Snowing with Microbes on Enceladus?

Aside from ancient Mars, the moons of Saturn might be one of the best places to look for life outside this planet. The methane lakes of Titan are promising places, but so are the spewing plumes of ice on Enceladus — and the latter would be an easy one to check, as it turns out. The Cassini orbiter just flew through them, and Cassini scientists want to go back and take a longer look.

Cassini has been examining Enceladus‘ ghostly, icy plumes for several years now, tasting the water, ice and organic material flying out of them. (Organic meaning carbon-based compounds, not necessarily living material.) The plumes are also piping hot, at least in distant solar system terms — about -120 degrees F, which equates to lots of thermal energy. And perhaps the most tantalizing part? The icy particles are salty, possessing the same salinity as Earth’s oceans.

Enceladus might have a vast interior sea, and it also has an energy source in the form of massive tidal forces courtesy of its planet. Saturn’s wrenching gravitational pull flexes Enceladus’ interior, generating heat. Heat and salty water sounds a lot like environments on Earth — like subterranean microbe communities in places like Yellowstone, or perhaps the thriving ecosystems that exist in hydrothermal vents in the absence of sunlight. Could Enceladus host any such life forms?

Enceladus Jets Dramatic plumes spray water ice from many locations near the south pole of Saturn's moon Enceladus. More than 30 individual jets of different sizes can be seen in this image captured during a flyby from NASA's Cassini spacecraft on Nov. 21, 2009. NASA/Cassini Imaging Science Team

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It would be fairly simple to find out, according to Carolyn Porco, a renowned Cassini scientist and leader of the spacecraft’s imaging science team. All you’d need to do is fly by and take a whiff.

“It sounds crazy, but it could be snowing microbes on the surface of this little world,” she says in an interview with NASA’s science news portal. “It’s the most promising place I know of for an astrobiology search. We don't even need to go scratching around on the surface. We can fly through the plume and sample it. Or we can land on the surface, look up and stick our tongues out.  And voilà…we have what we came for.”

Simply flying through the plume would be easier than designing an interplanetary boat, at least.

 Enceladus: Cassini flew just 46 miles above Enceladus' south pole on March 27, 2012, cruising right through the spewing plumes seen here. This image is from 2009.  NASA/Cassini Imaging Science Team

 Environment Clean Generations

A Portion of Mars could be Friendly to Life

Sunrise at Gale Crater Gale Crater, future home of the Mars Science Laboratory, looms in the distance, distinguished from adjacent craters by its central mountain. Gale Crater straddles the dichotomy boundary of Mars, which separates the broad, flat, and young northern plains from the much older and rougher southern highlands. Water may have flowed across this topographic boundary, from highland to lowland. Last week, the Opportunity rover team found slam-dunk evidence of liquid water on the surface of Mars, an intriguing find for astrobiology. NASA/JPL-Caltech

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Now that we have slam-dunk evidence that Mars was once a wet and likely temperate place, astrobiologists are pondering the implications for ancient Martian life. One new study says the Red Planet has even more habitable space than Earth — albeit underground.

Led by Charley Lineweaver at the Australian National University, researchers compared models of temperature and pressure conditions on Earth with those on Mars, extrapolating how much of Mars might be amenable to hosting Earth-like organisms. Life occupies just one percent of Earth, if you consider the entire planet’s volume from the core to the stratosphere. But apparently three percent of Mars could be habitable, Lineweaver said. Most of this comfortable space is underground, where there would be sufficient pressure and warmth to hold liquid water and perhaps some toasty microbes.



Although the Phoenix lander found ice at the north pole, modern Mars’ surface is too low-pressure to hold on to liquid water, and it’s too cold (average about -81 °F) for water or life as we know it. But nestled underneath the planet’s crust, the habitat could be much more friendly, Lineweaver told AFP.
Lineweaver said his study uses decades of data from a host of Mars missions and compiles information about several sites, rather than just one or two areas. “There are large regions of Mars that are compatible with terrestrial life,” he said.

The Mars Science Laboratory, en route to the planet for an August arrival, is designed to help answer some of these questions. It has several instruments for examining the chemical composition of rocks inside Gale Crater, a region believed to once host flowing water. The Curiosity rover also has some instruments designed to look for the chemical ingredients of life.

The Australian study was published in the journal Astrobiology.

How Low Can Life Go?

• The byproducts of rock-eating microbes have been found pouring out of a hole in the sea floor


• The unidentified microbe that live in the rocks could be widespread in the oceans.


• How much these subterranean, submarine microbes contribute to the global carbon budget is still unknown. 

There is a thriving realm of mysterious microbes of potential importance to the global carbon budget hidden beneath the sea floor near where the Earth's crust is being pulled apart, according to new evidence from deep-sea explorers.

In the frigid depths of the Juan de Fuca tectonic plate off the coast of the Pacific Northwest, warm water moving through the sea floor near the plate edges has been found loaded with dissolved organic matter with a telltale carbon signature that could have only come from microbes in the rocks.

The warm waters were captured as they poured from an old bore-hole and into the freezing waters, and were double-checked for contamination by comparing them to waters obtained from sterile, specially made samplers that were driven into the sea floor.

"It looks like a massive fire hose," said Matthew McCarthy of the University of California at Santa Cruz, referring to the pressurized, 80-degree Fahrenheit groundwater spewing from the old hole in the sea bottom. McCarthy is one of the authors of a paper about the secrets of that groundwater, being published in the January issue of the journal Nature Geoscience.

The goal of the work, McCarthy explained, was to irrefutably show that the waters from the hole were representative of what lies much deeper, rather than just contaminated by the human activities that drilled the hole.

"If there was ever any contamination, it was long gone," McCarthy said of he and his colleagues conclusions.

Indeed, now the researchers have evidence of what is probably a vast volume of lava rocks going down to unknown depths which are loaded with microbes. Those microbes make their living by using reactions on the surface of basalt rocks that have been erupted over the millennia on the seafloor.

The microbes belong to a group called called chemo-litho-autotrophs that live without any connection to the more common Earth ecosystems which are dependent on sunlight.

Such microbial ecosystems could be widespread in the oceans. If they are, they could play an important and unknown role in the cycling of carbon in the deep seas, said McCarthy.

"If these kinds of reactions are happening at Juan de Fuca, chances they are happening at other places are very high," agreed researcher Katrina Edwards of the University of Southern California. "The potential is pretty widespread."

So far the actual identities of the microbes is unknown, said McCarthy. "Our data don't tell you about the microbes that made it," he said.

Although some microbes have been found, it's not clear they are the source of the dissolved organic carbon in the water.

As for how it fits into the Earth's carbon budget, that's still unknown, says Edwards. She likes to visualize the carbon budget as being made of many carbon cycles that are like gears of different sizes and turning at different speeds.

 

"This one is moving slowly and we don't know how big it is," she said of the deep sea, chemo-litho-autotroph carbon cycle.

One thing that will help to begin defining its size will be more work on other seafloor spreading centers. Edwards and her team are planning just that, with a new observatory slated to be installed on the Mid-Atlantic Ridge in late 2011.

by "environment clean generations"