What is the mission of NASA's Aura satellite?

Launched on July 15, 2004, the Aura satellite is on a mission to monitor changes in the Earth's atmosphere, particularly the ozone layer. Instruments on the satellite measure the chemistry and dynamics of the upper atmosphere. The data it will gather will be used to predict alterations in air quality and climate change.

Why is there a hole in the ozone layer?

The ozone layer is not evenly distributed around the planet. It is thicker around the equator and nearby latitudes and thinner as one progresses north and south. This is true of the Earth's atmosphere in general because the planet's spin causes the planet to bulge slightly around the middle; the gravitational pull is consequently a little weaker and the atmosphere thickens. At the poles, the atmosphere is thinner, including the ozone layer. In addition, because ozone is dependent upon the interaction of sunlight and oxygen, there is naturally less ozone at the poles; furthermore, ozone layers fluctuate naturally over time due to numerous factors affecting climate and sunlight levels.

Since 1975, scientists believe that more than 33 percent of the ozone layer has disappeared. There is a seasonal factor to the reduction in ozone at any given time during the year, too. At different times, the ozone layer naturally declines or rises. But scientists also know that chlorofluorocarbons (CFCs), which are used for air conditioning, aerosol sprays, and halon in fire extinguishers, along with methane (CH4) and nitrous oxide (NO2), are broken down by UV radiation, freeing carbon, chlorine, and nitrogen atoms that then react with ozone molecules and destroy them. CFCs are particularly bad because they last so long in the atmosphere. One CFC molecule can destroy 100,000 molecules of ozone!

Who helped link CFCs to the destruction of the ozone layer?

Mexican atmospheric chemist Mario J. Molina (full name, José Mario Molina-Pasquel Henrfquez [1943-]) and American atmospheric chemist Frank Sherwood Rowland (1927-) are generally acknowledged as the scientists who first explained how chlorofluorocarbons were destroying the ozone layer. A paper they published together in 1974 first explained how the process works about four years after scientists began to understand that ozone levels were declining in the upper atmosphere. The result of their work led the United States government to ban CFCs in aerosol cans in 1978.

How was the ozone hole discovered?

The famous meteorologist Gordon Miller Bourne Dobson (1889-1976) was the first to make accurate measurements of the ozone in the 1920s, but it wasn't until 1979 that the depletion of the ozone was observed at the South Pole by the Nimbus 7 satellite. Today, a network of "Dobson spectrophotometers" have been set up around the world to monitor changes in the ozone.

Is the hole in the ozone layer causing frog species extinctions?

Biologists have known for a long time that frogs are very vulnerable to changes in their environment. Frogs across the globe were being found with deformities, such as extra legs, and species were going extinct. By the mid 1990s, it was still being speculated that the cause of the mutations was the weakened ozone layer, which was allowing too much ultraviolet radiation to filter onto the planet. Today, however, most scientists believe that the culprit is fertilizers leaking into the lakes and rivers where frogs live. The fertilizers

A Dendrobates tinctorius, or species of dart poison frog, is one of many frog species in danger of extinction for many reasons, some of which are related to environmental changes.

cause certain types of snail species to thrive, and these snails often host parasites. The parasites, in turn, infect frogs when they are still in their tadpole stage. Cysts form on the tadpoles, which creates the mutations that are being observed.

Besides the malformations seen in frogs, there is another, even more troubling concern: many species of frogs—some estimate about 100 species are vulnerable—are threatened with extinction, and many others have already disappeared. In this case, the culprit is global warming. Because frogs have thin skin, they are vulnerable to environmental changes. Increased temperatures have caused fungi—some scientists specifically blame the chytrid fungus—to infect frog skin, and this leads to the lethal disease Batrachochythrium dendrobatidis (BD). The good news is that it is easy to treat and cure frogs; the bad news is that, even if they are treated, once released back into the wild they are likely to be reinfected. To help arrest the extinction rate, zoos around the world have been rescuing sample populations and breeding them in captivity.

Why is there an ozone hole at the South Pole but there isn't one at the North Pole?

The harmful chemicals that destroy the ozone layer have to be carried up into the stratosphere by clouds in order to react with ozone. The land mass at the South Pole (Antarctica) creates the necessary weather conditions for this to happen, while the North Pole is covered in water, causing winds in the upper atmosphere to blow away pollutants. The bad news is that some scientists fear that increasing levels of pollution may result in a hole in the ozone at the North Pole in about 20 years.

How big is the hole in the ozone?

In 2007 the ozone hole was measured to be 9.3 million square miles (24 million square kilometers) in size. But this was a smaller hole than the record, set in September 2006, when the ozone hole was a gaping 10.6 million square miles (27.5 million square kilometers) in area.

Can the ozone hole be healed?

Yes. While the latest figures represent an increase in the ozone hole's size over previous years, there is some good news: compared to the 1980s, the hole is expanding more slowly. If we continue to reduce pollutants, the expansion may eventually stop and be reversed. Scientists believe that, if this happens, it will take about 50 years for ozone levels to return to natural levels.