IceCube neutrino detector is running hot

Now that we know how to find high energy neutrinos, we're seeing lots.

by Chris Lee - Jan 23 2014, 7:00am EST  

The building that houses the IceCube servers.

USAP.gov

With the IceCube detector now in operation at the South Pole, the first results are starting to come in, and boy are they interesting. IceCube monitors a volume of one cubic kilometer of ice for muons, the byproduct of neutrinos colliding with the ice. What makes IceCube different is that it is looking especially for very high energy neutrinos. In the lower energy range, neutrinos are products of things generated very locally (in astronomical terms). Although these events are interesting, they swamp those that are produced at great distances, making it difficult to use neutrinos as a window into the Universe.

However, very distant and highly energetic events should produce neutrinos with a correspondingly high energy. If we can detect them, maybe they can tell us about those high-energy events. This idea is more than 30 years old—until now, the technology has simply not been up to the task.
IceCube consists of some 8000 photomultiplier tubes (light detectors), strung out on strings, buried under the ice of the Antarctic. Each photomultiplier tube contains its own data processing computer that provides some preliminary filtering and enables event signals to be synchronized to within 2ns.
These signals are then sent to a local computing center that sits at the center of the array (yes, in Antarctica), which does more processing before sending it out to the world.

Further Reading

Coolest jobs in tech (literally): running a South Pole data center

You know it's cold when you have to heat the air used to cool your data center.

Both the instrument and neutrino physics are exquisitely well understood, so the scientists working with the detector have just a single percent uncertainty in their models and another ten percent uncertainty in the instrumentation. Considering everything, that is a fine piece of hardware. However, even buried deeply in the ice, IceCube has a devil of a time finding the neutrinos it is looking for. The instrument records 2700 cosmic rays per second, and a locally produced neutrino turns up every six minutes. The cosmic signal, in contrast is ten neutrinos... per year.
After a fairly long run and a particular type of analysis, the collaboration running IceCube was rather confused; they hadn't found any neutrinos of interest yet. So they took a look inside their processing and found a particular type of event that was being incorrectly filtered out. The problem was an assumption about the energy range they were after.
At high energies (but not too high), a neutrino will tend to collide with an atom outside the volume occupied by the detectors. The resulting high energy muon streaks off like a meteor through the ice, losing energy through radiation, production of electrons and positrons, and other things. IceCube looks for these tracks and figures out where the neutrino came from. (It should be noted that some of these neutrinos have traveled through the entire Earth before being detected.)
Once you go to even higher energies, however, neutrinos that are detected are a result of collisions from within the detector. Again the muon motors off, causing havoc, but the event track began from within the detector volume—a pattern that the researchers initially excluded. They are now actually spotting neutrinos in the 1000TeV range (The LHC operates around 14TeV).
At these energies, the particles have quite a high probability of interacting with atoms, so they don't make it through the Earth; instead, they're detected quite close to the surface of the ice. Even better, because the tracks begin within the detector volume, the energy of the neutrinos can be calculated with high accuracy
After recognizing the problem, a reanalysis produced around 30 neutrinos, and many more are expected to be reported in May. The big question is whether these neutrinos are evenly distributed across the sky (as low energy neutrinos are), or if they have specific sources. At present, there is not enough data to say. As with any small data set, it has a few blobs that look like they may be specific sources, but we should expect those to disappear as more neutrinos are detected.

Pope Francis explains why the Internet is a 'gift from God'

Keith Wagstaff NBC News    

21 hours ago

Twitter

 

Not as many followers as Justin Bieber, but not bad.

This pope has wasted no time in embracing the Internet.
A week after Jorge Mario Bergoglio was declared pope in a puff of white smoke in March, he sent out his first tweet as Pope Francis, which was retweeted 36,457 times. His account, @Pontifex, now has more than 3.5 million followers.

His predecessor, Pope Benedict XVI , also embraced social media, calling it "a great opportunity" for users to establish a "Christian-style presence" online. He started the papal Twitter account, launched a Vatican YouTube channel and even released a Facebook application called Pope2You.
Francis, despite not having a Twitter account as a cardinal, has praised the Internet as well, calling it a "gift from God" in a statement on Thursday. Still, the pope, like most people, has some reservations about our new digital age.

• This pretty much sums up Twitter: "The speed with which information is communicated exceeds our capacity for reflection and judgement, and this does not make for more balanced and proper forms of self-expression." 
• On the Internet "filter bubble": "The variety of opinions being aired can be seen as helpful, but it also enables people to barricade themselves behind sources of information which only confirm their own wishes and ideas, or political and economic interests."  
• Beware, World of Warcraft players: "The desire for digital connectivity can have the effect of isolating us from our neighbours, from those closest to us."  

