Since 1979, when the Voyager probes flew past Jupiter and its system of moons, scientists have speculated about the possibility of life within Europa. Based on planetary modeling, Europa is believed to be differentiated between a rocky and metallic core, an icy crust and mantle, and a liquid-water ocean that could be 100 to 200 km (62 to 124 mi) deep. Scientists theorize that this ocean is maintained by tidal flexing, where interaction with Jupiter's powerful gravitational field leads to geological activity in Europa's core and hydrothermal vents at the core-mantle boundary.

Investigating the potential habitability of Europa is the main purpose of NASA's Europa Clipper mission, which will launch on October 10th, 2024, and arrive around Jupiter in April 2030. However, this presents a challenge for astrobiologists since the habitability of Europa is dependent on many interrelated parameters that require collaborative investigation.

In 1963, six years after the first satellite was launched, editors from the Encyclopedia Britannica posed a question to five eminent thinkers of the day: "Has man's conquest of space increased or diminished his stature?" The respondents were philosopher Hannah Arendt, writer Aldous Huxley, theologian Paul Tillich, nuclear scientist Harrison Brown and historian Herbert J. Muller.

Sixty years later, as the rush to space accelerates, what can we learn from these 20th-century luminaries writing at the dawn of the space age?

The state of space 60 years on

Much has happened since. Spacecraft have landed on planets, moons, comets, and asteroids across the solar system. The two Voyager deep space probes, launched in 1977, are in interstellar space.

A handful of people are living in two Earth-orbiting space stations. Humans are getting ready to return to the moon after more than 50 years, this time to establish a permanent base and mine the deep ice lakes at the south pole.

There were only 57 satellites in Earth orbit in 1963. Now there are around 10,000, with tens of thousands more planned.