Limerick astro club - the main hope for extra terrestrial life is...

On a clear night you can clearly see the planet Jupiter shining brightly with the naked eye.

If you manage to get a closer look through a telescope, you can see tiny flecks of light orbiting it.

The discovery of Jupiter’s four large moons, Io, Europa, Ganymede and Callisto, known as the Galilean moons, transformed the way in which the universe was viewed. This was the first time that celestial bodies were seen revolving around an object other than Earth.

While Jupiter has some amazing qualities, it’s one of its moons that holds some hope for discovery of life outside of earth.

Europa is about 90 % the size of Earth’s Moon, so if it replaced our moon it would appear nearly the same size within the sky. However, a major difference would be the brightness that we would notice, as Europa’s surface is made of water ice and so it reflects over five times the amount of sunlight than does our own moon. Europa takes about three and a half days to orbit Jupiter and it’s locked by gravity to Jupiter, so the same hemisphere of the moon always faces the planet.

Due to its brightness reflected through ground-based telescopes, scientists knew that the surface of Europa was primarily water ice. Furthermore scientists have determined that beneath the ice crust is an ocean of liquid water or slushy ice. Scientists believe that Europa’s outer ice sheet is 15 to 25 kilometres thick which floats on an ocean 60 to 150 kilometres deep.

While Europa is about a quarter the width of Earth, its ocean may contain almost double the amount of water as all of Earth’s oceans - making it one of the most promising places to look for life beyond Earth.

Between 1995 and 2003 NASA's Galileo spacecraft explored the Jupiter system and highlighted the changing surface of Europa; it discovered peculiar pits and domes that indicate this ice layer could be slowly going through a convection process. This is when cooler, denser ice sinks, while warmer less-dense ice rises due to heat from below.

Long fractures which are often only 1 to 2 km wide but can extend for thousands of km across Europa’s surface are evident. So while we all want to see the planets, moons can be just as interesting.

Limerick Astronomy Club meets the first Thursday of every month in room G10 in Mary I: email limerickastronomyclub @gmail.com