It is a small world, only 310 miles in diameter, and until recently was considered one of the least interesting moons in the solar system. But Enceladus, one of 146 moons orbiting Saturn, has become a hot astronomical attraction; Scientists have discovered that it offers one of the best odds of finding life on another world in our solar system.
The European Space Agency (Esa) announced that it has begun planning a mission to take a robotic probe billions of kilometers into space to conduct research.
It will be a project that generates extraordinary taxes. In addition to the enormous distance the probe would have to travel, it would also need large reserves of fuel to enter orbit around Enceladus and land on the icy surface.
However, the prospect of studying the small moon is quite tempting for astronomers, who have discovered that Enceladus, first observed by William Herschel in 1789, has geysers that regularly erupt from its surface and spray water into space. Even more surprising, these fumes contain complex organic compounds such as propane and ethane.
“There are three key ingredients thought to be necessary for life to emerge on Enceladus,” said astronomer Prof Michele Dougherty from Imperial College London. “It has liquid water, organic matter and a heat source. “This combination makes it my favorite moon in the entire solar system.”
This view is shared by Esa, who recently tasked a trip to a moon of Jupiter or Saturn as the next target for a major scientific effort. Such a project is expected to deliver a “transformational scientific payoff,” according to a panel of expert scientists examining three main targets: Jupiter’s icy moon Europa; Saturn’s hydrocarbon-rich moon Titan; and Enceladus. All have subsurface oceans that hold the promise of sustaining alien life forms and could become prime targets for scientific study.
After months of consideration, the panel reported a few weeks ago that Enceladus, the final target on this interplanetary list, should be prioritized over other targets. By 2040, a mission should be launched with the aim of either landing on the moon or flying past geysers that spew water and carbon chemicals from its surface into space. The panel added that preferably both targets should be attempted.
Chairing the panel was astrobiologist Dr. from Instituto Superior Técnico. “The mission will deliver a tremendous scientific return and will lay the foundation for the successful detection of biosignatures on icy moons,” said Zita Martins.
But as Dougherty noted last week, achieving such goals won’t be easy. “It’s one thing to put a probe into orbit around a large moon or planet that has a strong gravitational field that could slow an incoming spacecraft. But Enceladus is small and has weak gravity, meaning it doesn’t require too much fuel to slow it down so it doesn’t hurtle past its target and into deep space.” This will be a difficult issue for those designing the mission.”
Dougherty’s particular interest in Enceladus stems from his role as principal investigator of the magnetometer flown on the Cassini mission, which studied Saturn and its moons between 2004 and 2017.
“At one point Cassini passed close to Enceladus, and our instrument showed that Saturn’s magnetic field was drifting around the moon in a way that suggested the little moon had an atmosphere,” said Dougherty.
Cassini’s managers agreed to direct the probe to examine it more closely, and in July 2005 the spacecraft passed over the lunar surface at an altitude of 173 km and detected significant amounts of water vapor. “It was great,” Dougherty recalls.
Subsequent scans produced even greater miracles. Huge water geysers have been photographed gushing from geological fault lines at the south pole. The only body in the solar system other than Earth that has liquid water on its surface has been discovered. Organic materials were eventually discovered in these clouds, transforming Enceladus from a small, insignificant moon into a world that would now trigger the expenditure of billions of euros and decades of effort by European astronomers and space engineers.
Is there life on other moons?
Titan
Titan, another moon of Saturn and one of the largest moons in the solar system, has hydrocarbon lakes and seas; river channels; large sand dunes; and indicates that it has an underground ocean that could host primitive life. It is also exceptionally cold.
Anthem
The red planet was a warm, watery world 4 billion years ago, with ideal conditions for life to emerge. However, Mars later lost its magnetic field, water and atmosphere and was exposed to intense ultraviolet radiation. Life would have had a hard time surviving on the surface, but they may have survived as microbes underground.
Europe
Europa, one of Jupiter’s main moons, is completely covered in ice and has the smoothest surface of any known solid body in the Solar System. Beneath its surface is an ocean of water that scientists believe may harbor extraterrestrial life, most likely consisting of primitive bacteria-like entities.