Astronomers look for life beneath the surface of Saturn’s moon

Summary

Astronomers at the Royal Observatory of Belgium have discovered that one of Saturn’s moons may have a liquid ocean that could potentially harbour alien life

Is there life on… Dione?

It is the riddle that has puzzled us Earthlings for eons: is there life on other worlds or are we alone in the universe? An answer may have been found by star gazers in Brussels.

In September, astronomers at the Royal Observatory of Belgium discovered that one of Saturn’s 62 moons may have an ocean. As water is usually a pre-condition for life, it could mean that Dione, the planet’s fourth-largest satellite, harbours alien life forms.

“Dione could host microbial life because its ocean is in the habitable zone,” explains Mikael Beuthe, the co-author of the observatory’s study on Dione. “Life is so resilient. We now find it in the deepest mines and the darkest oceans, in very improbable places on Earth. So if we find it in one place, it can be expected in others.”

Beuthe is one of 170 scientists at the observatory in the Ukkel municipality of Brussels who works on a variety of research projects, from astronomy and astrophysics to seismology and meteorology. Based in Brussels, Beuthe has the classic scientist’s scraggly hair and waves his hands enthusiastically as he explains how he figured out that Dione has a hidden sea.

An ocean of secrets

First, though, he introduces Dione on his computer: It is a beautiful, cratered ball of ice and rock, home to hemisphere-wide ice cliffs. Dione is twice as large as its sibling moon Enceladus, which had previously been shown to spurt massive jets of water vapour into space from enormous geysers. (Jupiter’s moon Europa plays a similar trick.)

But while Dione is currently quiet, research suggests that its surface shows signs of a more active past. Beuthe used data from Nasa’s Cassini-Huygens spacecraft mission. During the spacecraft’s gravity fly-bys, miniscule gravitational changes are used to measure shapes and sizes. “It’s a bit complicated,” he says, and not for the first time.

When we find life, it will be the biggest discovery since we proved that Earth is not at the centre of the universe

- Mikael Beuthe

“Deep space antennas on Earth measure how Cassini’s trajectory changes,” he continues. “It is very precise and uses the Doppler effect. And it can measure disturbances that are just millimetres per second in the change in velocity, out of a speed that is kilometres per second.”

The tiny data changes pointed to something denser under the surface of the ice that could only be a layer of water. “Water is 10% more dense than ice,” Beuthe explains. “You can see that when you put an ice cube in whisky, it floats.”

Beuthe’s study, which he co-wrote with Attilio Rivoldini and Antony Trinh for the journal Geophysical Research Letters, suggests a 100-kilometre thick shell of ice floating atop a 65-kilometre deep ocean, which in turn smothers a rocky core spanning approximately 70% of its total radius.

This is far from the only planetary research the observatory is engaged in. It is also helping develop radio technology for the ExoMars mission to search for evidence of life on Mars, which the European Space Agency and the Russian space agency Roscosmos have developed.

ExoMars’ Schiaparelli lander crashed on the Martian surface last month, an event that shocked the entire observatory. But Beuthe says the team is working on the second part of the ExoMars project, to land a rover on the Red Planet in 2020.

The never-ending quest

The Ukkel observatory is spread over a 12-hectare site and opened its doors in 1890. The instruments were transferred from the city’s original observatory, set up by the Dutch King William I in 1826, before Belgium even became an independent country.

Other activities include research into the ice-sheet mass balance and Earth’s geomagnetic field, taken from data collected at the Princess Elisabeth Antarctica research station. The seismology section, meanwhile, measures local ground motion to detect and study earthquakes – sometimes getting readings from a loud concert on the other side of the city.

The observatory is also the home of the Solar Influences Data Analysis Centre, the world data centre for the Sunspot Index. But many associate the observatory with the Tintin comic book The Shooting Star, which sees the hero visit the institution to view the eponymous meteor through one of the telescopes.

Most of the telescopes are no longer in use: Even the biggest one, a majestic metal and glass machine built in Sheffield in 1909, has long ago been surpassed by more sophisticated viewing devices.

The Dione finding is just one of the leads researchers have in their quest for alien life in the solar system. Beuthe warns that they are unlikely to find three-eyed, seven-armed green monsters.

“We are looking at water-based life forms that are microscopic, including microbes, bacteria or algae,” he says. “But when we find them, it will be the biggest discovery in astronomy since we proved that Earth is not at the centre of the universe. It would totally change our point of view of life.”

Photo courtesy Nasa