Overall, however, the pope seemed bullish on the Internet. He certainly hasn't been shy in utilizing it, occasionally angering both conservatives and liberals with his 140-character messages. He angered the free-market crowd with tweets like this.

 

Some liberals, on the other hand, took offense on Wednesday when he tweeted this in support of an anti-abortion rally.

Despite the Internet's flaws, His Holiness isn't likely to cancel the Vatican's broadband plan anytime soon. The pontiff's advice: The Internet is cool, as long as it leads to good deeds IRL.

"While these drawbacks are real, they do not justify rejecting social media; rather, they remind us that communication is ultimately a human rather than technological achievement," he wrote. "It is not enough to be passersby on the digital highways, simply 'connected'; connections need to grow into true encounters."

Keith Wagstaff writes about technology for NBC News. He previously covered the tech beat for TIME's Techland and wrote about politics as a staff writer at TheWeek.com. You can follow him on Twitter at @kwagstaff and reach him by email at: Keith.Wagstaff@nbcuni.com

La. Teacher Tells Buddhist Student He's 'Stupid' And Bible is '100 Percent True'

 

By Allison Geller, Thu, January 23, 2014

 

The American Civil Liberties Union of Louisiana is suing the Sabine Parish School Board on behalf of a family who alleges that their son, a Buddhist, suffered from racial discrimination at his school. His teacher told students that Buddhists were “stupid” and led the class to laugh at him. The school regularly proselytized the Christian faith.

According to the ACLU complaint filed in the U.S. District Court in Louisiana, the main offender, science teacher Rita Roark at Negreet High School, teaches students that evolution is “impossible” while the Bible is “100 percent true.”

Roark’s science tests include questions like “"ISN'T IT AMAZING WHAT THE _____________ HAS MADE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!" According to Scott Lane, the stepfather of “C.C.,” Roark marked his test wrong when he wrote “Lord Buddha” and “belittled him in front of the entire class” when he wrote nothing.

A student stated in class that "people are stupid if they think God is not real." Roark responded, "Yes! That is right! I had a student miss that on his test," to which the whole class laughed.

C.C, who is of Thai descent, has been a Buddhist his whole life. Yet he was subject to regular Christian prayer in class, religious iconography, Bible versus scrolling on the electronic marquee in front of the building, and a large picture of Jesus over the school’s main doors.

C.C.’s parents tried to bring up their complaints with school board superintendent Sarah Ebarb. Ebarb responded, “this is the Bible belt,” and advised C.C. to “change” his religion. She also suggested that the Lanes transfer C.C. to a school where “there are more Asians.” They did, in fact, transfer him—C.C. was having such bad anxiety at that it made him physically ill—but they encountered discrimination there, too.

"The treatment this child and his family have endured is not only disgraceful, it's unconstitutional," said Heather L. Weaver, senior staff attorney for the ACLU Program on Freedom of Religion and Belief. 

The U.S. Department of Education and U.S. Department of Justice will also investigate the school board at the ACLU’s request.

Sources: ACLU (2)

A new wrinkle in the control of waves: Flexible materials could provide new ways to control sound and light

by David Chandler

Flexible, layered materials textured with nanoscale wrinkles could provide a new way of controlling the wavelengths and distribution of waves, whether of sound or light. The new method, developed by researchers at MIT, could eventually find applications from nondestructive testing of materials to sound suppression, and could also provide new insights into soft biological systems and possibly lead to new diagnostic tools.

The findings are described in a paper published this week in the journal Physical Review Letters, written by MIT postdoc Stephan Rudykh and Mary Boyce, a former professor of mechanical engineering at MIT who is now dean of the Fu Foundation School of Engineering and Applied Science at Columbia University.

While materials' properties are known to affect the propagation of light and sound, in most cases these properties are fixed when the material is made or grown, and are difficult to alter later. But in these layered materials, changing the properties—for example, to "tune" a material to filter out specific colors of light—can be as simple as stretching the flexible material.

"These effects are highly tunable, reversible, and controllable," Rudykh says. "For example, we could change the color of the material, or potentially make it optically or acoustically invisible."

The materials can be made through a layer-by-layer deposition process, refined by researchers at MIT and elsewhere, that can be controlled with high precision. The process allows the thickness of each layer to be determined to within a fraction of a wavelength of light. The material is then compressed, creating within it a series of precise wrinkles whose spacing can cause scattering of selected frequencies of waves (of either sound or light).

