In May 2015, NASA announced a mission to Europa Clipper, the icy moon of Jupiter. The spacecraft will carry a probe that will orbit around Jupiter, allowing it to fly by Europa dozens of times and gather data on the liquid ocean believed to exist under its icy surface.
What is the significance of this mission?
Water is essential to life on earth. Thus, researcher looking for life elsewhere in the solar system are searching for water on other planets.
Of 67 moons of Jupiter, Europa is the fourth-largest moon and is roughly the size of Earth’s moon. It was discovered by Galileo in 1610 and is named after a figure from Greek mythology.
Europa has an enormous ocean beneath its icy crust shields, despite the moon’s great distance from the sun. Its outer surface is made up of ultra-cold ice: -260°F at the equator, and -370°F at the poles.
As Europa travels around Jupiter, the massive planet bends and flexes the satellite, generating interior heat that keeps its water from freezing completely. When the Voyager spacecraft (by NASA) flew by Europa in 1979, it revealed a cracked, icy surface with very few craters — indicating that the ice was continually being recycled, a piece of evidence that supports the idea of liquid underneath.
In 1997, when the Galileo probe flew by Europa, it found that the moon had a magnetic field, likely caused by the circulation of a saltwater ocean. Subsequent work has indicated that in some places, this subsurface ocean is actually leaking through the ice, and calculations indicate the ocean could have two to three times as much total water as all of Earth’s oceans.
Also NASA’s Hubble Space Telescope discovered a third region where scientists could search for the ingredients for life: geysers of water vapor erupting from Europa’s southern hemisphere, possibly allowing a flyby probe to sample the moon’s subsurface sea from afar.
There is also unique characteristic of Europa over other Icy moons in Solar system. Its ocean is believed to be in direct contact with its rocky interior, where conditions could be similar to those on Earth’s biologically rich sea floor. The hydrothermal zones, where water and rock interact at high temperatures are known to be rich with life, powered by energy and nutrients that result from reactions between the seawater and the warm, rocky ocean floor.
As the other important component essential for life are carbon and nitrogen. Thus Scientist also looked for if such organics can be found over Europa. The researchers found that there is a constant bombardment of high-energy ions (from Jupiter’s magnetic field) and sulfur (from volcanic activity on another of Jupiter’s moons over Europa’s surface. Certain salts and hydrogen peroxide are also believed to be on the surface. If all of these chemicals could make their way through the ice into a liquid ocean, they could lead to the sorts of chemical reactions in the water that would provide food for microbial life forms.
All above factor makes the Europa mission significant.
About the Mission?
The mission planned in 2020 by NASA, is expected to reveal if Europa is habitable and will not if it has life — largely because a “life detector,” doesn’t currently exist. Scientists are not certain what life would look like on another world, and thus don’t know what all to be measured to test for it.
Variety of instruments will be fitted on Europa Clipper.
A magnetometer will be placed to calculate the depth and saltiness of its ocean.
Radar and a heat detector will also be there to reveal the subsurface structure of the ice, showing how it might turn over throughout time, perhaps providing chemical energy and organics to the ocean.
An ultraviolet spectrograph will search for plumes shooting out of the icy surface, allowing mission scientists to target them on subsequent flybys.
The dust and gases contained within these plumes might originate on the ocean bottom, so sampling them with the craft’s mass spectrometer could indicate the presence of hydrothermal vents on the seafloor.
An infrared spectrometer will reveal the composition of the brown streaks on Europa’s surface that likely leak out of the ocean.
High-resolution cameras will also be fitted to map Europa’s surface for a potential follow-up mission in the future. There is no plan to land a probe on Europa.
About other Icy moons in the Solar system:
In 2005, Cassini’s multiple instruments discovered that Enceladus, an icy moon of Saturn is gushing water vapor geysers out to a distance of three times its radius.
The subsurface oceans are also suspected to exist on Jupiter’s moons Ganymede and Callisto, Saturn’s moon Titan, and a number of dwarf planets scattered throughout the solar system.