Silicon-capped hydrocarbons: Mysterious molecules in space

This graph shows absorption wavelength as a function of the number of carbon atoms in the silicon-terminated carbon chains SiC_(2n+1)H, for the extremely strong pi-pi electronic transitions. 

When the chain contains 13 or more carbon atoms, not significantly longer than carbon chains already known to exist in space, these strong transitions overlap with the spectral region occupied by the elusive diffuse interstellar bands. 

Credit: D. Kokkin, ASU

Over the vast, empty reaches of interstellar space, countless small molecules tumble quietly though the cold vacuum.

Forged in the fusion furnaces of ancient stars and ejected into space when those stars exploded, these lonely molecules account for a significant amount of all the carbon, hydrogen, silicon and other atoms in the universe.

In fact, some 20 percent of all the carbon in the universe is thought to exist as some form of interstellar molecule.

Many astronomers hypothesize that these interstellar molecules are also responsible for an observed phenomenon on Earth known as the "diffuse interstellar bands," spectrographic proof that something out there in the universe is absorbing certain distinct colours of light from stars before it reaches the Earth.

But since we don't know the exact chemical composition and atomic arrangements of these mysterious molecules, it remains unproven whether they are, in fact, responsible for the diffuse interstellar bands.

Now in a paper appearing this week in The Journal of Chemical Physics, from AIP Publishing, a group of scientists led by researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. has offered a tantalising new possibility: these mysterious molecules may be silicon-capped hydrocarbons like SiC3H, SiC4H and SiC5H, and they present data and theoretical arguments to back that hypothesis.

At the same time, the group cautions that history has shown that while many possibilities have been proposed as the source of diffuse interstellar bands, none has been proven definitively.

"There have been a number of explanations over the years, and they cover the gamut," said Michael McCarthy a senior physicist at the Harvard-Smithsonian Center for Astrophysics (CfA) who led the study.

Molecules in Space and How We Know They're There
Astronomers have long known that interstellar molecules containing carbon atoms exist and that by their nature they will absorb light shining on them from stars and other luminous bodies.

Because of this, a number of scientists have previously proposed that some type of interstellar molecules are the source of diffuse interstellar bands, the hundreds of dark absorption lines seen in color spectrograms taken from Earth.

In showing nothing, these dark bands reveal everything. The missing colours correspond to photons of given wavelengths that were absorbed as they travelled through the vast reaches of space before reaching us.

More than that, if these photons were filtered by falling on space-based molecules, the wavelengths reveal the exact energies it took to excite the electronic structures of those absorbing molecules in a defined way.

Armed with that information, scientists here on Earth should be able to use spectroscopy to identify those interstellar molecules, by demonstrating which molecules in the laboratory have the same absorptive "fingerprints."

But despite decades of effort, the identity of the molecules that account for the diffuse interstellar bands remains a mystery.

Nobody has been able to reproduce the exact same absorption spectra in laboratories here on Earth.

"Not a single one has been definitively assigned to a specific molecule," said Neil Reilly, a former postdoctoral fellow at Harvard-Smithsonian Center for Astrophysics (CfA) and a co-author of the new paper.

Now Reilly, McCarthy and their colleagues are pointing to an unusual set of molecules, silicon-terminated carbon chain radicals, as a possible source of these mysterious bands.

As they report in their new paper, the team first created silicon-containing carbon chains SiC3H, SiC4H and SiC5H in the laboratory using a jet-cooled silane-acetylene discharge.

They then analysed their spectra and carried out theoretical calculations to predict that longer chains in this family might account for some portion of the diffuse interstellar bands.

However, McCarthy cautioned that the work has not yet revealed the smoking gun source of the diffuse interstellar bands.

To prove that these larger silicon capped hydrocarbon molecules are such a source, more work needs to be done in the laboratory to define the exact types of transitions these molecules undergo, and these would have to be directly related to astronomical observations.

But the study provides a tantalising possibility for finding the elusive source of some of the mystery absorption bands, and it reveals more of the rich molecular diversity of space.

"The interstellar medium is a fascinating environment," McCarthy said. "Many of the things that are quite abundant there are really unknown on Earth."