Surprisingly, Rudykh says, these effects work even in materials where the alternating layers have almost identical densities. "We can use polymers with very similar densities and still get the effect," he says. "How waves propagate through a material, or not, depends on the microstructure, and we can control it," he says.

By designing that microstructure to produce a desired set of effects, then altering those properties by deforming the material, "we can actually control these effects through external stimuli," Rudykh says.
"You can design a material that will wrinkle to a different wavelength and amplitude. If you know you want to control a particular range of frequencies, you can design it that way."

The research, which is based on computer modeling, could also provide insights into the properties of natural biological materials, Rudykh says. "Understanding how the waves propagate through biological tissues could be useful for diagnostic techniques," he says.

For example, current diagnostic techniques for certain cancers involve painful and invasive procedures. In principle, ultrasound could provide the same information noninvasively, but today's ultrasound systems lack sufficient resolution. The new work with wrinkled materials could lead to more precise control of these ultrasound waves, and thus to systems with better resolution, Rudykh says.

The system could also be used for sound cloaking—an advanced form of noise cancellation in which outside sounds could be completely blocked from a certain volume of space rather than just a single spot, as in current noise-canceling headphones.

"The microstructure we start with is very simple," Rudykh says, and is based on well-established, layer-by-layer manufacturing. "From this layered material, we can extend to more complicated microstructures, and get effects you could never get" from conventional materials. Ultimately, such systems could be used to control a variety of effects in the propagation of light, sound, and even heat.

The technology is being patented, and the researchers are already in discussions with companies about possible commercialization, Rudykh says.

Explore further: Light and sound fire scientists' imaginations: Researchers lead review of photonic, phononic metamaterials

   

How Grazing Cows Can Save the Planet, and Other Surprising Ways of Healing the Earth

January 12, 2014

By Dr. Mercola

Judith Schwartz is a freelance writer and author of the book Cows Save the Planet: And Other Improbable Ways of Restoring Soil to Heal the Earth. I recently met Judy at a conference held by Allan Savory of the Savory Institute in Boulder, Colorado.
The Savory Institute helps farmers to holistically manage their livestock in order to improve soil quality and heal the environment. In fact, according to Savory, an African ecologist, dramatically increasing the number of grazing livestock is the only thing that can reverse desertification (when land turns to desert).
This was Savory's first conference, and turned out to be quite a memorable event. Judy has summarized a big portion of what was presented in that conference in her book. But what made her hone in on the issue of soil health to begin with?
Surprisingly, it all began with an investigation into the economy. Around 2008, just before the economic downturn, she'd started writing about the transition movement:

"One of the things that transition initiatives were dealing with was local currencies," she says. "Looking into local currencies kind of helped me understand how local economies work and primed me to ask questions when the economic downturn hit, like 'What is money? What is wealth?'

I was on that trajectory, writing about environmental economics and new economics... Basically, it's the notion that our economy can and should serve the people the planet as opposed to the other way around.

This I fear is the scenario that we've kind of gotten stuck in – that people and the planet, meaning all of our natural systems, exist to serve the economy.

From that framework, I started looking at ecology and observed the disconnect between our financial system and the natural world, which just cannot be separate. That disconnect doesn't work."

The Environmental Impact of Conventional Farming

This led her to learn more about soil health, economical land use, and how modern agricultural practices affect our environment.
 

For example, did you know that our modern agricultural system is responsible for putting more carbon dioxide into the atmosphere than the actual burning of fossil fuels? Understanding this reveals an obvious answer to pressing global problems.

There are only three places for carbon to go: land, air and water. Our agricultural practices have removed massive amounts of valuable carbon from land, transferring it into air and water. By paying greater attention to carbon management, we have the opportunity to make a dramatic difference in this area, which is having major negative consequences to our agriculture, and the pollution of our water and air.
As explained by Judy, early this past summer, concentrations of atmospheric CO2 crossed the 400 parts per million-threshold—the highest it's been in thousands of years. According to an organization called 350.org, scientists believe our CO2 levels need to be around 350 parts per million in order to maintain favorable living conditions on earth.

Carbon management is a critical aspect of environmental health and the growing of food.
That said, CO2 levels are not constantly or continuously rising in a straight line. The level rises and falls, and this is a clue to what's going on.

