(Before and after pictures showing the appearance of the island – Photo Credit: NASA/JPL-Caltech/Cornell)
Scientists have outlined their best explanations for a ‘magic island’ that has been discovered on Saturn’s moon, Titan. The bright, mysterious geologic object appeared and later disappeared in a location where one had not previously existed. NASA’s Cassini spacecraft captured a photo of the “island” during a flyby, but it had vanished by the time Cassini next passed by.
The bright splodge was spotted in Ligeia Mare, a sea of methane and ethane found at Titan’s north pole. It was visible in pictures from a Cassini flyby on the 10th July 2013 however the “island” is absent in photos taken on three previous flybys. By the time Cassini next passed Titan on 26th July, the feature had once again vanished and was not visible in two subsequent flybys.
To discover this geologic feature, the astronomers relied on a technique known as ‘flipping’. The Cassini spacecraft sent its photographs to the Jet Propulsion Laboratory for image processing. Once developed, a team of astronomers flipped between older Titan images and the newly processed pictures for any signs of change on the lunar surface.
Once spotted, the team began investigating the ‘island’ and now Jason Hofgartner, co-author of a new study on the island, and his team have released a new study which discloses the possible explanations.
“Magic Island is a colloquial term that we use within the team to refer to this. But we don’t actually think it’s an island,” Hofgartner explained.
“We have four different hypotheses that are all equally preferred. In no particular order they are: waves, rising bubbles, floating solids and suspended solids” he added.
Titan’s seasons change on over a longer time scale than Earth’s. At the time of discovery, the moon’s northern hemisphere was transitioning from spring to summer therefore the astronomers believe the strange feature may result from the moons changing seasons.
The four potential explanations for the island are as follows:
• Northern hemisphere winds on Titan may be forming waves on Ligeia Mare, and Cassini’s radar imaging system might have seen the waves as a kind of “ghost” island.
• Gases pushed to the surface of Ligeia Mare, from a subsea volcanic vent, may have risen to the surface as bubbles which appeared in the shape of an island.
• Sunken solids formed in the winter season could have become buoyant due to the onset of warmer temperatures during the late Titan spring.
• Ligeia Mare is known to have suspended solids, a frozen mixture of methane and ethane, which are neither sunken nor floating, but act like silt in a terrestrial delta.
“This discovery tells us that the liquids in Titan’s northern hemisphere are not simply stagnant and unchanging, but rather that changes do occur,” said Jason Hofgartner “We don’t know precisely what caused this ‘magic island’ to appear, but we’d like to study it further.”
The authors of the latest study hope that future observations by Cassini might yield more evidence of the phenomenon, and if they do, there could be a chance to distinguish between the different possible causes.
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