Keep a base in Antarctica is important to do research in extreme conditions and to understand more about how our planet works.
But there is a third reason for the country to maintain a base on the continent apart from the high seas, Antarctica is the last place on earth without an owner. And it's a great place: 10% of the whole field of the earth (if it were a country it would be bigger than China or Brazil and the U.S. second only to Russia).
As all unclaimed, the big question is who will belong. And there are several way to determine who will own that space.
Unlike Brazil or Australia, which already had inhabitants when the Europeans 'found', there was no one in Antarctica when it was first visited. Therefore, the most obvious solution would be that the continent belonged to the first to find her. But such a solution is impossible because no one knows exactly who was the first to find the continent. The most likely hypothesis is that they have been Scottish and American whalers. But as sailed in secret, never said where it really had been.
Another solution is - as in Brazil or Australia - on the first country to colonize. But there is another problem here: nobody has ever colonized the continent because it is permanently uninhabitable. You can set up a base in place, and even spend a year or two there, but always depend on foreign aid. And no 'changes to the Antarctic', contrary to what was done in all places colonized. If this has not precluded this solution, several countries began to send explorers to the continent at the same time (Japanese, Norwegian, British, etc.). Therefore, this solution is also difficult to be adopted.
But there are two solutions that do not look at historical data, but in technical details and current.
The first is to use a system similar to the one used to determine who owns the territorial waters, following the lines converging longitudinal Antarctica. It works like this: you turn the globe so that Antarctica is directly in front of you and see what countries are in the neighborhood. Below a small example using Google Earth below.
But using this method, there is a big political issue: the economic and military great powers - Russia, USA, China etc. - are almost all in the northern hemisphere, and therefore have almost no right to any area, and this hampers agreement. (The 'almost all' is because nations like France and the UK have islands under its protectorate over the southern hemisphere. This explains, for example, that the Falkland Islands are so important to the UK).
The other solution is to simply divide the continent among those who have interest in it. And what better way to demonstrate interest than look at who is based in the continent? So all countries who want to be able to have a portion of the continent has a base there, including Brazil.
And, after all, what solution is used?
No one knows. Since 1959 the Antarctic Treaty halted attempts to divide the continent and established that until a solution is found, the use of the continent is free for all, provided they respected certain limits, a ban on military bases, weapons testing , nuclear explosions or disposal of radioactive wastes.
Por que ter uma base na Antártica é importante juridicamente? | Poder Naval - Marinha de Guerra, Tecnologia Militar Naval e Marinha Mercante