Methane concentrations revealing a plume in Mars' northern
hemisphere during its summer season. Credit: NASAMethane on Mars? Really? What does that mean?

We've known about the existence of methane gas on Mars for several years now, from independent observations.  Further observations have led to the detection of "plumes" or clouds of methane gas apparently emanating from specific locations on Mars.  One plume is estimated to contain 19,000 metric tons of the stuff.

Why is this exciting news? If you know anything about the source of most of Earth's atmospheric methane gas, you already know the answer:  possible life.  Not, I should say, necessarily life on Mars, but maybe a strong piece of evidence in that direction.

On Earth, methane (CH₄) is produced by living organisms—mostly by the activity of microbes, but some by the digestive processes in larger organisms (yes, like humans, and cows).  Methane is the major constituent of natural gas, which fuels gas powered ovens and heaters in homes, as well as natural gas power plants.  Methane is also produced by decaying organic matter—that's where "swamp gas" comes from.

On Mars, methane gas cannot exist for long in the atmosphere; it is relatively quickly broken down by solar radiation.  So, the methane detected in Mars' atmosphere must be replenished by something, continually.

So the big question right now is, where is the methane coming from? Under the surface of Mars, almost certainly.  By biological processes—life—underground? Could be.  By non-biological means? Could be, too; methane can be produced through inorganic chemical processes.  We don't know yet.  The next step in finding out more will be the Mars Science Laboratory, a large rover scheduled to be launched to Mars sometime in the near future.

In one form or another, humans have been trying to see, or find, life on Mars for a long time.  Percival Lowell squinted at Mars' small, blurry disk through his 24-inch telescope in Flagstaff, and perceived markings he saw to be vast canal complexes, ostensibly built by a desert Martian civilization thirsty for water harvested from their planet's polar ice caps. This led to much of the science fiction relating to life on Mars in the 20^th Century.

Earth-bound telescopes noted seasonal changes in Mars' color and brightness, and some attributed this to possible seasonal growth of Martian vegetation—though it was later found that these variations were the effects of seasonal planet-wide dust storms.

The Viking landers' primary mission in the 1970's was to search for life.  They didn't find any by scratching around Mars' surface and testing the soils there.

The 1990's saw the controversy over microscopic structures in meteorites found on Earth but determined to have originated on Mars.  Some argued that these structures were fossils of Martian microbes that lived on Mars long ago.  Whether these findings were in fact fossils and not just geologic structures was never conclusive.

The determination that liquid water once flowed on the surface of Mars, and still exists under its surface at least as ice, is pretty much scientific fact today.  Evidence of past liquid flows have been imaged and mapped from space, and the Phoenix lander found water ice in the north polar regions last year.  And there's the rover Opportunity that has confirmed gray hematite, a mineral that forms in the presence of water.

It's almost certain that there are no Martian cows grazing the rusty desert plains out there.  But there seems to be a lot of evidence for the possibility that something is going on below Mars' surface—perhaps the presence of liquid water, perhaps the presence of some form of life.  We don't know yet, but it sure feels like we're onto something here….

Unless our sewage happens to end up in the Bay and in the headlines, most of us probably never give a second thought to where our wastewater is headed each time we run the tap or flush the toilet.

To learn more about the travels of sewage, I took a tour of the Las Gallinas Valley Sanitary District treatment plant led by Plant Manager Matt Pierce. The plant has been in operation for about 50 years and serves over 30,000 residents in north San Rafael.

After leaving sinks and showers throughout the District, wastewater travels through a network of pipes and pump stations. Once the sewage arrives at Las Gallinas, it passes through an inlet screen and a grit chamber, which together remove much of the dense, inorganic material-"like diamond rings," Matt jokes.

A lot of what happens at the plant is not that different from what happens in your compost pile: "It's basically bacteria at work," Matt points out. (The much bigger challenge for sanitation districts these days are all the unnatural things we're putting down the drain: household chemicals, personal care products, pharmaceuticals.)

From the grit chamber the sewage heads into a series of clarifiers, where gravity causes the organic solids to settle out. The biosolids pass through a thickener and then an anaerobic digester-the most, ahem, aromatic stop on our tour. After further thickening in storage ponds, the sludge is injected into a disposal field.

Meanwhile, the liquid from the clarifiers travels through two biofilters, where rotating arms spray the water over rock beds. The organic matter in the wastewater is a feast for microbial slime living on the rocks. In the nitrification tower, more microorganisms break down the ammonia in the water. In the final stages of treatment, the wastewater is chlorinated to kill any remaining bacteria, then dechlorinated since the chlorine is toxic to many aquatic species. Finally, the treated water is sprayed onto District fields or discharged into Miller Creek where it flows to San Pablo Bay.

The District has done a lot to minimize the environmental impacts of its operations. The plant is powered by a field of solar panels. The methane released in the sludge treatment process is captured and used to generate power and heat the digester. Some of the treated wastewater supports acres of fresh and saltwater wetlands-in fact the District's land is a favorite local gem for walkers and birders. And in a partnership with the Marin Municipal Water District, more than a million gallons of treated wastewater are recycled daily for landscape irrigation and other projects.

There are plans to make even fuller use of the reclaimed water. The Bay Institute-in partnership with the Sonoma County Water Agency, Las Gallinas, and three other North Bay sanitation agencies-has developed a plan to use recycled water for wetland and creek restoration and for agricultural irrigation. Legislation sponsored by Congressman Mike Thompson to establish the program passed the House late last year; Senator Dianne Feinstein has introduced similar legislation that we are hopeful will pass this year.

With California's growing demands for water, such creative means to conserve and recycle are critical to helping prevent this precious resource from just going "down the drain."


Ann Dickinson is Communications Manager for The Bay Institute (www.bay.org), a nonprofit research, education, and advocacy organization dedicated to protecting and restoring San Francisco Bay and its watershed, "from the Sierra to the sea."

When football fans tune in on Super Bowl Sunday next weekend, they'll be watching a greener Super Bowl, according to the NFL. Demand for carbon credits is booming, with companies from Dell Computer to Enterprise Rent-a-Car offering their customers offsets with their purchases. But critics are concerned that consumers don't know what they're buying – or might not be getting what they're promised.

The 2006 Word of the Year was "carbon netural" in the The New Oxford English Dictionary. But there's still a lot of debate about what it means. Many people compare the U.S. carbon offset market to the Wild West. Since there is no regulation, how do you know what you're buying?

There are several guides to carbon offsets that have been created by non-profit organizations, designed to help the average consumer (see related resources). But part of the problem is that many people are still debating what a carbon offset should be. And that's a debate that can be found in the blogosphere.

One place you can find it is on the Grist.org blog which has many bloggers writing about green issues. Forestry offset projects, which sell credits based on the fact that trees sequester– or hold carbon dioxide, have come under fire. You can read about a few of the critiques here, here and here.

Another blog, Treehugger.com, has followed the issue as well. They posted this comparison of offset providers to help their readers do their homework and this more in depth guide on the issues buyers should be aware of.

Of course, one of the earliest debates over offsets was whether offsets would act as "indulgences", distracting consumers from making concrete changes in their lifestyles to reduce their carbon footprint. Terrapass, one offset retailer, has tried to investigate this by surveying their customers. They found that the majority of them had already had green habits. Still, the virtues of offsets are a matter of personal opinion.

You may listen to the "Cashing in on Carbon" radio report online, as well as find additional links and resources.

Lauren Sommer is an Associate Media Producer for QUEST.

latitude: 37.325510, longitude: -120.640341