Water+and+Life+on+the+Icy+Moons+of+the+Solar+System

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=** Introduction **=

Life as we know it could not exist without the presence of liquid water. For decades, scientists have speculated about oceans in other worlds and about the life forms that could inhabit them. There has been particular interest on the icy moons of the Jovian planets because some might hide entire oceans underneath their icy cover. Past missions have flown by and have revealed more details about a few of these mysterious worlds. Astronomers and other scientists have analyzed the data and made speculations about the habitability of such places. Further research needs to be conducted in order to determine if any of the moons contains all the ingredient, apart from water, for life as we know it to exist. Future NASA and ESA missions aim to explore and answer more questions about the icy Jovian moons and about the possibility of life forms inhabiting them.

=** Icy Moons **=

Even though the Jovian moons are far from the Sun’s habitable zone, the region around with the right temperature for water to remain on a liquid state, it is possible that tidal interactions with their large parent planet could provide enough heat for water to be liquid just underneath the icy crust. The moons suspected to have oceans are Jupiter’s Galilean moons Europa and Ganymede, Saturn’s moons Callisto, Enceladus, Titan and Mimas, and Neptune’s moon Triton [2].

** Europa **


Jupiter’s moon Europa was observed from Earth more than three decades ago, pictures showed that its surface was made up of mostly ice [13]. In 2003, the Galileo orbiter, part of NASA’ s Galileo Mission, made many flybys around Europa. This spacecraft took measurements and close up pictures of Europa’s surface, pictures revealed strange pits and domes, telling scientists that some small pieces of the icy crust might be moving around, as if a liquid were present [5]. This could also mean that the icy crust is not thicker than a few meters at certain places [7]. Additional measurements revealed that Europa is a differentiated body, possibly with solid core; that interactions with Jupiter produced an induced magnetic field; and that the outer shell of Europa is denser than ice, which could mean that it has a high liquid content. In 2013, NASA’s [|Hubble Space Telescope] imaged the surroundings of Europa and discovered liquid water plumes erupting from the moon’s surface [2]. These plumes rise about 200 km from Europa’s surface [1], showing that the moon’s ocean might operate in a similar fashion than that of Enceladus [11]. These plumes also tell scientists that Europa might have active cryovolcanism [9].



** Enceladus **
Europa is not the only moon that has had missions fly close-by. Saturn’s moon [|Enceladus] has also have some close-up attention. The Cassini Mission, whose primary purpose was to investigate Saturn, made several flybys around Enceladus. The mission measured Enceladus magnitude and noticed that it wobbles as it orbits Saturn; this only makes sense with computer models if the outer shell is not all frozen solid. The spacecraft also took pictures that show water plumes being ejected from the icy surface [6]. "The shadows observed most likely indicate the precense of “plumes of water vapor”, say [|William Sparks] of the Space Telescope Science Institute and colleagues. It is still unknown what pushes the plumes into space, but the plumes confirm the pretense of liquid water underneath the icy surface. Cassini scientists also confirm that the mission detected the presence of hydrogen gas in the water plumes coming out of the south pole of Enceladus, this gas seems to be produced by hydrothermal activity on the sea floor [8].n The data helped astronomers create models of the interior of Enceladus. Computer models agree that Enceladus hits a global ocean, but the thickness of the icy layer and other internal layers remains unknown [8].



** Other Moons **
The other moons mentioned, Ganymede, [|Callisto], Titan, Mimas and [|Triton], have not been analyzed in such depth as Europa and Enceladus, but ground observations have revealed that they are very similar in composition to Europa and Enceladus and thus could also hold large oceans underneath their icy crust [2].

=** Data Analysis **=

“The history of the oceans is the history of life [2]”. Life as we know it originated in the oceans. Finding out that large oceans exists in other parts of the Solar System means that life is able to exists in other parts of the Solar System [7][8][12]. The presence of Hydrogen gas is relevant because it is a form of “chemical energy that life can feed on”, this gas plus the presence of water make up the perfect stage for life to exist [2]. It has been suggested that many different sorts of life form could exist underneath the icy core of one or more Jovian Moons. From small unicellular organisms, to fish and other animals [8]. "This is the closet we've come, so far, to identifying a place with some of the ingredients needed for a habitable environment,” said [|Thomas Zurbuchen], associate administrator for NASA's Science Mission Directorate at Headquarters in Washington. [2] NASA’s astrobiology department has looked into the different environments that organisms can survive in and their observations agree that Europa’s ocean will not likely have harsher environments than some on Earth, in which extreme can organisms exist [12].

