Saturn moon Enceladus to support life


NASA’s robotic Cassini spacecraft discovered a precondition for the existence of life forms on the icy world of Enceladus.

Enceladus was discovered in 1789 by William Herschel. Very little was known about it. It is Saturn’s sixth largest moon. Enceladus was discovered in 1789 by William Herschel. After its discovery very little was known about it until the two spacecraft passed nearby in the early 1980s. It is among the most scientifically compelling bodies in our solar system, which is 157 miles away in mean radius. Enceladus orbits Saturn at a distance of 148,000 miles/ 238,000 km, falling between the orbits of Mimas and Tethys, two other closest moons of Saturn.

In 2005, the Cassini spacecraft started its multiple close flybys of Enceladus, revealing its surface and environment in greater detail. The Cassini-Huygens mission was carried out in cooperation between NASA, the European Space Agency, and the Italian Space Agency. In particular, Cassini discovered water-rich plumes venting from the South Polar Region. It keeps the same face towards the planet because it is tidally locked with Saturn and is trapped in an orbital resonance. Its resonance with Dione excites its orbital eccentricity, heating the interior and damping the tidal forces. This phenomenon results in driving the geological activity.

According to studies conducted by NASA, it has a sub-surface liquid water ocean between its rocky core and icy crust. Due to the presence of global water ocean and other discoveries like plume venting from its the South Pole, hydrocarbons in plumes, hydrothermal vents on the seafloor, and the presence of gasses, there is a possibility that Saturn’s moon is habitable beyond Earth’s habitable zone.

Dr. Caitriona Jackman, a space environment lecturer, from the University of Southampton said that the discovery that was announced on Wednesday is that Enceladus plumes have molecular hydrogen.

“Hydrogen is considered to be a major energy source that is capable of supporting life, most probably microbes,” Jackman said.

The NASA’s robotic space probe, dubbed Cassini is in the mission, orbiting around Saturn since 2004. In 2015, it was discovered by researchers that the magnitude of the moon moves unsteadily from side to side. Saturn can only be accounted for it if its outer icy shell is not frozen solid as a whole to its interior, which means that an ocean is present inside.

This interference implies that plumes venting from the South Pole are fed by this huge liquid water reservoir. According to measurements, the findings suggested that large sea is present about 6 miles deep beneath the southern polar region and below 19 – 25 miles thick icy shell.

Due to the icy shell, its surface reflects sunlight like freshly fallen snow; Enceladus is said to reflect almost 100 percent of the sunlight that strikes it. Due to this reason, its surface temperature is extremely cold to about -201 degrees C.

Christopher Glein, a member of the Cassini team at the Southwest Research Institute said, “We think that hydrothermal reaction between liquid water and rock is making the hydrogen.” The hydrothermal vents emitting hydrogen-rich water in the ocean are an indication that life can survive on Saturn’s moon.

According to Woods Hole Oceanographic Institution senior scientist and geochemist, Jeffrey Seewald, In the Enceladus ocean there exists a state of chemical disequilibria that represents a chemical energy source which is capable of supporting life.”

“We have discovered very encouraging signs that there is habitable environment on Enceladus, which is great because this discovery moves us one step closer to understanding Enceladus, but we’re not quite at the stage of determining whether life is present. It is possible that tidal process plays an important role in the happenings inside the icy crust, in the water world. There is still no evidence that any life exists there yet,” Glein added.

Enceladus displays almost five different types of terrain. These various terrains indicate that some major geological event has happened in the recent past which has caused its resurfacing. There all are related to the liquid interior of the moon, specifically including plans, fissures, corrugated terrains, and geysers. Besides these, Enceladus also has craters up to 22 miles in diameter in some areas while there are also places with no craters.

In the region towards the South Pole, there are unique house-sized ice boulders and tectonic patterns are carved on the surface. This area of Enceladus is almost free of impact craters.

Scientists call the fractures deep in the crust as “tiger stripes”. These tiger stripes supply the cloud of water vapors and ice particles that extend from there into space. Some hotspots near these crevasses also release jets. With the presence of global ocean, unique terrain and chemistry, Enceladus has become a promising lead in the research field around the world where life could exist.

Previously Enceladus seemed and was considered just a frozen moon snowball in the outer solar system. The presence of covered ocean was revealed by the plumes. Glein and other researchers analyzed the data collected by the NASA’s spacecraft. They found significant amount of hydrogen and carbon dioxide. The robotic space probe detected hydrogen at the center of these new insights in an icy plume coming out from cracks in Enceladus’ surface.

Cassini is scheduled to end its mission with a spectacular descent into Saturn later this year. NASA has plans to visit Europa in the next decade. Europa is the sixth largest moon in the Solar System.  It is among the smallest of the four Galilean moons orbiting around Jupiter and the sixth closest to the planet.

Still, after the finding that Enceladus has preconditions to support life, there much more to work and find about other aspects of research. To learn about the distant moon in detail plenty of work is required to be done by geophysicists, geochemists, and biologists along the way.

This study has raised a lot of tantalizing queries. There is need to figure out that what is really happening beneath the Enceladus. Amazingly it might have some form of life, intriguing the icy curtain and discovery of methanogenesis needs time to conclude the findings.