Enceladus is the sixth-largest moon of the second-largest planet in the Solar System, measuring 310 miles in diameter. The surface is mostly covered in fresh, clean ice, making it one of the most reflective bodies in space. Little was known about it until the two NASA Voyager spacecrafts passed in the early Eighties.
However, Brian Cox revealed during his new BBC series “The Planets” how a bombshell discovery was made 25 years later.
In 2005, NASA’s Cassini probe came within 30 miles of the surface of Enceladus, discovering water-rich plumes venting from the south polar region.
Scientists found cryovolcanoes shooting geyser-like jets of water vapour, molecular hydrogen, other volatiles, and solid material, including sodium chloride crystals and ice particles, into space.
Dr Cox revealed why this find stunned scientists.
He said earlier this month: “Cassini has given us a glimpse beneath the ice of Enceladus and it is genuinely fascinating in a scientific sense because many biologists believe that hydrothermal vents like those are almost certainly present on the floor of Enceladus and they were the cradle for life on Earth.
“All the ingredients are present, there’s hot water in touch with ice and minerals that’s a reactive caldron of chemistry.
“There are reactive gases – methane – and Cassini found molecular hydrogen in the plumes and that was one of the food sources of primitive organisms on Earth.
“So there really is a possibility there is life in orbit around Saturn today.”
However, while enthusiastic about the find, Dr Cox explained to viewers why life near Saturn would be in its very early forms.
He added: “The prospect of life on Enceladus is exciting, but if it is there, it’s likely to be only the simplest and most primitive of organisms.
“And given how violent and changeable Saturn’s past has been, this world of ice and liquid water may only have arisen relatively recently.
“We don’t know how long Enceladus has been geologically active, how long its had an ocean.
“If it was only tens of millions or even hundreds of millions of years, that may not have been enough time for life to get going.
“But if there is life, then we can glimpse its future because there are still hydrothermal vent systems present on Earth today and life doesn’t just survive there, it thrives.”
Dr Cox revealed during the same series why Venus too could be hiding basic forms of life.
Venus is by far the hottest planet in the Solar System, with a mean surface temperature of 500C even though Mercury is closer to the Sun.
However, Dr Cox revealed things could not have been more different a few billion years ago.
He explained: “At the time when life was just about beginning on the Earth, three-and-a-half to four billion years ago, the Sun was fainter and that means that Venus was cooler.
“In fact, temperatures on Venus at that time would have been like a pleasant spring day here on Earth.
“Within a few million years of its formation, the surface of Venus had cooled and the planet found itself at just the right distance from the faint young Sun for Venus to experience a sight familiar to us here on Earth.
“The heavens opened and great torrents flooded the surface, rivers of water flowed and Venus became an ocean world.
“The planet’s atmosphere allowed it to hold on to the oceans by acting as a blanket, keeping the surface temperate thanks to the greenhouse effect.”