NASA’s epic Cassini shipment at Saturn still generates valuable scientific data more than three years after its death.
Data from one of the spacecraft’s last aircraft of Titan, a large moon with the forerunners of the chemistry of life, reveals that a large lake on the surface called Kraken Mare is more than 300 meters deep – it is approximately equal to the height of the Chrysler building in New York. In fact, the lake is so deep that Cassini’s radar could not investigate to the bottom.
Back in 2014, preliminary data from this flyby suggested that Kraken Mare was at least 35 meters deep, but extends further; the newly released results show that the lake is almost ten times deeper than the early estimate.
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Understanding the depth and composition of Kraken Mare will gradually reveal more about Titan’s mysterious chemistry, which is dominated by ethane and methane that accumulate in the pools, lakes and rivers on the surface, researchers said. The importance of the lake stems from the enormous size of Kraken Mare; if placed on earth, it would cover all five Great Lakes of North America.
“Kraken Mare … not only has a wonderful name, but also contains about 80% of the moon’s surface fluids,” said lead author Valerio Poggiali, a research fellow at the Cornell University Center for Astrophysics and Planetary Science, in a statement from the university said.
While the chemistry of Titan is strange compared to Earth, the geography of the moon is reminiscent of swampy or richer regions of our planet. Titan is also the only known moon in our solar system that boasts a thick atmosphere – a gaseous nitrogen shell, compared to the Earth’s mostly nitrogen-oxygen atmosphere.
This distinguishes Titan from the many moons in our solar system with little outer spheres or no atmosphere (like the earth’s moon) and from the potentially life-friendly “icy moons” where water ice covers an inland sea – such as on Jupiter’s Europe or Saturn’s Enceladus, which both inject water through the ice into space.
Data on Kraken Mare was collected during Cassini’s 104th flight from Titan on August 21, 2014, about three years before engineers deliberately threw the obsolete spacecraft into Saturn to avoid the small chance of accidentally contaminating the moon’s surface.
Kraken Mare was just one of the lakes on the mission’s list for those pilots. Researchers also wanted to look at Ligeia Mare – the site of a mysterious ‘magical island’ that regularly appears and disappears – and a smaller estuary called Moray Sinus, which researchers estimate is 85 meters deep, about the equivalent of the Statue of Liberty height. Cassini examined the lunar surface with its radar altimeter, about 965 kilometers away.
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Scientists calculated the sea depth by determining how long it took the radar signal to bounce back from the liquid surface and from the seabed, and comparing the difference between the depths and taking into account the composition of the liquid from the lakes, which is the energy of the radar signal.
The composition of Kraken Mare surprised scientists, along with its depth. It contains a mixture of methane and ethane, which differed from previous models suggesting that ethane would prevail due to the lake and geographical location of the lake’s poles. According to the researchers, the unexpected chemistry in the lake may help to better understand the precipitation cycle on Titan.
Scientists are also hoping to find out where the liquid methane on Titan comes from. Titan receives about 100 times less energy from the sun than the earth, as it is about 10 times farther away.
With the dim sunlight available, Titan converts methane into its atmosphere into ethane, but current models suggest that the moon must cycle through all the methane in just 10 million years, a small fraction of the lifespan of 4.5 billion year our solar system.
Engineers are working on a submarine concept that, if funded and approved by NASA, could launch in the 2030s to make Titan’s lakes shoot. Poggiali said the newly analyzed data from Cassini engineers could help better calibrate the sonar on board the vessel and understand the directional flow of the sea.
A study based on the research was published in December, in the Journal of Geophysical Research: Planets.
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