More information: The Journal of Chemical Physics, July 29, 2014. DOI: 10.1063/1.4883521

NASA JPL CARVE: Arctic Permafrost the "Sleeping Giant" of Climate Change

Flying low and slow above the pristine terrain of Alaska's North Slope research scientist Charles Miller of NASA's Jet Propulsion Laboratory surveys the white expanse of tundra and permafrost below.

On the horizon, a long, dark line appears. His plane draws nearer, and the mysterious object reveals itself to be a massive herd of migrating caribou, stretching for miles.

"Seeing those caribou marching single-file across the tundra puts what we're doing here in the Arctic into perspective," says Miller, who is on five-year mission named "CARVE" to study how climate change is affecting the Arctic's carbon cycle.

CARVE is short for the "Carbon in Arctic Reservoirs Vulnerability Experiment."

Now in its third year, the airborne campaign is testing the hypothesis that Arctic carbon reservoirs are vulnerable to warming, while delivering the first source-maps of greenhouse gases carbon dioxide and methane. About two dozen scientists from 12 institutions are participating in this experiment.

"The Arctic is critical to understanding global climate," says Miller. "Climate change is already happening in the Arctic, faster than its ecosystems can adapt. Looking at the Arctic is like looking at the canary in the coal mine for the entire Earth system."

Over hundreds of millennia, Arctic permafrost soils have accumulated vast stores of organic carbon - an estimated 1,400 to 1,850 billion metric tons of it. That's about half of all the estimated organic carbon stored in Earth's soils.

In comparison, about 350 billion metric tons of carbon have been emitted from all fossil-fuel combustion and human activities since 1850. Most of the Arctic's sequestered carbon is located in thaw-vulnerable topsoils within 3 meters of the surface.

But, as scientists are learning, permafrost - and its stored carbon - may not be as permanent as its name implies. And that has them concerned.

"Permafrost soils are warming even faster than Arctic air temperatures - as much as 1.5 to 2.5 degrees Celsius in just the past 30 years," says Miller.

"As heat from Earth's surface penetrates into permafrost, it threatens to mobilize these organic carbon reservoirs and release them into the atmosphere as carbon dioxide and methane, upsetting the Arctic's carbon balance and greatly exacerbating global warming."

Scientists Discover Planet with Diamond Mantle - Twice The Size Of Our Sun

Scientists have announced the discovery of a planet made almost entirely of diamonds.

The planet, called 55 Cancri e, is located in a solar system inside the constellation of Cancer, reports NBC News.

It was discovered in 2004, and scientists have been working since then to determine its mass and radius, as well as study its host star’s composition.

The planet is called a “super-Earth,” and scientists believe that the rocky world is composed mostly of carbon (in the form of either graphite or diamond). It also includes iron, silicon carbide, and possibly silicates.

Scientists also believe, based on their research, that at least one-third of the planet’s mass is pure diamond. Lead researcher Nikku Madhusudhan of Yale University stated:

“This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth. The surface of this planet is likely covered in graphite and diamond rather than water and granite.”

While worlds like the “diamond planet” of 55 Cancri e have been theorized before, and at least one has been discovered before now, it is the first of its kind to be identified orbiting around a sun-like star.

Madhusudhan’s study on the planet was published in the journal Astrophysical Journal Letters.

Princeton University astronomer David Spergel stated that it is relatively easy to find out a star’s basic structure and history once its age and mass have been discovered. He added:

“Planets are much more complex. This ‘diamond-rich super-Earth’ is likely just one example of the rich sets of discoveries that await us as we begin to explore planets around nearby stars.”

The Hazy History of Titan's Air

What rocky moon has a nitrogen-rich atmosphere, Earth-like weather patterns and geology, liquid hydrocarbon seas and a relatively good chance to support life?

The answer is Titan, the fascinating moon of Saturn.

Titan's many similarities to Earth is why astrobiologists are so fascinated by this unusual moon.

Its atmosphere is often viewed as an analog to what the Earth's atmosphere may have been like billions of years ago.

Despite the 800 million miles between the two worlds, both may have had their atmospheres created through the gravitational layering and processing of asteroids and comets.

