Destination: Jovian Moons

This year, why not make the most of your holiday and head off for a few weeks somewhere really far flung? In the latest installment of our space travelogue series, Helen Potter talks you through a trip to Jupiter's moons.

Does it seem like everyone has been to Mars and Venus (and shown you their pictures)? Are the once remote reaches of the asteroid belt full of gap year students? Did the opening of Butlins on the Moon disturb the Sea of Tranquility forever?

Never fear, there is an alternative. A trip taking in all four Galilean Moons of Jupiter showcases this most spectacular of planets while avoiding the crowds of tourists around the Great Red Spot.

Getting there and away

Jupiter is a long haul, a year and nine months away at current rocket speeds or 35 minutes at the speed of light. Sometimes budget spacelines use the gravitational pull of the sun for a slingshot effect but this is merely to save fuel and significantly increases the travel time to four to six years, so that's best avoided.

Callisto

Callisto: the skater's paradise.

Callisto is the first stop on our package tour; the outermost of our four moons and the third largest moon in the Solar System. Orbiting at approximately 1.8 million kilometres away from Jupiter, Callisto is one of the most cratered objects in the Solar System. In fact, any new craters would have to form on top of old ones.

The most impressive feature on this moon is undoubtedly the huge hollow named Valhalla - at an impressive 3000+ kilometres across, it has become particularly popular with skateboarders who use the uneven terrain and barely-there atmosphere of CO₂ to pull off some impressive stunts.

Ganymede

From Callisto it’s only a short hop to Ganymede, the largest moon in the Solar System; this giant satellite is bigger than Mercury. Furthermore, it is the only moon that's known to have it's own magnetic field.

Three of Jupiter's moons exhibiting Laplace resonance where the moons' gravitational effects on each other keeps them locked into the same orbits.

The orbits of Ganymede and the two inner moons Europa and Io are locked in a phenomenon known as Laplace resonance. For every orbit that Ganymede makes around Jupiter, Europa makes exactly two and Io exactly four, leading to changes in the shape of the moons during their orbits as Jupiter's gravity stretches them out on each approach. This heats the interiors of the moons by friction and gives rise to some of the spectacular features that await you.

Ganymede's uneven surface of ice and thin oxygen atmosphere have made it an ideal setting for winter sports, although with a temperature of -172 degrees Celsius, it is advisable to wrap up warm.

Europa

Europa will give you plenty of chance to exercise your brain.

Europa is a similar size to Earth and boasts one of the smoothest surfaces in the Solar System. If the prospect of the galaxy's largest curling arena does not appeal to you then your time would be well spent exploring and attempting to solve the mystery of the dark streaks that criss-cross Europa’s surface. Are they caused by the gravitational pull of Jupiter? Are underwater volcanic eruptions to blame? Or are they bacteria growing in the liquid water underneath the surface; the first traces of extra-terrestrial life?

If scientific discovery and a place in the history books float your boat then Europa is not to be missed.

Io

Io is a colourful world of fire and brimstone.

After the ice of the outer moons, the fiery surface of Io makes a spectacular ending to this tour. The most geologically active object in the Solar System, Io has over 400 active volcanoes, some of which are taller than Mount Everest and capable of spewing out columns of sulphur and sulphur dioxide 500 km high. The volcanic flows and lava plumes paint the surface an exotic mix of yellows, greens, blacks and reds.

In addition, the magnetic field of Jupiter sweeps up dust and gases at a rate of 1 tonne per second, stripping Io’s thin atmosphere of sulphur dioxide and leaving it to be constantly replenished (hold on to your hats).

Io also serves as an excellent viewpoint to take in the majesty of Jupiter. With an orbital period of just 1.75 days and the same face always pointing at the planet, you can literally sit back and watch the gas giant go by before heading back to the comparatively tame delights of Earth.

In conclusion, the Galilean moons have it all. Whether it's hot, cold, smooth or bumpy you're after, you'll find a satellite to suit your every need.

Try this if you like Helen's style... or try another cosmic destination:

Pluto: party central
Saturn: a journey to test your patience
Venus: mistaken for a UFO

Images: NASA
Animation: W

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Destination: Jovian Moons