Jenny Hayes investigates the mysteries within At-Bristol Science Planetarium.

Now, readers, I know that we have travelled to Jupiter before in the course of this series – and even gone so far as to land on four of its moons – so you may well be wondering why we are once again returning to visit the gas giant. Well, it’s because last time I omitted some rather vital information. Now, let me explain. It wasn’t my intention to mislead you in the previous article, but rather not to alarm you. For, you see, it may very well be that we are not alone in the solar system.

Although Jupiter itself is unlikely to be able to support life, one of its satellites may well do. Europa, the fourth largest moon of Jupiter, was discovered by Galileo when he first trained his telescope on the planet back in 1609. What he saw shook the scientific community to its core. He observed Europa – alongside Jupiter’s other large moons Io, Ganymede and Callisto – orbiting the planet, just as our moon orbits us. From this, Galileo was able to prove the earth-shattering theory that we are not in fact the centre of the universe around which everything else revolves, but rather just one of many celestial bodies orbiting the sun. But that isn’t the end of Europa’s revelations…

In 1979, NASA’s Voyager 2 spacecraft gave us our first close encounter with the moon, capturing images of a strange, icy world whose surface is scarred by scores of burnt orange tiger stripes. And it is these vivid streaks that hold the clue to the possible existence of life on Europa, as scientists believe they are mineral deposits – darkened in colour as a result of the radiation emitted by Jupiter – which have bubbled up from an ocean beneath the icy shell of the moon.

If evidence of life is found during this mission to Europa, the repercussions will be as sensational as those following Galileo’s discovery of the moon over 400 years ago.

Although Europa is about 485 million miles from the sun, with a temperature that peaks at a rather nippy -160˚C, the presence of liquid water is possible due to the energy created by tidal flexing as the moon orbits Jupiter and moves into the proximity of the other high mass moons. This energy generates heat at Europa’s core, which scientists believe breaks through into the ocean above via hydrothermal vents of geothermically heated, mineral rich water similar to those found here on Earth. If this is the case, then it is highly likely that, just as on our own planet, these vents are hotbeds of life that contain anything from microbial organisms to primitive fish.

Coupled with the possibility of hydrothermic activity, scientific evidence suggests that hydrogen peroxide is abundant across much of the surface of Europa’s moon. Because this decays into oxygen and water, some experts have suggested it could provide a further energy supply for simple life forms.

But it is any of this actually possible to prove? Well, if anyone can, then it’ll be those clever folks at NASA, and rest assured they are rising to the challenge. In June 2015, the space agency announced its plans to develop an unmanned, radiation-tolerant spacecraft that it will send up to Europa in the early 2020s. Because the levels of radiation on Europa are of face (and metal) melting proportions, this probe will not orbit the moon itself, but instead take a long, looping orbit around Jupiter that will allow it to make 45 flybys of the moon.

The spacecraft will contain a wealth of specialist instruments designed to capture data for NASA back on Earth. Cameras and spectrometers will take detailed, high resolution images of Europa’s surface and examine its composition, while an ice penetrating radar will determine the thickness of its icy crust and if an ocean is indeed present beneath it. If one is found, the onboard magnetometer will be used to measure the strength and direction of the moon’s magnetic field so that the team at NASA HQ can determine both the depth and salinity of the body of water.

Hubble-telescope-2009-by-NASA

An image of the Hubble Space Telescope, which captured images of suspected plumes of water vapour at Europa’s south pole.

As the Hubble Space Telescope also observed what could be plumes of water vapour exploding from Europa’s south pole in 2012, there will be further instruments onboard the probe that are capable of analysing the composition of these droplets. If indeed they have spewed up from an underground ocean beneath the moon’s surface, this will allow scientists to assess the viability of life in the water below without having to drill through layers of ice. Not only does this minimise the risk of contaminating this pristine place, it is also great news – as we are no way near designing a machine with the capability to bore through the 15 miles of ice that encase the ocean beneath.

If evidence of life is found during this mission to Europa, the repercussions will be as sensational as those following Galileo’s discovery of the moon over 400 years ago. After all, if life originates elsewhere in our own solar system, then it must surely exist elsewhere throughout the galaxy and beyond.

Jupiter is well placed in the southern sky this month, and you’ll be able to discern the distinct bands on the planet and its four largest moons using either a telescope or a good pair of binoculars mounted on a tripod for stability. And, when you spot Europa, don’t forget to give a little wave – after all, it may be home to our first set of extra-terrestrial neighbours.


 

With thanks as always to Lee Pullen for sharing his time and knowledge. If you’ve been inspired to learn more about the stars this winter, then head down to the Planetarium to catch the excellent Winter Stargazing show in 3D – it’ll blow your mind. For more details, telephone: 0117 915 1000 or visit: www.at-bristol.org.uk