"Depending on the season, depending on how much photosynthesis is happening, it dips down, and then goes up again," Judy explains. "When we've got a lot of plants, as we get towards the warmer part of the year, more photosynthesis is happening, and the CO2 levels drop slightly.

That's so important to know, because photosynthesis is key to what we're talking about.

When I talk about bringing carbon back into the soil, I'm talking about supporting and stimulating the process of photosynthesis – in other words, growing more plants. Those plants then take in the CO2. They make carbon compounds. Those carbon compounds are drawn down, and they go into the soil."

Sequestering carbon in the Earth's soils is a good thing. There's actually more carbon in our world soils than in all plants, including trees, and the atmosphere together. However, due to modern agricultural methods, we've lost between 50 and 80 percent of the carbon that used to be in the soil... This means there's plenty of "room" to put it back in.

"It's useful to understand that the notion of bringing carbon back into the soil, one thing that it does is withdraw carbon down from the atmosphere. That's hugely important," Judy says.

"Carbon is the main component of soil organic matter. That's the good stuff that you want in soil anyway for fertility. It also absorbs water. When you have carbon-rich soil, you also have soil that is resilient to floods and drought. When you start looking at soil carbon, the news keeps getting better and better."

The Importance of Holistic Herd Management

Another major factor that needs to be considered is the management of livestock. Herds raised according to modern, conventional practices contribute to desertification—turning land into desert—which, of course, doesn't support plant life and photosynthesis, thereby shifting the equation in the wrong direction. When land turns to desert, it no longer holds water, and it loses the ability to sustain microbial life and nourish plant growth...
One of the reasons Allan Savory has become so popular is his promotion of holistic herd management, which causes desert areas to convert back to grasslands that support plant life. As explained by Judy:

"It occurred to him that the land needed the animals in the same way that the animals needed the land. He began to really observe how animals functioned on land, and came to understand the really intricate dynamics, the system, that had been naturally in operation.

Basically, when grazing animals graze, they're nibbling on the grasses in a way that exposes their growth points to sunlight and stimulates growth... Their trampling [of the land also] did several things: it breaks any capped earth so that the soil is aerated. It presses in seeds [giving them] a chance to germinate, so you have a greater diversity of plants. [Grazing herds] also press down dying and decaying grasses, so that they can be better acted upon by microorganisms in the soil. It keeps the decaying process going. Their waste also fertilizes the soil."

This natural symbiotic relationship between animals, soils and plants—where each benefits the other mutually—is a powerful insight. And it's one that can be replicated with great benefit. Besides the environmental benefits, grass-fed, pastured livestock is also an excellent source of high quality meat. In fact, it's the only type of meat I recommend eating, as raising cattle in confined animal feeding operations (CAFOs) alters the nutritional composition of the meat—not to mention such animals are fed antibiotics, growth promoters and other veterinary drugs.

You Can Make a Difference in More Ways Than One  

As for recommendations for what we can do to get us going in the right direction with regards to improving not only animal and human health but the health of the planet, Judy says:

"Most recommendations are very simple. The simplest thing is to avoid having bare soil. Because when you have bare uncovered soil, the land degradation process begins. When you have bare soil, that means that the carbon is binding with oxygen and becoming carbon dioxide."

We also need to shift our focus to emphasize the biological system as a whole. Soil is not a static "thing." It's a living symbiotic system, and soil microorganisms also play a very important role in this system. When I visited Elaine Ingham at the Rodale Institute, I learned the value of compost tea for promoting beneficial soil microbes, and I now use a vortex compost tea brewing system to revitalize my own garden. Interestingly, the better you farm or garden, the less land you need. According to Judy, a biological farmer using appropriate methods can grow on 1,000 acres the same amount of food another farmer might need 5,000 acres to produce...
 

Another factor is the importance of integrating animals on the land. Most biological farmers understand this, and will tell you that in order for soil to get to its highest potential of productivity and health, there needs to be animals on the land. (According to Savory, grazing large herds of livestock on half of the world's barren or semi-barren grasslands could also take enough carbon from the atmosphere to bring us back to preindustrial levels!) But what if you're not a gardener yet, or a farmer? How can you help achieve this much needed shift?

"I think people can make a difference in all sorts of ways that people make decisions every day, such as asking yourself how the food you're buying was grown," Judy says. "Because once you start asking where the food comes from, even posing that question, will lead you to make different choices.

Apart from food, what decisions are being made in your community about the use of land? Can your community save money by working with soil rather than, say, putting in an expensive waste or water treatment plant? That's another thing, getting involved on a local level. There are all kinds of organizations that are working on different environmental and different food aspects locally and nationally, etc."

