gut when people eat contaminated food, and can sometimes spread to other parts of the body. Illness outbreaks and grocery recalls related to Salmonella are often in the news. Babies, young children, the elderly, and people with cancer or HIV are especially prone to severe illness from Salmonella.

Salmonella is adaptable and can withstand many of the body’s attempts to fight it. The bacteria live and multiply in a special compartment inside the cells of an infected person or animal. Salmonella can alter its physiology as it moves from a free-swimming life to its residence in a host cell. Salmonella’s metabolism also changes over time to make use of the nutrients available in the host cell, and to survive damage from the build-up of oxidants and nitric oxide in the infected cell.

While screening mutant Salmonella that were resistant to a form of nitric oxide that normally stops the bacteria from dividing, Navarre, Fang and their research collaborators found mutations in two little-known genes. These are the closely linked poxA and yjeK genes. In a number of bacteria, these two genes are associated with a third gene that encodes the Bacterial Elongation Factor P, which is involved in protein production.

The researchers discovered that these three genes operate in a common pathway that is critical for the ability of the Salmonella bacteria to cause disease and resist several classes of antibiotics. Salmonella with mutations in either the poxA gene or the yjeK genes, the study noted, appear to be nearly identical and show similar changes in proteins involved in metabolism. Strains with mutations in both genes resemble the single mutant strains, an observation that suggests the two genes work in the same pathway.

The mutant strains exhibited many abnormalities under stressful conditions.