NASA began observing a dust storm on the planet Mars on November
10, 2012. Martian dust storms are the largest such storms in our
solar system. Over the century that astronomers have monitored
them through telescopes – and now via spacecraft – these
periodic storms have been know to rage for months and grow to
cover the entire planet Mars. This one, however, appeared to be
dissipating by early December, 2012. Dust storms on Mars
sometimes start in the months before Mars is closest to the sun,
as it soon will be. Mars will reach perihelion – its closest
point to the sun – in January 2013. Each Martian year lasts
about two Earth years. Regional dust storms expanded and
affected vast areas of Mars in 2001 and 2007, but not between
those years and not since 2007. The image above is a mosaic
taken by a spacecraft in orbit around Mars, the wonderful Mars
Reconnaissance Orbiter, on November 18, 2012. Small white arrows
outline the area in Mars’ southern hemisphere where the 2012
Martian dust storm was building. The