“We call it fishing for electrons.” That’s environmental engineer Craig Criddle describing a new way that he and his colleagues have discovered for generating electricity from sewage.

Wait. What?

Brilliant, right? The Stanford team hopes this breakthrough technology will be used to harvest energy in places such as sewage treatment plants, or to break down organic pollutants in the “dead zones” of lakes and coastal waters where fertilizer runoff and other organic waste can deplete oxygen levels and suffocate marine life.

And this new power all starts with wired microbes. The mini power plants produce electricity as they digest plant and animal waste from wastewater. Right now, still in the laboratory phase, their prototype is about the size of a D-cell battery and looks like a chemistry experiment, with two electrodes, one positive, the other negative, plunged into a bottle of wastewater.

Inside that murky vial, attached to the negative electrode like barnacles to a ship’s hull, an unusual type of bacteria feast on particles of organic waste and produce electricity, which is captured by the battery’s positive electrode.

Scientists have long known of the existence of what they call exoelectrogenic microbes—organisms that evolved in airless environments and developed the ability to react with oxide minerals rather than breathe oxygen as we do, to convert organic nutrients into biological fuel.

Over the past dozen years or so, several research groups have tried various ways to use these microbes as bio-generators, but tapping this energy efficiently has proven challenging. Part of that challenge for the Stanford team is the cost of the oxide minerals necessary to make it happen. “We demonstrated the principle using silver oxide, but silver is too expensive for use at large scale,” says team member Yi Cui. “Though the search is underway for a more practical material, finding a substitute will take time.”

The Stanford engineers estimate that the microbial battery can extract about 30 percent of the potential energy locked up in wastewater. That is roughly the same efficiency at which the best commercially available solar cells convert sunlight into electricity.

Their study was published recently in the Proceedings of the National Academy of Sciences.

Image: Xing Xie, Stanford University

As the key to life on Earth, water has also become the key to looking for life on other worlds…

Water on Earth flows through a cycle that most children learn about in elementary school. Some scientists hope that if we notice a cycle on another planet then it could hint at the existence of liquid water: if we find a cycle, then we may find water, and we may find life. So the idea goes.

Observations of Saturn’s moon Enceladus reveal geyser jets on its south pole. The jets let out a plume of vapor whose magnitude varies according to predictable times. A paper on the plume cycle, published in the journal Nature, analyzes data from NASA’s Cassini spacecraft to study the patterns of ejection from under the ice-covered moon.

“The jets of Enceladus apparently work like adjustable garden hose nozzles,” said Matt Hedman, the paper’s lead author and a Cassini team scientist based at Cornell University. “The nozzles are almost closed when Enceladus is closer to Saturn and are most open when the moon is farthest away.”

The Cassini team observed the jets for the first time in 2005 soon after the spacecraft entered Saturn’s orbit. The team hypothesized that the intensity of the jets would vary over time, but they did not directly observe any variation until they examined over 200 photos taken from the mission.

The images show that the southern plume becomes about four times brighter while Enceladus lies far from Saturn, and dims while it is close. Why? It may have something to do with recent findings about Saturn’s gravitational influence on Enceladus…

The research team believes that Saturn’s gravity squeezes Enceladus and causes the changes in geyser strength. When Enceladus is closer to Saturn, the geyser openings tighten up, allowing less material to escape. When Enceladus relaxes at farther distances, the spray can escape in larger quantities.

“The way the jets react so responsively to changing stresses on Enceladus suggests they have their origins in a large body of liquid water,” said Christophe Sotin, a co-author and Cassini team member. “Liquid water was key to the development of life on Earth, so these discoveries whet the appetite to know whether life exists everywhere water is present.”

So if we follow the water, perhaps we will find life…?

By the way, you can visit Enceladus in Morrison Planetarium! From now through September 5th, check out Fragile Planet at the California Academy of Sciences.

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA/JPL-Caltech/University of Arizona/Cornell/SSI

Roughly 70% water, Earth’s surface is covered with rivers, lakes, oceans, mud, and rain clouds. Scientists searching for alien life are searching for planets similar to our own, because experience tells us that life needs water in order to survive.

