I fortuitous planetary alignment between Earth and Mars in 2008 allowed scientists to study the effects of planetary magnetic fields – or the lack of. Unlike Earth, Mars has no magnetic field.
So, when a stream of solar wind composed of potentially damaging, high-energy particles hit both planets during alignment, scientists measured how much oxygen was lost by each. What they predicted was that Earth’s magnetic field would act as a shield and deflect the solar wind.
What they found was just that. As the pressure of the solar wind increased, Mars lost ten times more oxygen than Earth. Scientists believe that over extended periods of time, say one billion years, solar winds could significantly reduce oxygen content.
In addition to no magnetic field, Mars has an extremely thin atmosphere. In order to test the atmosphere’s role in protection against solar wind, future experiments will involve comparisons between Venus and Earth. However, the researchers must wait for an alignment between Venus and Earth to make the comparison.
For more information you may read the press release.