Bright spots in a large lake on Titan suggest that Saturn's largest moon supports processes similar to Earth's water cycle, says Howard Zebker.
At first glance, Titan has little in common with Earth. The largest moon of Saturn, temperatures on Titan's surface dip nearly 300 F below zero, its seas slosh with liquid methane, and its sky is a murky shade of creamsicle.
Using data collected by Cassini's radar instruments, scientists have observed changes in Titan's liquid methane lakes and seas that indicate the moon experiences seasonal changes. (Image: NASA/JPL-Caltech)
And yet, fresh analysis of mysterious features spotted on the moon indicates that it experiences one of the same global processes that is important here on Earth.
In a study published in the latest issue of Nature Geoscience, scientists operating the Cassini satellite, including Stanford's Howard Zebker, present evidence that Titan has seasonal cycles analogous to Earth's, and that the moon's surface conditions change as the Titan year unfolds.
The Cassini satellite has been orbiting Saturn and its moons since 2004. Zebker, a professor of electrical engineering and of geophysics, is one of the lead scientists operating the spacecraft's radar instruments. Radar is critical for studying Titan in particular because the moon's atmosphere is typically too cloudy and thick for optical instruments to see through easily.
During five fly-bys of Titan's Ligeia Mare – a liquid methane sea larger than Lake Superior – the scientists noticed bright features that appeared and changed shape on the sea's surface. After ruling out a technical glitch or an exotic artifact of radar scattering, the group focused on three causes most likely for the phenomena.
"We are driven to use our imaginations and picture what could be happening on the sea to produce a transient feature," Zebker said.
One such explanation could involve low-density solids that usually sink below the surface – much like silt in a river delta – but then rise and clump together. Unlike ice on Earth, frozen methane is denser than its liquid phase, so it sinks instead of floats. "On Earth, ice floats and we get icebergs," Zebker said. "On Titan, icebergs would sink."
Seasonal temperature changes could account for the appearance and disappearance of these solids, as they might be released from the bottom and rise to the surface in warmer temperatures.
A second explanation involves bubbles. As summer temperatures warm the sea, bubbles trapped by the sunken frozen material could be released and float to the surface.
Finally, the bright features could be cresting waves, whipped up by summer winds.
"Waves are usually not visible on Titan, but in this case the onset of the summer season may create a more turbulent atmosphere," Zebker said. "On Earth we see this effect as the ocean warms and we start a new hurricane season."
All together, the observation and the possible explanations suggest that Titan's surface changes seasonally. They also support the idea that liquid methane might flow and evaporate in response to changing exposure to sunlight, in much the same way that water cycles through various systems on Earth.
Liquid methane lakes and seas have been observed on Titan's surface, and the atmosphere appears to carry methane and ethane similar to the way that Earth's atmosphere transports water vapor, Zebker said, and so scientists can expect Titan to have variations in liquid methane, ethane and other hydrocarbons driven by changes in temperature and sunlight.
As with any discovery that compares an alien world to Earth, the question of "Can it support life?" must be addressed. Although a dynamic process like the methane cycle and seasons go hand-in-hand with life on Earth, Zebker said that this discovery didn't significantly increase the chances that this moon of Saturn might support life.
"If there is sufficient energy pumped into Titan's atmosphere and surface from the sun, then it is possible that this would spawn evolution of life forms that take advantage of the energy source," Zebker said. "It would be very different life than on Earth, as it is minus 292 degrees Fahrenheit most of the time. Still, Titan remains one of the best places for life to evolve in the solar system."
Howard Zebker, Electrical Engineering and Geophysics: firstname.lastname@example.org
Bjorn Carey, Stanford News Service: (650) 725-1944, email@example.com
Howard Zebker | Eurek Alert!
Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter
17.08.2017 | Swansea University
Climate change: In their old age, trees still accumulate large quantities of carbon
17.08.2017 | Universität Hamburg
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
17.08.2017 | Physics and Astronomy
17.08.2017 | Earth Sciences
17.08.2017 | Physics and Astronomy