Exoplanets

In 1610 Galileo Galilei an Italian astronomer pointed his telescope towards the sky. His discoveries have forever changed our understanding of the cosmos. He looked at the moon and saw a landscape with mountains and valleys. He looked at the gas giant Jupiter and he saw moons orbiting the planet. He believed that smaller bodies were revolving around bigger and that the Earth and the planets were orbiting the Sun. Heliocentrism that was proposed by Copernicus in 1543 was considered by the Roman Inquisition as foolish and blasphemy and Galileo was sentenced to spend the rest of his life in house arrest. Galileo was employed as a mathematics tutor for Cosimo de' Medici and he named the moons Medician Stars and called them Jupiter I, II, III and IV. But Simon Marius a German astronomer that discovered the Moons independently at the same time. Named them Io, Europa, Ganymede, and Callisto after Zeus mistresses. Galileo's names were used until the mid-20th century when more inner moons were discovered.

Credit:NASA/JPL/DLR

The unmanned spacecraft Galileo was named after Galileo Galilei was launched in 1989 it arrived at Jupiter in 1995. It was the first mission that investigated Jupiter's moons and Galileo was in the Jupiter system for 8 years until it was terminated by falling into Jupiter's atmosphere in 2003. The data the spacecraft collected supported the idea that there is a liquid ocean of water under the moon Europa's icy surface. The ocean is bigger than all the water on Earth and the moon is geologically active due to tidal forces from Jupiter's gravitation. Vulcans will heat the ocean, and energy and water are the building blocks of all living organisms. Considering that the ice surface is 20 kilometers thick then the pressure in the ocean could be calculated using Europas surface gravity and density of ice \(g_{eu}\rho _{ice}s=\)1.315 m/s² *917 kg/m3* 20000 m = 24 Mpa or 240 bar

Deep-sea creatures can live at 20 to 1000 bars on earth. Also, the temperature should be similar and the thick ice blocks the deadly radiation from Jupiter. This makes Europa the best candidate for looking for life in our solar system
The Hubble telescope discovered in 2014 indications that there are geysers shooting out water in space from Europa's icy surface. 

Nasa will send a probe called the Europa clipper in 2025. The clipper will not be orbiting the moon as radiation from Jupiter could damage the electronic instruments on the probe. Instead, the clipper will make 45 flybys in one of those flybys the probe could catch one of those geysers and analyze the molecules in the gas for living organisms. The probe will be equipped with advanced instruments that will scan the surface and with radar map the thickness of the ice surface. It could help to find pockets of water closer to the surface and also investigate what could be a good spot for a lander. It is also suggested that the mission will include a lander that will be financed by the congress. Drilling through the 15-20 kilometer would be very technical hard and expensive, but if the clipper finds interesting results then perhaps the next mission will be launching a submarine under its surface and perhaps we could find some alien fish or mermaids.

European Space Agency is also planning a mission to Europa, Ganymede, and Callisto. All three moons might have significant bodies of liquid water beneath their surfaces. The JUpiter ICy moons Explorer is an interplanetary spacecraft that will launch in 2022 and reach the system in 2029 it will end up orbiting the moon Ganymede in 2033.