Biological Farming Solves Many Pressing Problems

My first passion and career was being a physician, then an Internet educator, and now I'm moving into high-performance biological agriculture because I really believe it's the next step in our evolution. We must shift the way we produce food because the current system is unsustainable. And while this information really is ancient, it's not widely discussed. There's only a small segment of the population that even understands this natural system, and the potential it has for radically transforming the way we feed the masses AND protect the environment at the same time.
 

I thoroughly agree with the recommendation to get involved personally, because it's so exciting. For me, it's become a rather addictive hobby. Once you integrate biological farming principles, you can get plant performances that are 200-400 percent greater than what you would typically get from a plant! What's more, not only does it improve the quantity, it also improves the quality of the food you're growing. These facts should really be at the forefront of everybody's mind when they think about farming, as it's the solution to so many pressing problems. Judy agrees, noting:

"The challenge is that we've been led to believe that our agricultural model, which is an extractive model, is the way it needs to be. But we can shift to a regenerative model. That's where we need to go."

Final Thoughts

As Judy says, there's a lot to be optimistic about, because whether we're talking about the degradation of the environment or our food supply, there are answers!

"Many people just sort of give up and say, 'I can't do anything about this.' I was speaking to someone the other day who said that her son, who just finished college, said, 'You know, it's over. We're doomed.' To me, that is just so sad. How can we let the next generation feel that way? I think that betrays a huge lack of imagination. Because when we talk about our environmental challenges, one thing we don't talk about is nature's desire to heal itself. Once we ally with that natural process, it's amazing what we can do."

Ending the burning of fossil fuels is not the one and only way for us to turn the tide on rising carbon dioxide levels. Granted, solar energy and wind power would certainly be preferable to burning fossil fuels. But even if we didn't stop burning fossil fuels, we can still reverse rising CO2 levels by addressing the way we farm, using sound, time-honored agricultural principles.

And—something else to consider—even if we completely stop burning fossil fuels but do not change agriculture, we'll still be left with problems like lands turning to desert, flooding, and drought for example. In short, we really must address how we manage our lands and soils... You can learn more about biological farming by reviewing the related articles listed in the right-hand side bar on this page. I also highly recommend Judy's book, Cows Save the Planet: And Other Improbable Ways of Restoring Soil to Heal the Earth. It's a great read for anyone wanting to learn more about this topic.

Habitability, Taphonomy, and the Search for Organic Carbon on Mars

John P. Grotzinger

Science 24 January 2014:
Vol. 343 no. 6169 pp. 386-387
DOI: 10.1126/science.1249944                        

+ Author Affiliations

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.

1. E-mail: grotz@gps.caltech.edu

 

The quest for extraterrestrial life is an old and inevitable ambition of modern science. In its practical implementation, the core challenge is to reduce this grand vision into bite-sized pieces of research. In the search for organic remnants of past life, it is enormously helpful to have a paradigm to guide exploration. This begins with assessing habitability: Was the former environment supportive of life? If so, was it also conducive to preservation of organism remains, specifically large organic molecules?

 

The 2004 arrival of the Mars Exploration Rovers (MERs) Spirit and Opportunity provided a chance to investigate ancient aqueous environments in situ and deduce their likelihood of supporting life. Initial results confirmed what data from orbiters had long suggested—that diverse aqueous environments existed on the surface of Mars billions of years ago. The success of the MERs led to the development of the Mars Science Laboratory (MSL) mission. The Curiosity rover landed at Gale crater in 2012 and was designed to specifically test whether ancient aqueous environments had also been habitable. In addition to water, did these ancient environments also record evidence for the chemical building blocks of life (C, H, N, O, P, S), as well as chemical and/or mineralogic evidence for redox gradients that would have enabled microbial metabolism, such as chemoautotrophy?

Curiosity also has the capability to detect organic carbon, but it is not equipped for life detection.

Image taken by the Mars Hand Lens Imager of the John Klein drill hole (1.6 cm in diameter) at Yellowknife Bay reveals gray cuttings of mudstone (ancient lake sediments), rock powder, and interior wall.                                                

An array of eight ChemCam laser shot points can be seen. The gray color suggests that reduced, rather than oxidized, chemical compounds and minerals dominated the pore fluid chemistry of the ancient sediment. A cross-cutting network of sulfate-filled fractures indicates later flow of groundwater through fractures after the sediment was lithified.

