NASA Probe to Help Determine if Pluto Moon Charon Once Had Subsurface Ocean


Due to the distance between Earth and Pluto, collecting scientific data on Pluto and its moons has been challenging. Scientists are hoping that in July, 2015, when NASA’s New Horizons probe flies by Pluto, it will be able to provide strong images of Charon, Pluto’s largest moon, in order to determine whether cracks in the surface are visible. Detecting and analyzing those cracks will be instrumental in determining whether Pluto’s temperature was ever high enough to enable it to maintain an ocean beneath its surface.

Although researchers believe that the temperature on the surface of Pluto and its moons is -380 degrees Fahrenheit (-229 degrees below zero Celsius), it is considered possible for liquid water to exist under the surface of Charon. Other bodies in the universe also may contain large amounts of ice-covered water, including Enceladus, Saturn’s moon, and Europa, Jupiter’s moon. It is thought that the interior of these planets are warm enough that despite their icy surfaces, liquid water should exist, especially when adding in the influence of tides.

Pluto and Charon are locked tidally, so that if there was an ocean on Charon, it would most likely be frozen. However, large tides occurring in Charon’s past would have caused a certain crack pattern in the ice of its surface, providing evidence of a long-ago ocean. According to NASA on Friday, if results from New Horizons correspond to one of the models developed by their scientists, they will be able to determine whether Charon could have, due to its high eccentricity, supported an ocean beneath its surface. In astronomy, eccentricity measures the deviation of a particular orbit from being circular. A perfectly circular orbit is assigned an eccentricity of zero.  The higher the number, the more elliptical the orbit is. Pluto has one of the most eccentric orbits in Earth’s solar system.

NASA’s Alyssa Rhoden is lead author of the study, which was published in the journal Icarus and is available from Science Direct. Multiple models of Charon have been created which use the make-up of its interior and how readily it can be deformed, measurements of its surface ice thickness, and the evolution of its orbit in order to determine how those factors would have worked together to create cracks on the surface of Charon. Scientists hope that any data gleaned by New Horizons will allow them to correspond one of these models with the actual fissures created on the moon, leading them to determine which of the models is most accurate.

The question of whether or not Charon once supported a subsurface ocean is germane to the question of whether or not other moons could have once supported life. Water in liquid form is vital for life to form, but a source of energy and a perfect mix of chemicals are also required, leaving the question of whether Charon, Enceladus and Europa could have supported life at one time a complex issue to determine. NASA hopes that the New Horizons probe will provide a glimpse into Charon’s ancient past when it soars by Pluto in July 2015.

By Jennifer Pfalz


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