APOD: Mystery Feature Now Disappears in... (2016 Mar 07)

[APOD Robot]

Mystery Feature Now Disappears in Titan Lake

Explanation: What is that changing object in a cold hydrocarbon sea of Titan? Radar images from the robotic Cassini spacecraft orbiting Saturn have been recording the surface of the cloud-engulfed moon Titan for years. When imaging the flat -- and hence radar dark -- surface of the methane and ethane lake called Ligeia Mare, an object appeared in 2013 July just was not there in 2007. Subsequent observations in 2014 August found the object remained -- but had changed. In an image released last week, the mystery object seems to have disappeared in 2015 January. The featured false-color image shows how the 20-km long object has come, changed, and gone. Current origin speculative explanations include waves, bubbling foam and floating solids, but still no one is sure. Future observations, in particular Cassini's final close flyby of Titan in 2017 April, may either resolve the enigma or open up more speculation.

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[StarHopper]

Easy. Global warming. Now who wants to try & deny it's really happening?

[RocketRon]

NASA suggested a few years back that this could be seasonal floating "ice".
http://www.nasa.gov/mission_pages/cassi ... 08_prt.htm

What has not been so discussed (?) is how such a volume of hydrocarbons could have formed on Titan,
and why it would concentrate on Titan in particular ?
Bearing in mind the compostion of all the outer gas-giant planets.
Perhaps someone could point us towards those discussions, or remind of the pertinent points....

[neufer]

https://en.wikipedia.org/wiki/Loch_Ness_Monster

[stowaway]

An unusual cloud like the one over China.

[northstar371]

https://en.wikipedia.org/wiki/Loch_Ness_Monster

That is an interesting source there but obviously it's a hoax. This wasn't taken in Titan Lake. Do you have other links to the real one?

[alex_ag]

This radar image is incredibly bautiful. We can almost see the botton of the lake near the shore. It seems to be crystal clear on this image. Waow !

[Ron Davis]

One hypothesis would be changes in the level of the liquid in the lake, especially since the transient feature is collinear with a peninsula and therefore in an area that would be expected to be relatively shallow when the feature is immersed. Change in liquid level can be caused by seasonal changes or just by weather variability. Against that hypothesis is that other shorelines seem not to move correspondingly, so that area would have to be very shallow when immersed.

[Buddy]

I like the small circular shape top center. It looks like a crater remnant with a small peak.

[Coil_Smoke]

It's not 'Dirt' we are looking at. The island melted back into the liquid it solidified from. This seems pretty likely, I am a bit surprised it is not already on the list. Methane, Ethane ... Frozen or Liquid ? The real mystery is the origin of these so called "Fossil Fuels" ?

[neufer]

The island melted back into the liquid it solidified from.
This seems pretty likely, I am a bit surprised it is not already on the list.

• (Northern Winter) 2007 => (Northern Summer Solstice) 2017

<<Ligeia Mare is a lake in the north polar region of Titan, the planet Saturn's largest moon. It is the second largest known body of liquid on Titan, after Kraken Mare. Larger than Lake Superior on Earth, it is composed of nearly pure liquid methane. The shorelines of Ligeia Mare and other north polar lakes and maria have been stable over the period of observation by Cassini, in contrast to south polar Ontario Lacus, where there has been significant shoreline recession. However, transient phenomena have been observed including a 260 square kilometre feature dubbed "Magic Island" by Cassini scientists. The "Magic Island" area only appeared in 2014 and may be waves, bubbles or subsurface ice rising to the surface as the lake warms up during spring, or possibly silt like material suspended in the liquid hydrocarbon sea.>>

Ice may float on the lakes of Saturn's moon Titan
Charles Black, Founder of Sen, Jan 15, 2013, 0:00 UTC

<<Scientists previously assumed that, because of its density, solid methane would sink on liquid methane. However, they have constructed a new model that takes into account the atmosphere and which adds pockets of nitrogen gas in the ice blocks, and which also takes into account changes in temperature. The results found that winter ice will float in Titan's methane and ethane rich lakes and seas if the temperature is below the freezing point of methane (90.4 K). Provided the ice had 5% or more "[nitrogen] air"... then it would float. If the temperature falls by a few degrees the ice will sink because of the relative proportions of nitrogen gas in the liquid versus the solid. The paper suggests that where the temperature is close to the freezing point of methane there could be both floating and sinking ice – a hydrocarbon ice crust above the liquid and blocks of the ice on the bottom of the lake or sea.

"We now know it's possible to get methane-and-ethane-rich ice freezing over on Titan in thin blocks that congeal together as it gets colder - similar to what we see with Arctic sea ice at the onset of winter," said Jason Hofgartner, lead author of the research and a Natural Sciences and Engineering Research Council of Canada scholar at Cornell University. "We'll want to take these conditions into consideration if we ever decide to explore the Titan surface some day.">>

- See more at: http://sen.com/news/winter-ice-will-flo ... iPjpr.dpuf

[LouisDyer]

Looks exactly like the Sometimes Islands in Lake Travis outside Austin, TX. When the lake level drops enough, the islands join to become a peninsula connected to the shore. When lake levels rise enough, they disappear altogether. The rest of the shoreline doesn't change as much with varying lake levels because they are made up of close to vertical cliffs. Does the radar data provide absolute altitude measurements of the lake level?