CREDIT: NASA/JPL-CALTECH/MALIN SPACE SCIENCE SYSTEMS

Five articles presented in full in the online edition of Science (www.sciencemag.org/extra/curiosity), with abstracts in print, describe the detection at Gale crater of a system of ancient environments (including streams, lakes, and groundwater networks) that would have been habitable by chemoautotrophic microorganisms. The Hesperian age (<∼3.7 billion years) rocks mentioned in these articles are at the young end of the spectrum of ancient martian aqueous environments. Yet, a sixth article details a more ancient and also potentially habitable environment detected in Noachian age (>∼3.7 billion years) rocks at Meridiani Planum. A seventh article describes the present radiation environment on the surface of Mars at Gale crater and its influence on the preservation of organic compounds in rocks.

 

Opportunity landed at Meridiani Planum on 25 January 2004. Coincident with the 10th anniversary of this landing, Arvidson et al. report the detection of an ancient clay-forming, subsurface aqueous environment at Endeavour crater, Meridiani Planum. Though Opportunity does not have the ability to directly detect C or N, it has been able to establish that several of the other key factors that allow for the identification of a formerly habitable environment were in place. This potentially habitable environment stratigraphically underlies and is considerably older than the rocks detected earlier in the mission that represent acidic, hypersaline environments that would have challenged even the hardiest extremophiles. The presence of both Fe⁺³- and Al-rich smectite clay minerals in rocks on the rim of the Noachian age Endeavour impact crater were inferred from the joint use of hyperspectral observations by the Mars Reconnaissance Orbiter and extensive surface observations by the Opportunity rover. The rover was guided tactically by orbiter-based mapping. Extensive leaching and formation of Al-rich smectites occurred in subsurface groundwater fracture systems.

Grotzinger et al. show that an ancient habitable environment existed at Yellowknife Bay, Gale crater, where stream waters flowed from the crater rim and pooled in a curvilinear depression at the base of Gale's central mountain to form a lake-streamgroundwater system that might have existed for millions of years. Vaniman et al. provide evidence for moderate to neutral pH, as shown by the presence of smectite clay minerals and the absence of acid-environment sulfate minerals, and show that the environment had variable redox states due to the presence of mixed-valence Fe (magnetite) and S (sulfide, sulfate) minerals formed within the sediment and cementing rock. McLennan et al. show that lake salinities were low because of the very low concentration of salt in the lake deposits.

Elemental data indicate that clays were formed in the lake environment and that minimal weathering of the crater rim occurred, suggesting that a colder and/or drier climate was prevalent.

Ming et al. show that the thermal decomposition of rock powder yielded NO and CO₂, indicating the presence of nitrogen- and carbon-bearing materials. CO₂ may have been generated by either carbonate or organic materials. Concurrent evolution of O₂ and chlorinated hydrocarbons indicates the presence of oxychlorine species. Higher abundances of chlorinated hydrocarbons in the lake mudstones, as compared with modern windblown materials, suggest that indigenous martian or meteoritic organic C sources are preserved in the mudstone. However, the possibility of terrestrial background sources brought by the rover itself cannot be excluded.

 

These results demonstrate that early Mars was habitable, but this does not mean that Mars was inhabited. Even for Earth, it was a formidable challenge to prove that microbial life existed billions of years ago—a discovery that occurred almost 100 years after Darwin predicted it, through the recognition of microfossils preserved in silica (1). The trick was finding a material that could preserve cellular structures. A future mission could do the same for Mars if life had existed there.
Curiosity can help now by aiding our understanding of how organic compounds are preserved in rocks, which, in turn, could provide guidance to narrow down where and how to find materials that could preserve fossils as well. However, it is not obvious that much organic matter, of either abiologic or biologic origin, might survive degradational rock-forming and environmental processes. Our expectations are conditioned by our understanding of Earth's earliest record of life, which is very sparse.

 

Paleontology embraces this challenge of record failure with the subdiscipline of taphonomy, through which we seek to understand the preservation process of materials of potential biologic interest. On Mars, a first step would involve detection of complex organic molecules of either abiotic or biotic origin; the point is that organic molecules are reduced and the planet is generally regarded as oxidizing, and so their preservation requires special conditions. For success, several processes must be optimized. Primary enrichment of organics must first occur, and their destruction should be minimized during the conversion of sediment to rock and by limiting exposure of sampled rocks to ionizing radiation. Of these conditions, the third is the least Earth-like (Earth's thick atmosphere and magnetic field greatly reduce incoming radiation). Curiosity can directly measure both the modern dose of ionizing cosmic radiation and the accumulated dose for the interval of time that ancient rocks have been exposed at the surface of Mars.