NASA’s Cassini spacecraft began photographing Titan, one of Saturn’s moons, in 2004. The pictures beamed back to Earth depict strange lakes and rivers. The European Space Agency (ESA)’s Huygens probe splashed into Titan’s mud in 2005, further convincing researchers that Titan was indeed “wet.”

The scientific community agrees that Titan appears Earth-like, but at temperatures around –290°F (–180°C), any water would be in the form of ice. Instead, astronomers believe any wetness on the surface of Titan is a combination of liquid methane, ethane, and other hard-to-freeze elements.

Apparently this moon doesn’t resemble Earth at all. Alex Hayes, a planetary scientist at Cornell University who works on the Cassini radar team, noticed something eerie while observing Saturn’s moon. “Where are all the waves?”

Wind, raindrops, and tides move Earth’s water in every direction. But Cassini has detected no wave action on Titan. It’s pretty strange, especially because, “[w]e know there is wind on Titan, the moon’s magnificent sand dunes prove it,” says Hayes.

Taking into account Titan’s gravity (one seventh that of Earth’s), the nature of fluids on its surface, and its dense atmosphere, Hayes and his colleagues calculated and published the speed needed for waves to form: only two miles per hour!

A strange puzzle, with even stranger solutions. Maybe the lakes are covered with tar, damping wave motion. Or they might be frozen. Or perhaps the wind hasn’t reached two miles per hour… yet.

Most of the lakes are located on Titan’s northern hemisphere, where it has been winter for a few years. The air during winter is colder and thicker, and may be the secret behind the missing waves.

If current climate models are correct, Cassini should be able to detect waves as Titan nears its summer solstice in 2017. Measurements and calculations of waves formed during the summer could tell us the chemical composition of Titan’s lakes… And reveal more about this Earth-like world so unlike Earth.

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA/JPL-Caltech/USGS

A leggy neighbor

The leggiest animal on the planet lives just south of San Francisco, according to a new report in ZooKeys. Illacme plenipes comes the closest to the description of a millipede than any of its relatives—females have as many as 750 legs!

Even millipede researcher Paul Marek thinks Illacme plenipes is special. Its plentiful legs have claws and National Geographic News lists more of its cool features:

…massive antennae (relative to the scale of its body), which the millipede uses to feel its way through the dark; a jagged and translucent exoskeleton; and body hairs that produce a sort of silk that may help Illacme plenipes adhere to the undersides of boulders. And unlike in other millipedes, the mouth of this species is specifically structured for piercing and sucking plant tissues.

Wanna get to know your neighbor? Movies and images are available for download here.

Insect hearing aids

A recent publication in Science explores how certain rainforest katydids are able to listen like mammals do, but much more efficiently. Katydids’ hearing organs are near the insects’ knees, and much like human ears, gather sounds from the air and transmit them to the brain in fluids.

For humans and other mammals, sounds are collected by the eardrums in vibrations, which are transferred by three ear bones to the cochlea. Fluid in the cochlea translates these sounds and sends them to the brain.

In katydids, the ear bones are missing, simplifying the process. (An excellent comparison illustration is available at Scientific American.) This simplification could lead to better hearing aids for humans, according to the lead author of the study, Fernando Montealegre-Z. “These findings change our views on insect hearing and open the way for designing ultrasensitive bio-inspired sensors.”

Insect-inspired water bottles

Finally, recent news reports describe a new company creating water-collecting bottles for “the most arid regions of the world.” Their inspiration? The Namib Desert beetle. Wired UK describes the insects’ process of water collection:

The beetle survives by collecting condensation from the ocean breeze on the hardened shell of its wings… The beetle extends and aims the wings at incoming sea breezes to catch humid air; tiny droplets 15 to 20 microns in diameter eventually accumulate on its back and run straight down towards its mouth.

Want more exciting entomology?

How about disease-fighting ladybirds? Learn more at ScienceShot. Insect movie stars? Watch their cameos at the New York Times.

