In the sandy desert and Savannah Namibia, South Africa, mysterious circles, known as "community spirit", which appear and disappear after several years without any apparent cause. A new look at these strange circles not solve their mystery, but at least shows that the greatest of them can last a lifetime.

The smaller circles spirits are kept in average 24 years, while large, there are to 75 years, according to a report published in the journal PLoS ONE". However, the study still sheds little light on why circles are formed there and then disappear in the landscape decades later.

"The question "Why?" is very complicated," says researcher Walter Kinkel, a biologist from the University of Florida. "There are several hypotheses, and none have no enough convincing evidence".

Circles of life (and death)

Cancel interested in circles spirits in 2005 during the Safari through the nature reserve Namib Rand in the South-Western Namibia, in the desert of Namibia. It was his first meeting with the circles on the ground, tens of thousands of which can be seen in the red sandy soil in this region. Shortly after the appearance of a circle around the boundary grows tall grass, clearly signifying nothing.

Very few researchers study circles spirits, mostly due to their remoteness (180 kilometers from the nearest village). This arid area, in which are found antelopes, ostriches, leopards and other large animals.

"It's as if you died and were in heaven - if you love the remote, beautiful wilderness," says Cancel.

At first glance, he suggested that circles underground termite nests-gatherers. But excavations have shown the absence of any signs of termite nests underground. Other possible explanations, such as the difference in the composition of nutrients in the soil or death of vegetation due to the toxic fumes, also was not confirmed.

In fact, little is known even about the cycle of existence of these circles, says Cancel. With the help of personnel of the nature reserve, satellite imagery and aerial photography, he has aimed to change the situation. Comparing satellite images of 2004 and 2008, he found that circles stable enough, occur almost immediately in the maximum size, or quickly grow to full size just appeared. The smallest is about two meters in diameter, the largest - about twelve. Winds blow away the soil with empty circles, turning them into a small decrease. Sooner or later the plants back into place again settling circles and leaving only faintly discernible trace of the "Ghost circle".

Considering that the total number of laps spirits on the landscape is fairly stable, Cancel used satellite imagery to assess how fast circles pass the stages from emergence to maturity and to revegetate. It is possible to make a rough estimate of life expectancy circles. Most of them probably exists from thirty to sixty years, says Cancel.

The continuing mystery

Cancel managed to hold these estimates thanks to help from the Natural reserve of the Namib Rand, which sells custody for circles spirits. Sponsored circles are marked with ceramic plate, and their exact GPS coordinates are recorded. For ten years of the program of care, staff monitors sold circles. Their data indicate the same age range for circles spirits, who brought Cancel on the basis of satellite images.

He also determined that the circles are formed only on sandy soils with a minimum of stones, and that they are not formed on the moving dunes or alluvial layers, where the Sands are applied water.

Some of the experiments of Kinkala continue to go right now, but still they did not shed any light on the origin of the circles. Cancel believes that the circles are the product of some form of natural self-organization plants.

"There are several mathematical models, which are based on the idea that plants can extract the resources for themselves what has a positive effect on plants at the place where they grow, but negative in more remote plants," he says.

According to him, the computer models, based on these calculations, can generate landscapes that are slightly reminiscent of the field circles spirits in Namibia. But even if this hypothesis is on the right path, it does not explain how plants make these patterns, even when the soil of nutrients and some other possible factors already excluded.

With the very small number of scholars who study circles - and without sponsorship aimed at unlocking secrets of the landscapes of South Africa - Kinkel says that circles the spirits with a high probability will remain a mystery.

"And I don't think this mystery will be solved in any time soon," he says. And the constancy of this mystery makes it even more intriguing.

"It is a science, isn't it?", says Cancel. "If you knew the answer in advance, it would be not so interesting."