 

Hassler et al. quantify the present-day radiation environment on Mars that affects how any organic molecules that might be present in ancient rocks may degrade in the shallow surface (that is, the top few meters). This shallow zone is penetrated by radiation, creating a cascade of atomic and subatomic particles that ionize molecules and atoms in their path. Their measurements over the first year of Curiosity's operations provide an instantaneous sample of radiation dose rates affecting rocks, as well as future astronauts. Extrapolating these rates over geologically important periods of time and merging with modeled radiolysis data yields a predicted 1000-fold decrease in 100–atomic mass unit organic molecules in ∼650 million years.

 

Sediments that were buried and lithified beneath the radiation penetration depth, possibly with organic molecules, would eventually be exhumed by erosion and exposed at the surface. During exhumation, organics would become subject to radiation damage as they entered the upper few meters below the rock-atmosphere interface. The time scale of erosion and exhumation, and thus the duration that any parcel of rock is subjected to ionizing radiation, can be determined by measuring cosmogenically produced noble gas isotopes that accumulate in the rock. ³⁶Ar is produced by the capture of cosmogenic neutrons by Cl, whereas ³He and ²¹Ne are produced by spallation reactions on the major rock-forming elements. Farley et al. show that the sampled rocks were exposed on the order of ∼80 million years ago, suggesting that preservation of any organics that accumulated in the primary environment was possible, although the signal might have been substantially reduced.

 

Wind-induced saltation abrasion of the rocks in Yellowknife Bay appears to have been the mechanism responsible for erosion and exhumation of the ancient lake bed sampled by Curiosity. The geomorphic expression of this process is a series of rocky scarps that retreated in the downwind direction. Understanding this process leads to the prediction that rocks closest to the scarps were most recently exhumed and are thus most likely to preserve organics, all other factors being equal. In this manner, the MSL mission has evolved from initially seeking to understand the habitability of ancient Mars to developing predictive models for the taphonomy of martian organic matter. This parallels the previous decade, in which the MER mission turned the corner from a mission dedicated to detecting ancient aqueous environments to one devoted to understanding how to search for that subset of aqueous environments that may also have been habitable.

References

1. ↵
   1. S. A. Tyler,
   2. E. S. Barghoorn

   , Occurrence of structurally preserved plants in Pre-Cambrian rocks of the Canadian Shield. Science 119, 606–608 (1954).

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Why do biofuels help prevent global warming?

Engines running on biofuels emit carbon dioxide (CO2), the primary source of greenhouse gas emissions, just like those running on gasoline. However, because plants and trees are the raw material for biofuels, and, because they need carbon dioxide to grow, the use of biofuels does not add CO2 to the atmosphere, it just recycles what was already there. The use of fossil fuels, on the other hand, releases carbon that has been stored underground for millions of years, and those emissions represent a net addition of CO2 to the atmosphere. Because it takes fossil fuels – such as natural gas and coal – to make biofuels, they are not quite “carbon neutral.”

Argonne National Laboratory has carried out detailed analyses of the “well-to-wheels” greenhouse gas emissions of many different engine and fuel combinations. The chart at right shows a few selected examples. Argonne’s latest analysis shows reductions in global warming emissions of 20% from corn ethanol and 85% from cellulosic ethanol. Thus,

 

 greenhouse gas emissions in an E85 blend using corn ethanol would be 17% lower than gasoline, and using cellulosic ethanol would be 64% lower. A separate analysis found that biodiesel reduces greenhouse gas emissions by 41%; thus, a B20 blend would achieve a reduction of about 8%.

Cellulosic ethanol achieves such high reductions for several reasons:
1. Virtually no fossil fuel is used in the conversion process, because waste biomass material, in the form of lignin, makes an excellent boiler fuel and can be substituted for coal or natural gas to provide the heat needed for the ethanol process.

2. Farming of cellulosic biomass is much less chemical- and energy-intensive than farming of corn.

3. Perennial crops store carbon in the soil through their roots, acting as a carbon “sink” and replenishing carbon in the soil. Switchgrass, for example, has a huge root system that penetrates over 10 feet into the soil and weighs as much as one year’s growth aboveground (6-8 tons per acre).                                    

