Titan: Clue to 'Magic Island' mystery on Saturn moon

The bright feature shown in the image was spotted in images from July last year, but a few days later it had vanished

Scientists have outlined their best explanations for a mysterious feature dubbed the "magic island", which has been spotted on Saturn's moon Titan.

The Cassini spacecraft captured the "island" during a flyby, but it had vanished by the time of the next pass.

The bright splodge is seen in Ligeia Mare, one of the seas of methane and ethane found at Titan's north pole.

Icebergs, waves and gas bubbling up from the sea bed are all possibilities, the scientists say.

The study by an international team has been published in the journal Nature Geoscience.

Ligeia Mare is the second largest body of liquid on the saturnian moon

Saturn's largest moon shares much in common with Earth, such as a substantial atmosphere and a seasonal cycle. Wind and rain shape the surface to form river channels, seas, dunes and shorelines.

Titan's mountains and dune fields are made of ice, rather than rock or sand, and liquid hydrocarbons take many of the roles played by water on Earth.

The seas and lakes peppering the moon's north polar region are filled with methane and ethane. These are gases on Earth, but at typical Titan temperatures of -180C, they exist in a liquid state.

Titan, seen here with Tethys in the background, is shrouded in an orange haze of organic chemicals

• Titan is Saturn's largest moon and the second biggest in the Solar System
• It is the only moon in the Solar System with clouds and a substantial atmosphere
• Wind and rain create similar features to those found on Earth, such as dunes, lakes and rivers
• But on Titan it rains liquid methane, filling the rivers, lakes and seas with hydrocarbons

The bright feature was spotted in pictures from a Cassini flyby of Titan on 10 July 2013. The "island" is absent in imagery of Ligeia Mare taken on three previous flybys.

By the time of the next pass of Titan, on 26 July, the feature had vanished, and was not visible in two subsequent flybys.

"'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," co-author Jason Hofgartner told reporters.

The feature appears and disappears too quickly to be a volcanic islet. So the team were left with a handful of potential explanations.

Titan's lakes and seas are thought to be filled with a mixture of liquid methane and ethane

Mr Hofgartner, who is based at Cornell University in New York, 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."

Titan operates on a 30-year seasonal cycle, and the moon's northern region is expected to become a more dynamic place as Titan approaches its summer solstice in May 2017.

"Right now, Titan is basically half way between the vernal equinox (August 2009) - at the beginning of spring - and the summer solstice, the start of summer. It's roughly equivalent to what we would consider the beginning of May," said Mr Hofgartner.

"As Titan approaches its summer, more of the Sun's energy is being deposited in the northern hemisphere."

Winds will get stronger, causing an increase in waves, which are one potential explanation for the "magic island". Researchers have already seen possible evidence for small waves on another Titan sea.