The Earth's magnetic field protects against solar winds that would otherwise wipe away the atmosphere from our planet, researchers announced Thursday.

The conclusion came from a chance alignment between Mars and the Earth that allowed astronomers to determine how a solar flare affected both environments.

Solar winds blew 10 times more oxygen off the Martian planet, which lacks a planet-wide magnetic field, than Earth, researchers found.

The idea that the Earth's magnetic field helps keep the atmosphere from being whisked away has theoretical support, but the current study is the first time astronomers observed the magnetic effect in action.

The shielding effect of the magnetic field is easy to understand and to prove in computer simulations, thus it has become the default explanation, Yong Wei, researcher at the Max-Planck-Institut für Sonnensystemforschung, Germany and study leader, said in a statement.

The chance alignment between the Earth and Mars took place Jan. 8, 2008.  The European Space Agency captured atmospheric data from Earth and Mars using their Cluster and Mars Express missions.

The researchers found that solar winds hit the two planets with the same force, but Mars bore the brunt of atmospheric loss.

Over billions of years, such events could lead to huge losses of Martian atmosphere, the astronomers said.

The Journal of Geophysical Research published the research online Wednesday.

The next step researchers plan is is to test Venus, a planet with no magnetic field but that shares a similar size to Earth and has a thicker atmosphere, the researchers said.

Luckily for researchers, the Earth, Mars and Venus are set to align June 6, which will astronomers to make the observation with ESA's Venus Express.

For the next few months there is a good alignment between the Sun, Earth, Venus and Mars, and observations made by many spacecraft, including Mars Express, Venus Express and NASA's STEREO solar observatory, will be analyzed together, Olivier Witasse, ESA Mars Express scientist, said in a release.

Reference: http://dx.doi.org/10.1029/2011JA017340