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Earlier this week scientists were left baffled by a huge feature that surfaced in the seas of Titan that measured a staggering 100 square miles (260sq km) - the size of Washington DC or the city of Birmingham in the UK.

And in the latest speculation a number of theories have been considered including a giant iceberg and a huge field of bubbles.

Speaking to MailOnline, two scientists explained their thoughts on what it might have been and that they hope to learn more upon repeated observations early next year.

In this series of images from the Cassini spacecraft the giant object 100 square miles (260 square kilometres) in size is seen rising out of one of Titan's largest seas before disappearing again. In the latest image on the right the object still seems to be partially submerged beneath the surface 

In July 2013 the giant feature was seen surfacing from under the liquid before partially disappearing again in August this year.

Regarding the iceberg theory one scientist explains how, if it's the correct assumption, they might differ to icebergs on Earth.

'For a bit of background, on Earth it's quite a simple situation because ice floats in water,' Jason Hofgartner, a graduate student at Cornell University who works on the Cassini Radar Science Team, tells MailOnline.

'On Titan it's more complicated because you have a methane and ethane mixture, we think, and there's nitrogen from the atmosphere that also gets dissolved.

'So when you freeze it, it undergoes complicated composition changes.

'Whether you can get icebergs that can float is a matter for debate, but it's possible.

'When it warms those icebergs could switch from sinking to floating.'

Hofgartner explains how the northern hemisphere, where the iceberg was spotted, is currently transitioning from spring time to summer.

This process might be responsible for warming the sub-surface icebergs, which then caused them to rise from the seabed.

Other processes like currents in the sea could also be dislodging such features.

Another theory is that it is a bubble, although not necessarily a giant bubble across the whole feature.

Hofgartner says it could be a series of smaller bubbles spread over the huge area, each perhaps just centimetres in size.

The cause of these bubbles could be vents, undersea volcanoes or seasonal changes.

One theory that can be ruled out, however, is that this is some sort of giant non-ice land mass that has risen from the depths.

This is because the radar system on Cassini can penetrate into the liquid so it would have spotted such a land mass.

'If this was a land mass or mud flat under the sea, we should have seen it in earlier images because the radar would have penetrated,' he explains.

A comparison image from 26 April 2007 (left) shows how no similar feature was previously spotted in the region of interest. The feature was spotted by Nasa's Cassini spacecraft, which is currently in orbit around the Saturnian system. On the right is an image of Titan in orbit around Saturn

Another feature of the images is that the object appears to be fading.

'I don't know if that's anything to do with what's under the liquid; we see it's decreased in brightness an extending.

'So what could be happening is it's spreading out and becoming less concentrated in one area, and spreading into a larger area.'

The feature is certainly rare, although it's possible that more may be spotted in future.

This specific area will be imaged by radar again early in 2015, and exactly what state the feature is in will surely be of huge interest.

One of Nasa's future proposals to Titan is for a boat to sail the seas, but Hofgartner says features like this would not necessarily be a threat to such a mission.

'Perhaps the boat could help us nail down what is happening here,' he says.

This is an artist's impression of the Titan Mare Explorer (TiME) capsule, a proposed mission to perform the first direct inspection of an ocean environment beyond Earth by landing in, and floating on, a methane-ethane sea on Saturn's largest moon: Titan

Speaking to MailOnline Professor of Planetary Plasma Physics Emma Bunce from the University of Leicester, who also works on the Cassini mission, agreed that it may have been some sort of iceberg akin to something we see on Earth.

'It could be something floating that sunk and came back to the surface,' she says.

'I was thinking almost like an iceberg, similar to something in Earth's oceans.'

But she doesn't rule out the possibility of it being some sort of giant bubble, or even surface waves.

She goes on to explain that the feature may have arisen due to the change in season at Saturn.

The first image in 2007 was taken 'around Saturn equinox [when the sun is above the equator], and then the latest image is now heading towards northern summer solstice on Saturn.

'That's sort of an ongoing theme for a lot of the Cassini results; a lot of things depend on the season at Saturn as it moves in orbit.

'Because this lake itself is actually near to Titan's northern pole, perhaps it is something to do with illumination conditions.'

The feature was spotted in Ligeia Mare (shown), one of the largest seas on Titan, and was observed by Cassini's radar experiment. Several theories currently exist including surface waves, rising bubbles, floating solids, solids suspended just below the surface or 'something more exotic' according to Nasa

The feature was spotted by Nasa's Cassini spacecraft, which is currently in orbit around the Saturnian system.

It was spotted in Ligeia Mare, one of the largest seas on Titan, and was observed by Cassini's radar instrument.

In images from 10 July 2013 to 21 August 2014 the feature is shown rising and then falling below the surface.

A comparison image from 26 April 2007 shows how no similar feature was previously spotted in that region. 

The mysterious feature appears bright in the radar images, suggesting it has a somewhat similar composition to the land nearby in the image.

This supports one theory that it may be a solid structure that surfaced from under the liquid before sinking again for an unknown reason.

The dark area in the image is the liquid hydrocarbon sea on Titan's surface, while the bright area to the right is land.

Scientists on the radar team are confident that the feature is not an artifact - or flaw - in their data.

They have also ruled out the possibility of it being due to evaporation, as the nearby shoreline has not changed much.

Several theories currently exist including surface waves, rising bubbles, floating solids, solids suspended just below the surface or 'something more exotic' according to Nasa. 

The appearance of the feature may also be due to changing seasons on Titan, with summer drawing near in the moon's northern hemisphere.

Monitoring these changes is a major goal of Cassini's current extended mission.

'Science loves a mystery, and with this enigmatic feature, we have a thrilling example of ongoing change on Titan,' said Dr Stephen Wall, the deputy team lead of Cassini's radar team, based at Nasa's Jet Propulsion Laboratory in Pasadena, California.

'We're hopeful that we'll be able to continue watching the changes unfold and gain insights about what's going on in that alien sea.'

It has been a decade since Cassini entered orbit around Saturn (illustration shown). In June the Cassini mission celebrated 10 years of exploring the planet, its rings and moons. It arrived for a four-year mission but has since been continuously extended, although it will almost certainly end in 2017