“Cellulosic ethanol is at least as likely as hydrogen to be an energy carrier of choice for a sustainable transportation sector.” – Natural Resources Defense Council, Union of Concerned Scientists

Compared to conventional diesel fuel, the use of biodiesel results in an overall reduction of smog-forming emissions from particulate matter, unburned hydrocarbons, and carbon monoxide, as shown at right. Biodiesel slightly increases nitrogen oxide emissions, by about 2% in a B20 blend. Sulfur oxides and sulfates, which are major components of acid rain, are not present in biodiesel.

As for ethanol, the oxygen atom in the ethanol molecule leads to more complete fuel combustion and generally fewer emissions. E10 blends have been credited with reducing emissions of carbon monoxide by as much as 30% and particulates by 50%. However, mixing low levels of ethanol (2% to 10%) with gasoline increases the blend’s tendency to evaporate and contribute to low-level ozone unless the gasoline itself is adjusted. This problem diminishes with higher levels of ethanol. At blends between 25% and 45%, the fuel is equivalent to gasoline, and at higher blends it is less evaporative. E85 has about half the volatility (tendency to evaporate) of gasoline.

The effect of E85 on air quality is almost uniformly positive, with the exception of increased emissions of aldehydes, such as acetaldehyde. Conventional catalytic converters control these emissions in ethanol blends of up to 23%, and it is expected that they could be readily adapted to E85 blends. A test of advanced emission control systems in three conventional gasoline vehicles found that advanced systems reduced formaldehyde emissions by an average of 85% and acetaldehyde by an average of 58%.

Even without advanced controls, the benefits of reducing other toxic emissions outweigh the effects of aldehydes. The National Renewable Energy Laboratory tested a 1998 Ford Taurus FFV running on E85 and reported: “Emissions of total potency weighted toxics (including benzene, 1,3-butadiene, formaldehyde, and acetaldehyde) for the FFV Taurus tested on E85 were 55% lower than that of the FFV tested on gasoline.”

Emissions characteristics of E85* Actual emissions will vary with engine design; these numbers reflect the potential reductions offered by ethanol (E85), relative to conventional gasoline. • Fewer total toxics are produced. • Reductions in ozone-forming volatile organic compounds of 15%. • Reductions in carbon monoxide of 40%. • Reductions in particulate emissions of 20%. • Reductions in nitrogen oxide emissions of 10%. • Reductions in sulfate emissions of 80%. • Lower reactivity of hydrocarbon emissions. • Higher ethanol and acetaldehyde emissions. * Estimates based on ethanol’s inherently “cleaner” chemical properties with an engine that takes full advantage of these fuel properties. – U.S. Environmental Protection Agency

The principal contributor to toxic air pollution from gasoline is a class of chemical compounds called aromatics, which make up an average of 26% of every gallon of gasoline. Blended with gasoline to increase octane, aromatics have the potential to cause cancer, and they also result in emissions of fine particulates and smog-forming gases that harm lung function and worsen asthma.

 

The EPA was required by the Clean Air Act Amendments of 1990 to seek “the greatest degree of emission reduction achievable” of air toxics in automobiles. In response to recent litigation, the EPA issued a rule to reduce one of these hazardous air pollutants, benzene, but the agency did not address the two other aromatic compounds, toluene and xylene, which form benzene during combustion. Using biofuels instead of aromatics to improve octane would result in public health benefits worth tens of billions of dollars from the reduction in emissions of small particles alone.                                      
Native perennial grasses such as switchgrass had to be tough to survive on the prairie. They are deep-rooted and drought-resistant and require less water than food crops. They also need less fertilizer, herbicide, insecticide, and fungicide per ton of biomass than conventional crops.

Switchgrass is an approved cover crop under the Conservation Reserve Program because it prevents soil erosion and filters runoff from fields planted with traditional row crops. Buffer strips of switchgrass, planted along stream banks and around wetlands, can remove soil particles, pesticides, and fertilizer residues from surface water before they reach ground water or streams.

There are enough varieties of prairie grass and other sources of cellulosic biomass that farmers need not all rely on a single energy crop – so-called monocultures. Indeed, recent research suggests that mixed prairie grasses may be more productive than monocultures. One study found that a diverse mixture of grasses grown on degraded land would yield 51% more energy per acre than ethanol from corn grown on fertile land.

In general, perennial energy crops create more diverse habitats than annual row crops, attracting more species and supporting larger populations. Switchgrass fields are popular with hunters, as they provide habitat for many species of wildlife, including cover for deer and rabbits and a nesting place for wild turkey and quail – and pheasants, as shown at right. As long as farmers avoid work that would disturb the birds during nesting or breeding seasons, their fields will remain popular with wildlife.