=** Further Research **=

Much research is needed in other to make definite conclusions about Europa and other icy moons. Questions like how have these moons evolved through time? How do tectonic surface features constrain the thermal history and current heating rate of all of them? [13] And can craters tell us anything? Still remain unanswered. The current findings generate considerable excitement among scientists and politicians. It is important to understand that these findings make scientists very Europa, Enceladus and the other icy moons will be further investigated in the future. Europa will be the first one, this decision was made because the it is thought that it’s icy crust might not be thicker than a few meters in places, allowing the possibility of a lander drilling trough the ice to look at the liquid ocean [7]. Scientists may use the infrared vision of NASA’s James Webb Space Telescope, which is scheduled to launch in 2018, to confirm venting or plume activity on Europa. NASA also is formulating a mission to Europa with a payload that could confirm the presence of plumes and study them from close range during multiple flybys. [1]

=** Future Missions **=

There are two missions dedicated to the icy moons by the two world largest space agencies, ESA and NASA.

Europa Clipper
// Europa Clipper, // one of NASA’s most recent orbiter missions, will be launched in early 2020; its goal is to “explore the ability of Jupiter’s icy moon” [3]. This mission plans to do many flybys around Europa rather than orbit the moon in the hopes to avoid high levels of radiation coming from Jupiter. Flying trough the plumes of Europa, the Europa Clipper will be able to analyze the plumes and provide information that scientists could use to find their source and more information about their composition and the ocean they come from This mission was highly criticized by politicians for not having a lander, which could drill trough Europa’s icy crust and take a close up look at the ocean [3].

JUICE
ESA’s mission, scheduled to launch two years later, will be dedicated to look at the habitability of Europa and other Jupiter moons, this mission is called JUpiter ICy Moons Explorer (JUICE) and will reach the Jupiter system by 2029. This mission will not only look at Europa but also at the other icy moons of the Jupiter system. By understanding more about how the Jupiter system works as a whole, ESA scientists expected to find out how the tidal interactions affect each moon and how those interactions affect the oceans and what could this mean for life forms that could exist there [4].

=** Conclusion **=

The story of oceans is the story of life. Life as we know it has its origins in the oceans and the oceans allow our world to be inhabited, they provide a global circulation and source of energy for most life forms. Understanding the history and characteristics of the oceans in other worlds will help us understand if life could exist in any of those places. Investigation of the animals living in similar environments on Earth could help us understand what to expect to find in Europa’s ocean and other moons’ oceans. Current missions pave way for future exploration, ultimately perhaps including landing operations. Such landings could confirm the presence of life or help scientists understand what is missing in such places for life to exist.

= Cited References =

[1] Potter S. NASA’s Hubble Spots Possible Water Plumes Erupting on Jupiter’s Moon Europa [Internet]; 2016 Sept 16 [cited 2017, June 14]. Available from __https://www.nasa.gov/press-release/nasa-s-hubble-spots-possible-water-plumes-erupting-on-jupiters-moon-europa__

[2] NASA/JPL Caltech. NASA Missions provide New Insights into Ocean Worlds; [cited 2017 June 14]. Available from __https://www.nasa.gov/press-release/nasa-missions-provide-new-insights-into-ocean-worlds-in-our-solar-system__

[3] Europa Clipper. [Internet];[cited 2017 June 14]. Available from __https://www.jpl.nasa.gov/missions/europa-clipper/__

[4] Bauer M. ESA’s Jupiter Mission [Internet]; 2017 March 15 [cited 2017 June 14]. Available from __http://sci.esa.int/juice/58887-esa-s-jupiter-mission-moves-off-the-drawing-board/__

__ [5] __ Moore J. Impact Features on Europa: Results of the Galileo Europa Mission (GEM). Icarus. 2011; 151.

[6] Waite J, Glein C, Perryman R, Teolis B, Magee B, et al. Cassini finds molecular hydrogen in the Enceladus plume: evidence for hydrothermal processes. Science Journal. 2017.

[7] Werner D. Ambition Europa. Aerospace America. 2016 June 16;54(6)22-7.

[8] Lunine J. Ocean Worlds exploration. Acta Austronautica. 2017 February; 131(1)123-30.

[9] Sparks W, Schmidt B, et al. Active cryovolcanism in Europa. Astrophysical Journal Letters. 2017 April. 839(2); L18.

[10] Talbert T. NASA receives science report on Europa lander concept. NASA [internet]; 2017 Feb 8 [cited 2017 June 20]. Available from https://www.nasa.gov/feature/nasa-receives-science-report-on-europa-lander-concept

[11] Roth L, Saur J, Retherford K, et al. Transient water vapor at Europa’s south pole. Science Journal. 2014 Jan. 343(6167); 171-74.

[12] spaceX.com/dragon

[13] Greeley R, Sullivan R, et al. Europa: initial Galileo geological observations. ScienceDirect. 1998 Sept. 135(1); 4-24.

[14] Anderson J, Lau E, Sjorgen W, et all. Europa’s differentiated internal structure: inferences from two encounters. Sciene. 2014 March. 198(1); 145-62.