[iblevine]

I notice there is a straight line in the upper left-hand corner of the photo. Is it an artifact in the photo? I think it's quite unusual to see a straight line, which seems to go on for miles, in nature. Any ideas as to what it might be?

[Fred the Cat]

The fractal appearance of the tributaries leading into the lake is surprisingly like that of Earth's water networks. Fractals must have more in common with geometry than chemistry.

But is "fractisity" a universal feature that is related to gravity or scale?

[Boomer12k]

I am wondering how much is Camera Related....2007 is very clear, the others not so...with maybe static...then in 2015 is clear again. It also, appears to be "lower", then "more full"... but is "full" in 2007.

I would like to see the "full size" lake images of the times mentioned...to see any other changes around the lake.

:---[===] *

[Guest]

I know that Titan is tidally locked to the planet, but there is some variation in the orbit. Given the size of the lake/sea, is it possible for the orbital variations or other surrounding moons to be enough to cause 'tides' in the lake/sea?

[bluebass]

Have we overlooked the perfectly circular feature at the top of the frame? We need a conspiracy theory or better, a reasonable discussion what that might be. Crater? Trampoline?

[neufer]

Have we overlooked the perfectly circular feature at the top of the frame? We need a conspiracy theory or better, a reasonable discussion what that might be. Crater?

Soggy bogs swallow craters on Titan
New Scientist, 18 October 2013

<<The other meteors in the solar system were so lucky. They landed on nice, hard rock like on Mars or Mercury, exploding on the surface and excavating deep craters. If I had followed their lead, I could have left my mark! But no, I headed straight for this orange haze-ball Titan and plopped down in the northern marshes. I was a mere splash in an icy puddle, and all evidence of my existence was erased.

So was the fate of many a meteorite that struck Saturn’s largest moon, according to a new analysis of Titan’s topography. The work suggests that large, crater-free bands bordering the moon’s equator are wetlands fed by subsurface springs, where any incoming meteors would have made more of a splash than a bang. Those same springs may be the source of Titan’s polar lakes, feeding the world’s unusual liquid cycle.

“The complete lack of craters near the poles… People have noticed this for a while, but nobody’s had any good explanations,” says Catherine Neish of the Florida Institute of Technology in Melbourne. She wondered if craters there are simply melting away because the meteorites are landing in vast hydrocarbon swamps.

If Titan’s craters are being swallowed by soggy ground, then the ones we do see should appear more often at higher elevations, where the ground would be drier. To test this idea, Neish and her colleague Ralph Lorenz at the Johns Hopkins University Applied Physics Lab in Laurel, Maryland, examined a new map of Titan made from radar readings by NASA’s Cassini orbiter, published earlier this year. “It’s the first global topographic map of Titan that’s ever been made,” says Neish. “This is the first chance to really explore this issue quantitatively, instead of just qualitatively.” The team found that, statistically, more craters do exist at higher elevations all across the globe, while low zones have far fewer.>>

More at: https://www.newscientist.com/article/dn ... -on-titan/

[Tekija]

I am wondering how much is Camera Related....2007 is very clear, the others not so...with maybe static...then in 2015 is clear again. It also, appears to be "lower", then "more full"... but is "full" in 2007.

I would like to see the "full size" lake images of the times mentioned...to see any other changes around the lake.

:---[===] *

The shore on the opposite side of the peninsula also has changed quit a bit:

http://photojournal.jpl.nasa.gov/jpeg/PIA18430.jpg

[McMud]

.. so this is wherrre the oulde Nessy's gona ..

[Possesomuwi-awtossis]

Maybe it’s a drop in the level of Ligeia Mare. Some of the black inlets in the featured peninsula get smaller as the mysterious object comes into view, and larger again when it disappears. Would that be possible?

[neufer]

Maybe it’s a drop in the level of Ligeia Mare. Some of the black inlets in the featured peninsula get smaller as the mysterious object comes into view, and larger again when it disappears. Would that be possible?

They are "Radar images" so they would know exactly if the water level were changing.

[Ron Parker]

This is my first time on deck. I would like to ask a question: Are the fluid levels on Titan lake subject to rise and fall due to tidal forces? I was curious if it was possible that the mystery object (APOD March 7 2016) has not disappeared so much as become submerged. My observation is based on apparent solid surface material gaining and then lessening. -Ron Parker

[neufer]

This is my first time on deck. I would like to ask a question: Are the fluid levels on Titan lake subject to rise and fall due to tidal forces? I was curious if it was possible that the mystery object (APOD March 7 2016) has not disappeared so much as become submerged. My observation is based on apparent solid surface material gaining and then lessening.

Titan is tidally locked to Saturn so the "tides" do not change.

[Chris Peterson]

This is my first time on deck. I would like to ask a question: Are the fluid levels on Titan lake subject to rise and fall due to tidal forces? I was curious if it was possible that the mystery object (APOD March 7 2016) has not disappeared so much as become submerged. My observation is based on apparent solid surface material gaining and then lessening.

Titan is tidally locked to Saturn so the "tides" do not change.

The tidal force on Titan from Saturn is several hundred times greater than that of the Moon on the Earth. While Titan's orbital eccentricity is quite small, it is nevertheless large enough to allow for a fair degree of tidal flexing. I doubt that tides are significantly changing the height of surface liquids, but most certainly there are changing tides on Titan.