On June 1st of this year, the European Space Agency’s (ESA) Mars Express spacecraft was able to capture images of an unusual alignment as Mars’ moon Phobos passed in front of Jupiter (seen in background). The images were put together to form this amazing animation.
Mars has two moons – Phobos and Deimos. The origins of these names are a bit gloomy : Phobos, named after a Greek God, means “fear” and Deimos is a figure representing “dread” in Greek mythology. Phobos is the largest of the two, and the closest moon to Mars.
You can see quite clearly that Phobos has an irregular shape – it’s mean radius is only of 11.1 km (6.9 mi). Compare that with our Moon with its mean radius of approximately 1737.5 km (1079 miles). And that seemingly small object behind Phobos is of course Jupiter with a mean radius of (a not so small) 69,911 km (or 43440 miles).
This was a unique opportunity for the Mars Express spacecraft which performed a special maneuver to capture the alignment. At the time these images were taken, there was a distance of 11,389 km (7076 miles) between the spacecraft and Phobos with Jupiter a further 529 million km away.
The Mars Express spacecraft was launched in 2003 and consisted of two parts – the Mars Express orbiter reponsible for the images in the animation above and the Beagle 2 – which was to land on the Martian surface and study the planet’s geochemistry. Sadly the ill-fated Beagle 2 failed to make a safe landing (reminding us that planetary exploration is not easy!). The Mars Express, however, has been collecting valuable data since 2004. In particular, experiments are looking at the atmospheric environment, studying the distribution of water vapour, imaging and analysing the surface composition of Mars and searching for possible ice below the planet’s surface.
The science return and flexibility of the Mars Express has earned it significant mission extensions – in fact it was initially planned to have a mission length of one Martian year (that’s 687 days for we earthlings). It is now expected to continue its operations until December 2012. Find out more about the mission at ESA’s site http://www.esa.int/SPECIALS/Mars_Express/index.html.