Enceladus, Saturn’s sixth largest moon, is, according to some, the most exciting object in the solar system. It has a warm, salty ocean 20 kilometers below its icy surface that appears to be potentially habitable.
Could there be some kind of alien aquatic life in Enceladus that evolved completely separately into life on Earth?
This is a matter of utmost importance in the planetary science and astrobiology communities. So much so that pressure is mounting for NASA to send a flagship mission to Enceladus to find out exactly what’s going on under the tiny moon’s icy crust.
It’s a question currently being examined as part of the Decadal Survey for Planetary Science and Astrobiology, a report compiled by the National Academy of Sciences that will set NASA’s priorities for the next 10 years. It will be released on April 19, 2022.
Will the amazing “Orbilander” mission make it on this list?
A concept for a flagship NASA mission costing around $3 billion, Orbilander would see a single spacecraft first orbit Enceladus and then land on it.
“Enceladus is home to the best-characterized ocean in the solar system, second only to Earth’s,” said Shannon M. MacKenzie, a planetary scientist at Johns Hopkins University’s Applied Physics Laboratory and author of the Enceladus Orbilander mission concept. Enceladus has a source of heat and liquid water and we know that these two things combine to create an incredibly intriguing diversity of life on our planet. So why not on Enceladus? “There’s liquid water there and the chemical ingredients that we think biochemistry needs, but it’s very difficult to use the typical tools that a satellite would need to interrogate that ocean because it’s under miles of ice,” MacKenzie said.
Ah yes, the ice cream.
Scientists have known Enceladus has a 30-kilometer-deep subterranean ocean since 2014, when data from NASA’s Cassini spacecraft revealed the tiny moon has Yellowstone-style geysers that erupt through cracks in the ice. “There are these 10-kilometer long fissures at the south pole that contain these individual jets that are spewing material from the ocean into space,” MacKenzie said.
Scientists call them “tiger stripes” and they look like this:
These geysers theoretically allow a spacecraft to sample its subterranean ocean without having to pass through its ice crust.
“The incredible images of Enceladus by Cassini helped peel back the layers of what’s going on,” MacKenzie said. “We are now able to prove that Enceladus is a potentially habitable environment.”
This ocean is probably heated by the moon’s core; landmark theories about hydrothermal vents – like those found on Earth – that could support life.
A recent study suggests that the subterranean ocean of Enceladus seems to stir currents like those of the Earth’s oceans. Another that it hosts ice quakes. There is also intriguing evidence of water-rock interactions occurring at the base of the ocean.
“If I had to put my money on anything in the solar system that would be a slam dunk to get the information we need and say life exists, it would be Enceladus,” said lead and lead scientist Dr Jackie Faherty. Principal of Education jointly at the Department of Astrophysics and the Department of Education of the American Museum of Natural History. “You don’t have to dig a hole – these exploding geysers shoot out this material for a spaceship to stick out its tongue to take a lick… Enceladus is the most exciting object in the solar system.”
However, Orbilandre would like to land on Enceladus. “Orbilander is going to go and sample these plumes – actually ice particles in space that came out of these cracks – about twice a day for 200 days, and then it’ll land,” MacKenzie said. “That’s because the bigger particles aren’t going to go up high – they don’t have enough kinetic energy – so they fall back to the surface.”
In fact, landing on Enceladus will be easier than on, say, Mars, because as a much smaller body there’s a lot less gravity – about a hundredth that of Earth.
The main problem with the Orbilander mission concept is that Enceladus is so tiny. It’s only 311 miles/500 kilometers in diameter, about one-seventh the size of our Moon, so physically breaking out of Saturn’s orbit and orbiting Enceladus won’t be easy. “One way is to carry a lot of fuel, but that’s expensive,” MacKenzie said. In dollars, yes, but also in terms of mass – the bigger the spacecraft, the slower it will move. “Another is to take advantage of gravity assists and take a ‘moon tour’ in the Saturn system,” MacKenzie said.
No mission to Enceladus will take place tomorrow, whatever the Decadal Survey recommends NASA do. The Orbilander concept proposes a launch in 2038 and an arrival in 2050 to begin a 200-day orbit. Once samples of the plumes have been taken for “life detection”, a suitable landing spot can be found.
Is 2050 too far away for anyone to get excited about Enceladus? Maybe, but there are good reasons to wait until then. “This is when the south pole of Enceladus will enter the southern summer, meaning more of it will be illuminated as the mission progresses,” said MacKenzie.
Although it was Cassini who unveiled its subterranean ocean, NASA Voyager images in the 1980s revealed that Enceladus was both very bright and devoid of craters; clues that it was covered in highly reflective ice and that its surface is constantly renewing itself. In short, Enceladus is geologically active – it’s hot and humid…it’s where life as we know it can exist.
Enceladus will always be a world of interest in the search for life beyond Earth. It’s only a matter of time before NASA visits it.
I wish you clear skies and big eyes.