Katydid image: Fernando Montealegre-Z and Daniel Robert

Since the mid-1960s, the Palmer Drought Severity Index (PDSI) has been the standard of measuring drought, reviewing temperature and rainfall information over a period of time. But a recent study in Nature states that the measurement may be too simple.

The PDSI looks at potential moisture evaporation from the soil in terms of temperature and plant use. But researchers at Princeton University see other clues to evaporation—wind speed, humidity and solar radiation—that could contribute to the evaporation and drought estimation.

The Intergovernmental Panel on Climate Change (IPCC) uses the PDSI to assess drought. In their 2007 report, they noted that droughts have intensified since the 1970s. But the Princeton team finds that there has been little change in droughts over the past 60 years. According to Science Now,

… the new assessment technique found that between 1980 and 2008, the global area stricken by drought grew by approximately 0.08% per year—less than one-seventh the increase estimated by the temperature-only version of PDSI…

The results of the study have implications for how we interpret the role of global warming on changes to the weather and its extremes like drought. The authors stress that this finding does not rule out drought as a response to future climate change. It just gives scientists a better way to measure and predict drought.

Tomorrow: Sustainable groundwater

This week, we’ll look at recent research on water and climate. Today we’ll start in the past, to understand how climate and water affected human life hundreds of years ago.

The collapse of the Maya is one of the world’s most enduring mysteries. But a recent study in the journal Science, combining a precise climatic record of the Maya environment with a precise record of Maya political history, may provide a better understanding of the role weather had in the civilization’s rise and fall.

And it all has to do with water—plentiful rainfall, followed by drought. The researchers studied the isotopes in 2,000 year-old stalagmite samples from a cave in Belize. Nature News describes the process:

The team estimated historical rainfall in the Mayan lowlands by measuring oxygen isotopes incorporated into the stalagmite from rainwater that seeped into the cave from the ground above. The precipitation levels were tied to specific dates by measuring the ratio of radioactive isotopes in the stalagmite.

“Unusually high amounts of rainfall favored an increase in food production and an explosion in the population between AD 450 and 660,” says Douglas Kennett, lead author and professor of anthropology at Penn State. This high amount of rainfall, he says, was followed “by a series of major droughts that triggered a decline in agricultural productivity and contributed to societal fragmentation and political collapse. The most severe drought (AD 1020 and 1100) in the record occurs after the widespread collapse of Maya state centers and may be associated with widespread population decline in the region.”

Social unrest is often tied to drought and food availability. If drought should persist because of global warming in the future, perhaps we can learn from the Maya, says co-author Bruce Winterhalder, of UC Davis. “It’s a cautionary tale about how fragile our political structure might be. Are we in danger the same way the Classic Maya were in danger? I don’t know.”

Tomorrow: Are droughts overestimated?

Image: Douglas Kennett, Penn State

This is exciting as it gives us more evidence that the dry, red planet used to be wet with water. There is earlier evidence for the presence of water on Mars, but this evidence—images of rocks (like the one to the right) containing ancient streambed gravels—is the first of its kind. The sizes and shapes of stones in these images offer clues to the speed and distance of a long-ago stream’s flow.

“From the size of gravels it carried, we can interpret the water was moving about three feet per second, with a depth somewhere between ankle and hip deep,” says Curiosity science co-investigator William Dietrich of UC Berkeley. “Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we’re actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it.”

“The shapes tell you they were transported and the sizes tell you they couldn’t be transported by wind. They were transported by water flow,” concurs Curiosity science co-investigator Rebecca Williams of the Planetary Science Institute.

The science team may use Curiosity to learn the elemental composition of the material, revealing more characteristics of the wet environment that formed these deposits.

The slope of Mount Sharp in Gale Crater remains the rover’s main destination. Clay and sulfate minerals detected there from orbit can be good preservers of carbon-based organic chemicals that are potential ingredients for life.

