Thursday, April 7, 2016

Mission to Europa

An image of Europa taken
by Galileo in the late 1990's.
The brown streaks suggest the
presence of a sub-surface
ocean because contaminant
(claimed to include sea salt)
have mixed with the icy surface
to create the "dirty ice."
The Galileo mission, launched in 1989, revealed possible evidence of salt water below the surface of Europa, one of Jupiter’s moons. What Galileo discovered on Europa are bumpy features called chaos terrains. Analysis suggests that these features are formed from a heat exchange between Europa’s icy shell and an underlying ocean. This could provide a model for transferring nutrients and energy between the surface and the inferred ocean. While it was running out of fuel, Galileo was intentionally sent into Jupiter to be destroyed, in case leaving it in orbit would lead to it crashing into Europa and contaminating any potential life.

The Galileo mission piqued scientists’ curiosity about this moon, and a mission to Europa is expected to launch in the 2020’s. This mission, the Europa Clipper, will perform 45 flybys at various altitudes, from 1700 miles to 16 miles above the surface. Its goal is to take high-resolution pictures of the surface to determine its composition, and use an ice-penetrating radar to search for sub-surface waters. A thermal emission imaging system will survey the surface in search of any recent eruptions of warmer water, and other instruments will search for evidence of water and tiny particles in the moon’s atmosphere. This flyby approach will obviate the need to drill through layers of ice to find possible signs of life.

Why is drilling currently not an ideal approach? It is not definite that there is an ocean below the surface. It is possible that drilling before fully understanding Europa will be a waste of time, resources, and money. Also, the surface of the moon is exposed to extreme radiation from Jupiter’s radiation belts. A drilling machine or spacecraft will need a vast amount of radiation protection, which will make the craft heavy and thus expensive to transport. The flyby approach will decrease the amount of protection needed because the Europa Clipper will only be close to Jupiter during a small portion of its orbit.

On the other hand, if the Europa Clipper discovers strong evidence that suggests Europa has a sub-surface ocean that may be habitable for people or other lifeforms, a drill will be necessary to reach the habitable area. The amount of radiation on the surface is enough to cause severe illness or death after a single day’s exposure, but the thick, icy crust is thought to be able to shield the ocean from the radiation on the surface. While the Europa Clipper is not designed to search for life, a future mission would need to be designed to determine if Europa is already inhabited. It is uncertain now whether Europa is suitable to house life, but the Europa Clipper mission hopes to reveal if the ability is present.