Pluto's moon Charon may be the "Hulk" of the solar system.
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New images from NASA's New Horizons show evidence the moon may have aggressively expanded and fractured its outer layer, pushed by the a frozen ancient subsurface ocean, according to NASA. The space agency compared the expansion to the same way that scientist Bruce Banner busted out of his shirt to become the Incredible Hulk.
Charon, which is tidally locked in orbit with Pluto, has cracks, bruises and colorful spots that have intrigued scientists since New Horizons made its flyby of the system on July 14, 2015. NASA scientists said Charon's outer layer is primarily water ice, which may have melted to create the subsurface ocean.
"But as Charon cooled over time, this ocean would have frozen and expanded (as happens when water freezes), lifting the outermost layers of the moon and producing the massive chasms we see today," a NASA blog post explained.
Charon is home to some incredible surface features, including canyon system stretching 1,000 miles across the face of the moon and measuring four times as long as the Grand Canyon and twice as deep in places, indicating a violent tectonic history.
New Horizons, a piano-sized probe, is now speeding through the Kuiper Belt, an area at the edge of earth's solar system as it continues to send back a trove of data from its Pluto flyby. New Horizons loses about a few watts of power each year, according to NASA, but is estimated to have as much as 20 years left in its life expectancy.