Scientists document limited oxygen loss

Contact: Nancy Ambrosiano, nwa@lanl.gov, (505) 665-4610 (01-028)

Recent News Los Alamos scientist named Asian American Engineer of the Year Los Alamos scientist featured in NASA science update Los Alamos muon detector could thwart nuclear smugglers Wojciech H. Zurek named Phi Beta Kappa visiting scholar Four Los Alamos physicists honored by American Physical Society Los Alamos National Laboratory organizations earn seven out of 13 NNSA Pollution Prevention awards Carter Hydrick returns to the Bradbury Science Museum Feb. 15 Laboratory supports summer science program New NASA IBEX mission to carry Los Alamos instrument Beason takes top threat reduction post at Los Alamos

LOS ALAMOS, N.M., March 9, 2001 -- "The sky is falling. The sky is falling."

Okay, maybe not the sky, but scientists have found that 90 percent of the oxygen ions that escaped Earth's ionosphere and were thought to be lost to space forever are continually "falling" back to replenish our atmosphere.

That's good news, because it means that rather than losing 18 percent of Earth's atmospheric oxygen over the past three billion years Earth has only lost about two percent.

The research appeared in today's Science magazine March 9. The authors are from the Department of Energy's Los Alamos National Laboratory and three Japanese institutions. The study examines oxygen ion loss rates along four escape routes using measurements by high-altitude spacecraft.

Data show that the total oxygen ion loss rate at high-altitude is about a magnitude smaller than the loss rate observed by low-altitude spacecraft. This suggests that there may be a significant return flux from the magnetosphere to the low-latitude ionosphere.

The apparent loss of 18 percent of the present-day atmospheric oxygen over three billion years actually turns out to be just 2 percent because magnetic forces redirect most of the ions downward.
The Earth's upper atmospheric region is called the ionosphere and it is surrounded by and embedded in the magnetosphere -- a large cavity formed by the Earth's intrinsic magnetic field.

The ionosphere is a layer of charged particles created by the sun's intense ultra-violet light hitting Earth's upper atmosphere and ionizing the atoms within it -- primarily oxygen and nitrogen. It is these ionized oxygen atoms -- oxygen ions -- that are observed by low-altitude spacecraft to be accelerating upward out of the ionosphere in larger numbers. But spacecraft making measurements farther out in Earth's magnetosphere do not see the oxygen ions being lost in the same numbers -- instead the escaping flux is about an order of magnitude lower.

The researchers studied four escape routes of oxygen ions from the ionosphere and estimated "the net oxygen loss rate from Earth's atmosphere by determining the losses due to each escape route. The net oxygen loss rate could be estimated by subtracting the returning flux from the outflow flux" from the ionosphere. The researchers calculated that 90 percent of the oxygen ions that are measured escaping the ionosphere do not possess enough energy to escape the magnetosphere and are returned to Earth's low-altitude ionosphere, replenishing the atmosphere.

Magnetospheric processes facilitate the oxygen ion loss from the ionosphere, but the researchers propose that the magnetospheric processes "may also mitigate this loss by trapping ions and returning them to the atmosphere."

"Our understanding of the origin and evolution of planetary atmospheres hinges on knowing the composition, dynamics, source, and loss mechanisms operating at the present day," the researchers said in the paper.

Lead author Kanako Seki, a University of Tokyo student, did graduate research at Los Alamos and collaborated with Rick Elphic of the Space and Atmospheric Sciences Group. Other authors were from Rikkyo University, Tokyo, and the Institute of Space and Astronautical Science, Kanagawa, Japan.

Additional news releases related to Space Sciences

Additional news releases from the Nonproliferation and International Security (NIS)