Scientists see storm brewing over Titan’s tropical desert

Washington, August 13 (ANI): A new research has discovered significant cloud formation within the tropical zone near the equator of Saturn’s largest moon, Titan, which is evidence that the parched, dry desert of the natural satellite can support large-scale storms.

The evidence comes from a team of US astronomers using the Gemini North telescope and NASA’s Infrared Telescope Facility (IRTF) both on Hawaii’s Mauna Kea.

Titan, the solar system’s second largest moon, has received considerable attention by scientists since NASA’s Cassini mission deployed the Huygens probe that descended through the moon’s atmosphere in January 2005.

During its descent, the probe’s cameras revealed small-scale channels and what appear to be stream beds in the equatorial regions that seemed to contradict atmospheric models predicting extremely dry desert-like conditions near the equator.

Until now, these erosional (fluvial) features have been explained by the possibility of liquid methane seeping out of the ground.

“In April 2008, we observed what was a global event that shows how storm activity in one region can trigger clouds, and probably rainfall, over arid regions, such as the tropics where Huygens landed,” said team member Henry Roe from Lowell Observatory.

Prior to this event (in April 2008), it was not known whether significant cloud formation was possible in Titan’s tropical regions.

This activity in Titan’s tropics and mid-latitudes also seems to have triggered subsequent cloud development at the moon’s south pole where it was considered improbable due to the Sun’s seasonal angle relative to Titan.

“Of course these rain showers are not liquid water like here on Earth, but are instead made of liquid methane. Just like the streambeds and channels that are carved by liquid water on Earth, we see features on Titan that have been created by flowing liquid methane,” Roe added.

The team monitored Titan on 138 nights over 2.2 years and during that time cloud cover was well under one percent.

Then, mid-April of 2008, just after team member Emily Schaller had handed in her doctoral dissertation focusing on Titan’s minimal cloud cover she noticed the dramatic increase in cloud cover.

During this three-week episode, clouds forming at about 30 degrees south latitude were observed, followed several days later by clouds closer to the equator and at the moon’s south pole.

The apparent connection between the cloud formations leads to the possibility that cloud formation in one area of the moon can instigate clouds in other areas by a process known as atmospheric teleconnections. (ANI)

Sulfate particles enhance climate warming properties of atmospheric soot

Washington, June 30 (ANI): A new study has found that particles of sulfate, thought to be holding climate change in check by reflecting sunlight, instead enhances warming when combined with airborne soot.

Recent atmospheric models have ranked soot, also called black carbon, second only to carbon dioxide in potential for atmospheric warming.

But particles, or aerosols, such as soot mix with other chemicals in the atmosphere, complicating estimates of their role in changing climate.

“Until now, scientists have had to assume how soot is mixed with other chemical species in individual particles and estimate how that ultimately impacts their warming potential,” said Kimberly Prather, professor in the Department of Chemistry and Biochemistry and the Scripps Institution of Oceanography at the University of California, San Diego.

“Our measurements show that soot is most commonly mixed with other chemicals such as sulfate and this mixing happens very quickly in the atmosphere. These are the first direct measurements of the optical properties of atmospheric soot and allow us to better understand the role of soot in climate change,” she added.

For the study, Prather and Ryan Moffet, a former graduate student at UC San Diego who is now at the Lawrence Berkeley National Laboratory, measured atmospheric aerosols over Riverside, California and Mexico City.

Using an instrument that measures the size, chemical composition and optical properties of aerosols in real time, they showed that jagged bits of fresh soot quickly become coated with a spherical shell of other chemicals, particularly sulfate, nitrate, and organic carbon, through light-driven chemical reactions.

Within several hours of sunrise, most of the atmospheric carbon they measured had been altered in this way.

Particles of sulfate or nitrate alone reflect light, and some have proposed pumping sulfate aerosols into the atmosphere to slow climate change.

But, these chemicals play a different role when they mix with soot.

“The coating acts like a lens and focuses the light into the center of the particle, enhancing warming,” Prather said.

“Many people think sulfate aerosols are a good thing because they are highly reflective and cool our planet,” he said.

“However, we are seeing that sulfate is commonly mixed with soot in the same particles, which means in some regions sulfate could lead to more warming as opposed to more cooling as one would expect for a pure sulfate aerosol,” he added.

Their measurements showed that in the atmosphere the lens-like shell of sulfate and nitrate enhances absorption of light by coated soot particles 1.6 times over pure soot particles. (ANI)