“A long-flowing stream can be a habitable environment,” says Mars Science Laboratory project scientist John Grotzinger of Caltech. “It is not our top choice as an environment for preservation of organics, though. We’re still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment.”

Image: NASA/JPL-Caltech/MSSS

Groundwater

Groundwater was the subject of three studies and several articles in May. Two of the studies look at the effect of pumped groundwater on sea level rise, and both papers agree that groundwater has had a significant impact on global sea level rise. Nature News has details from both the Nature Geoscience study and the Geophysical Research Letters study. Science News does, too, and gives the details in context:

In recent years, sea level has been rising around 3.1 millimeters each year. Besides groundwater depletion, other major contributors include the melting of glaciers and polar ice fields, and the expansion of ocean water as it heats up.

Over at National Geographic Newswatch, Sandra Postel laments the out-of-sight, out-of-mind nature of groundwater. She gives her most endangered aquifer list and includes a video to raise awareness about groundwater depletion.

A study this week in the Proceedings of the National Academy of Sciences highlights the increase in groundwater use in California and Texas. The study’s authors used water level records from thousands of wells, data from NASA’s GRACE satellites, and computer models to study groundwater depletion in the two regions. GRACE satellites monitor changes in Earth’s gravity field that are controlled primarily by variations in water storage.

Irrigation for agriculture is the main cause of groundwater depletion, and the researchers urge more efficient and sustainable irrigation practices before it’s too late.

So little water…

Did you see this fabulous illustration (above, right) of all the world’s water? It was distributed by USGS in mid-May. Please read the fascinating description at their site.

Earlier this week, the Academy and its partners in the Worldviews Network released a short Google Earth based film on global water issues. Like the USGS illustration, it gives perspective of Earth’s available water. It also plunges users into water issues relevant at global and regional scales—especially relevant to the dry American Southwest. You can also play around with the liquid data on your own, using Google Earth.

Local drinking holes

UC Berkeley researchers have developed floating robots to work with smart phones and monitor water flow, especially in river systems like the all-important Sacramento-San Joaquin River Delta. Scientists hope that having a high volume of sensors moving through the water can shed light on processes influenced by water movement, such as the spread of pollutants, the migration of salmon, or the mixing of salt and fresh water in the Delta’s ecosystem. More information is available here.

Thirsty for more?

Scientific American has an in-depth report on the freshwater crisis—including an interesting infographic on water usage by country. Nature News describes a Canadian “laboratory” of lakes on the verge of closure. And an upcoming experiment in the Grand Canyon will see if more water will restore ecosystems for native fish, the New York Times reports.

Image: USGS

It is known that biologically diverse streams are better at cleaning up pollutants than less rich waterways, so Bradley Cardinale of the University of Michigan created 150 miniature model streams to find out why this is.

The model streams use recirculating water in flumes to mimic the variety of flow conditions found in natural streams. Cardinale grew between one and eight species of algae in each of the mini-streams, then measured each algae community’s ability to soak up nitrate, a nitrogen compound that is a nutrient pollutant of global concern. He found that nitrate uptake increased linearly with species richness. On average, the eight-species mix removed nitrate 4.5 times faster than a single species of algae grown alone.

The reason? Niche partitioning, Cardinale said.

In the stream experiments, each algae species was best adapted to a particular habitat in the stream and gravitated to that location—its unique ecological niche. As more algae species were added, more of the available habitats were used, and the stream became a bigger, more absorbent sponge for nitrate uptake and storage.

Sound familiar? Think Charles Darwin. “People as far back as Darwin have argued that species should have unique niches and, as a result, we should see a division of labor in the environment,” Cardinale said.

This is exciting news because nitrate is an ingredient in many fertilizers and is found in surface runoff from agricultural land that makes its way into streams, lakes and coastal zones. It is a leading cause of degraded water quality worldwide.

“The primary implication of this paper is that naturally diverse habitats are pretty good at cleaning up the pollutants we dump into the environment, and loss of biodiversity through species extinctions could be compromising the ability of the planet to clean up after us,” according to Cardinale.

Image credit: Danuta Bennett