* Astronomy

Blobrana · L

RE: Titan

Blobrana · L

Title: Titan's transport-driven methane cycle
Authors: Jonathan L. Mitchell

The strength of Titan's methane cycle, as measured by precipitation and evaporation, is key to interpreting fluvial erosion and other indicators of the surface-atmosphere exchange of liquids. But the mechanisms behind the occurrence of large cloud outbursts and precipitation on Titan have been disputed. A gobal- and annual-mean estimate of surface fluxes indicated only 1% of the insolation, or ~0.04 W/m², is exchanged as sensible and/or latent fluxes. Since these fluxes are responsible for driving atmospheric convection, it has been argued that moist convection should be quite rare and precipitation even rarer, even if evaporation globally dominates the surface-atmosphere energy exchange. In contrast, climate simulations that allow atmospheric motion indicate a robust methane cycle with substantial cloud formation and/or precipitation. We argue the top-of-atmosphere radiative imbalance -- a readily observable quantity -- is diagnostic of horizontal heat transport by Titan's atmosphere, and thus constrains the strength of the methane cycle. Simple calculations show the top-of-atmosphere radiative imbalance is ~0.5-1 W/m² in Titan's equatorial region, which implies 2-3 MW of latitudinal heat transport by the atmosphere. Our simulation of Titan's climate suggests this transport may occur primarily as latent heat, with net evaporation at the equator and net accumulation at higher latitudes. Thus the methane cycle could be 10-20 times previous estimates. Opposing seasonal transport at solstices, compensation by sensible heat transport, and focusing of precipitation by large-scale dynamics could further enhance the local, instantaneous strength of Titan's methane cycle by a factor of several.

Read more (381kb, PDF)

Blobrana · L

Cassini Sees Tropical Lakes on Saturn Moon

Saturn's rings lie in the distance as the Cassini spacecraft looks toward Titan and its dark region called Shangri-La, east of the landing site of the Huygens Probe. Image Credit: NASA/JPL-Caltech/Space Science Institute

NASA's Cassini spacecraft has spied long-standing methane lakes, or puddles, in the "tropics" of Saturn's moon Titan. One of the tropical lakes appears to be about half the size of Utah's Great Salt Lake, with a depth of at least 1 metre.
The result, which is a new analysis of Cassini data, is unexpected because models had assumed the long-standing bodies of liquid would only exist at the poles. The findings appear in this week's issue of the journal Nature.
The latest results come from Cassini's visual and infrared mapping spectrometer, which detected the dark areas in the tropical region known as Shangri-La, near the spot where the European Space Agency's Huygens probe landed in 2005. When Huygens landed, the heat of the probe's lamp vaporized some methane from the ground, indicating it had landed in a damp area.
Read more

Blobrana · L

Expand (102kb, 1024 x 768)
Credit: NASA/JPL/Space Science Institute

This image of Titan was taken by the Cassini spaceprobe on the 6th May, 2012, when it was approximately 764,268 kilometres away.
The image was taken using the CL1 and CL2 filters.

Expand (87kb, 1024 x 768)
Credit: NASA/JPL/Space Science Institute

This image of Titan was taken by the Cassini spaceprobe on the 6th May, 2012, when it was approximately 770,352 kilometres away.
The image was taken using the CL1 and CB3 filters.

Blobrana · L

NASA Research Estimates How Long Titan's Chemical Factory Has Been in Business

Saturn's giant moon Titan hides within a thick, smoggy atmosphere that's well-known to scientists as one of the most complex chemical environments in the solar system. It's a productive "factory" cranking out hydrocarbons that rain down on Titan's icy surface, cloaking it in soot and, with a brutally cold surface temperature of around minus 270 degrees Fahrenheit, forming lakes of liquid methane and ethane.
However the most important raw ingredient in this chemical factory - methane gas, a molecule made up of one carbon atom joined to four hydrogen atoms - should not last for long because it's being continuously destroyed by sunlight and converted to more complex molecules and particles. New research from NASA-funded scientists attempts to estimate how long this factory has been operating. The results are presented as two papers appearing in the April 20 issue of the Astrophysical Journal.
Read more

Blobrana · L

Ontario Lacus

Blobrana · L

RE: Titan

Blobrana · L

Happy Birthday Titan!

On March 25, 1655, Dutch astronomer Christiaan Huygens, using a telescope he built himself, observed a small bright dot suspiciously close to the planet Saturn. Huygens correctly surmised that it might be a moon of that planet, and confirmed as much by following it in its orbit over the next few days.
We now know this distant moon, Titan, to be strangely one of the most Earthlike and most interesting worlds in the solar system.
Read more

Blobrana · L

Thousand-year wait for Titan's methane rain

Places on Saturn's moon Titan see rainfall about once every 1,000 years on average, a new analysis concludes.
Earth and Titan are the only worlds in the Solar System where liquid rains on a solid surface - though on Titan, the rain is methane rather than water.
The calculation is based on findings from the Cassini probe of rainstorms that occurred in 2004 and 2010.
Read more

Blobrana · L

Saturn and Titan

Saturn and Titan, side by side

Titan, Saturn's largest moon at 5150 km across, looks small here, pictured to the right of the gas giant in this infrared image taken by the Cassini spacecraft.
Saturn's rings appear across the top of the image, casting shadows onto the planet across the middle of the image.