"Titan provides an extraordinary environment to better understand some of the chemical processes that led to the appearance of life on Earth," says Josep M. Trigo-Rodriguez, of the Institute of Space Sciences (CSIC-IEEC) in Barcelona, Spain.

"Titan's atmosphere is a natural laboratory that, in many aspects, seems to have a strong similitude with our current picture of the pre-biotic atmosphere of Earth."

This is remarkable, because it was thought that Earth and Titan were made from a vastly different recipe of materials in drastically different temperatures, he says.

The research paper, "Clues on the importance of comets in the origin and evolution of the atmospheres of Titan," by Trigo-Rodriguez and F. Javier Martin-Torres (Center for Astrobiology, Madrid, Spain), recently published in the journal Planetary and Space Science, offers insight into the atmospheric affinities of Earth and Titan.


Building an Atmosphere From Scratch
Earth presumably formed from scorched, oxygen-poor rocks (planetesimals) located in the inner solar system, while Titan formed from rocks that were rich in oxygen and other volatile chemicals (cometesimals) in the outer solar system.

Trigo-Rodriguez and Martin-Torres believe the vital organic ingredients in the early Earth's atmosphere were vaporized and swept away by solar winds.

The ingredients for the air we breathe today returned about 4 billion years ago, during a cataclysmic rock storm known as the Late Heavy Bombardment (LHB). During this period, oxygen- and volatile-rich materials from the outer solar system were hurled en masse towards the inner solar system.

Chris McKay, a planetary scientist at NASA's Ames Research Center, says comets may have made small contributions to the water, carbon dioxide, and nitrogen content of the Earth's early atmosphere, "but they were not the main source."

This is known because the Deuterium/Hydrogen ratios of our oceans do not match the ratios found in comets. He says asteroids hurled our way during the LHB could be the main source of water on Earth.

Trigo-Rodriguez says he and McKay are basically on the same page. "We think that asteroids and comets were key sources for water and organics," says Trigo-Rodriguez. Four billion years ago, some asteroids contained so much ice that they would have brought just as much water to our planet as comets did.

Trigo-Rodriguez and Martin Torres studied how hydrogen, carbon, nitrogen and oxygen isotopes reacted with their environments on Earth and Titan. They looked at data recorded by the Cassini-Huygens probe to better understand the isotopic ratios in Titan's dense, hazy atmosphere.

Different distances from the Sun, different sizes and different environmental conditions led to different chemical evolutions on the two worlds. Even so, both Earth and Titan were hit by similar water-rich bodies, which provided a volatile-rich source for both atmospheres during the late-heavy bombardment.

Outgassing and collisional processing on both worlds led to the production of molecular nitrogen-dominated atmospheres with similar isotopic ratios of hydrogen, carbon, nitrogen and oxygen.

Scottish Scientists step towards bringing life to inorganic matter

All life on Earth is carbon-based, which has led to the widespread assumption that any other life that may exist in the universe would also be carbon-based.

Excluding the possibility of elements other than carbon forming the basis of life is often referred to as carbon chauvinism.

Researchers at the University of Glasgow are looking to overcome this bias and provide new insights into evolution by attempting to create “life” from carbon-free, inorganic chemicals.

They’ve now taken the first tentative steps towards this goal with the creation of inorganic-chemical-cells, or iCHELLS.

Prof Cronin says the current theory of evolution is really a special theory of evolution because it only applies only to organic biology. He says that if he and his team are successful in creating life from inorganic matter, it could lead to a general theory of evolution.

"The grand aim is to construct complex chemical cells with life-like properties that could help us understand how life emerged and also to use this approach to define a new technology based upon evolution in the material world - a kind of inorganic living technology," said Prof Cronin.

"If successful this would give us some incredible insights into evolution and show that it's not just a biological process.

It would also mean that we would have proven that non carbon-based life could exist and totally redefine our ideas of design."



Prof Cronin gave a talk at TED Global earlier this year in Edinburgh where he said that if his team is successful in creating life while taking carbon out of the equation, it might reveal what other elements might be capable of producing life elsewhere in the universe and provide NASA with a better idea of what to look for in the search for extraterrestrial life.

