NASA's satellite data found that the ozone hole in the stratosphere over Antarctica is slightly smaller this year.

The ozone depletion has been observed since the late 1970's and this phenomenon commences from August and September, through the spring in Antarctica. The average size of the ozone hole was found to be about 8.1 million square miles in September-October 2013. This size has expanding after going up to 8.7 million square miles in the mid-1990s.

"There was a lot of Antarctic ozone depletion in 2013, but because of above average temperatures in the Antarctic lower stratosphere, the ozone hole was a bit below average compared to ozone holes observed since 1990," Paul Newman, an atmospheric scientist and ozone expert at NASA's Goddard Space Flight Center in Greenbelt, Maryland, stated in a press release.

This ozone layer depletion in the atmosphere is caused by chemicals consisting of chlorine and/or bromine, according to British Columbia. These ozone destroying elements are termed as 'ozone-depleting substances' (ODS). They are eco-friendly, stable and harmless. The stability of these substances makes them rise upwards and reach the stratosphere, the strong U.V. rays then break the substances and they discharge unstable chlorine and bromine molecules which pierce the ozone layer by reacting with the ozone molecule. One chlorine molecule is capable of breaking down thousands of ozone molecules rupturing the layer.

In 1987, the Montreal Protocol was formed by concerned nations to shield the ozone layer from further depletion. Efforts were made to limit the production of ozone-depleting chemicals. Concerted efforts resulted in the reduction of these harmful chemicals in the atmosphere. This resulted in the stabilization of the hole.

This seasonal phenomenon reached the maximum size of 9.3 million square miles on Sept.16, 2013, which is equal to the size of North America. The biggest size this hole attained is 11.5 million square miles, on Sept. 9, 2000.

Scientists from NASA and the NOAA (National Oceanic and Atmospheric Administration) have been examining the ozone layer with the help of various instruments and satellites 1970 onwards, trying to figure out different aspects of the ozone depletion.

NASA explained that it is too soon to conclude whether this hole stated healing itself.