The University of Glasgow team's paper "Modular Redox-Active Inorganic Chemical Cells: iCHELLs' is published in the journal Angewandte Chemie.

One box of Girl Scout cookies worth $15 billion - YouTube

In a paper published in the journal ACS Nano, scientists  described how graphene, a single-atom-thick sheet of carbon, can be made from just about any carbon source, including food, insects, and waste.

Read the original study: DOI: 10.1021/nn202625c

“I said we could grow it from any carbon source, for example, a Girl Scout cookie, because Girl Scout cookies were being served at the time,” says James Tour, professor of mechanical engineering and materials science and of computer science at Rice University. “So one of the people in the room said, ‘Yes, please do it. … Let’s see that happen.’”

A sheet of graphene is so thin that one sheet made from one box of shortbread cookies would cover nearly three football fields.

The scientists say the experiment is a whimsical way to make a serious point: that graphene, touted as a miracle material for its toughness and conductivity since its discovery in 2004, can be drawn from many sources.

Tour and graduate students Gedeng Ruan, lead author of the paper, and Zhengzong Sun, also tested other materials, including chocolate, grass, polystyrene plastic, insects (a cockroach leg) and even dog faeces.

In every case, the researchers were able to make high-quality graphene via carbon deposition on copper foil.

In this process, the graphene forms on the opposite side of the foil as solid carbon sources decompose; the other residues are left on the original side. Typically, this happens in about 15 minutes in a furnace flowing with argon and hydrogen gas and turned up to 1,050 degrees Celsius.

Tour expects the cost of graphene to drop quickly as commercial interests develop methods to manufacture it in bulk. In earlier research, Tour  described a long-sought way to make graphene-based transparent electrodes by combining graphene with a fine aluminum mesh.

The material could possibly replace expensive indium tin oxide as a basic element in flat-panel and touch-screen displays, solar cells, and LED lighting.

The new findings have “a lot to do with current research topics in academia and in industry,” Tour says. “Carbon—or any element—in one form can be inexpensive and in another form can be very expensive.”

Diamonds are a good example., he says. “You could probably get a very large diamond out of a box of Girl Scout cookies.”

Sandia National Laboratory, the Air Force Office of Scientific Research, and the Office of Naval Research MURI program funded the research.

More news from Rice University: www.media.rice.edu/media/

Emission control: Turning carbon trash into treasure

Emission control: Turning carbon trash into treasure - New Scientist

IT'S LIKE standing at the edge of a giant patchwork quilt. Stretching into the distance are broad bands of bright yellow alternated with patches of delicate white, all beneath a vast glass roof. This greenhouse full of flowers is just one of hundreds that dot the Dutch coast, where row after row of chrysanthemums, orchids and roses are fed carbon dioxide-enriched air, helping them to grow up to 30 per cent faster than normal.

While plenty of commercial greenhouses top up their air with extra CO2, what is unusual about this one is where its CO2 comes from. Until a few years ago, the greenhouse's operators used to burn natural gas for the sole purpose of generating CO2. Today it is piped from a nearby oil refinery. Each year, 400,000 tonnes of CO2 are captured and then piped to around 500 greenhouses between Rotterdam and The Hague, where it is absorbed by the growing plants before they are shipped for sale around the world (see "Cash for carbon").

As governments ramp up their efforts to cut carbon emissions, carbon capture is moving closer to the top of the agenda. The current plan to deal with all of our excess CO2 is to just pump the stuff underground - a kind of landfill for gases. Looking at this carpet of flowers, it is hard not to think that we are going about this in the wrong way. Shouldn't we look to pioneering schemes like the Dutch greenhouses to find ways to recycle the captured CO2 instead?

It turns out that a growing number of researchers, start-ups and even industry giants are also beginning to think like this. And not just for growing flowers; they believe whole cities could one day be built and powered with the help of exhaust fumes.

"It's time we stopped thinking of CO2 solely as a pollutant and viewed it as a valuable resource," says Gabriele Centi, a chemist at the University of Messina, Italy. "With carbon capture and sequestration, we'll essentially have a zero-cost feedstock."