Meteorites yield clues to Martian early atmosphere - Sulphur

A microscope reveals colorful augite crystals in this 1.3 billion-year-old meteorite from Mars, which researchers studied to understand the red planet's atmospheric history. 

Credit: James Day

Geologists who analyzed 40 meteorites that fell to Earth from Mars unlocked secrets of the Martian atmosphere hidden in the chemical signatures of these ancient rocks.

Their study, published April 17 in the journal Nature, shows that the atmospheres of Mars and Earth diverged in important ways very early in the 4.6 billion year evolution of our solar system.

The results will help guide researchers' next steps in understanding whether life exists, or has ever existed, on Mars and how water—now absent from the Martian surface—flowed there in the past.

Heather Franz

Heather Franz, a former University of Maryland (UMD) research associate who now works on the Curiosity rover science team at the NASA Goddard Space Flight Center, led the study with James Farquhar, co-author and UMD geology professor.

The researchers measured the sulfur composition of 40 Mars meteorites—a much larger number than in previous analyses. Of more than 60,000 meteorites found on Earth, only 69 are believed to be pieces of rocks blasted off the Martian surface.

The meteorites are igneous rocks that formed on Mars, were ejected into space when an asteroid or comet slammed into the red planet, and landed on Earth.

James Farquhar

The oldest meteorite in the study is about 4.1 billion years old, formed when our solar system was in its infancy. The youngest are between 200 million and 500 million years old.

Studying Martian meteorites of different ages can help scientists investigate the chemical composition of the Martian atmosphere throughout history, and learn whether the planet has ever been hospitable to life.

Mars and Earth share the basic elements for life, but conditions on Mars are much less favourable, marked by an arid surface, cold temperatures, radioactive cosmic rays, and ultraviolet radiation from the Sun.

Still, some Martian geological features were evidently formed by water – a sign of milder conditions in the past.

Scientists are not sure what conditions made it possible for liquid water to exist on the surface, but greenhouse gases released by volcanoes likely played a role.

Sulphur, which is plentiful on Mars, may have been among the greenhouse gases that warmed the surface, and could have provided a food source for microbes.

Because meteorites are a rich source of information about Martian sulphur, the researchers analyzed sulfur atoms that were incorporated into the rocks.

In the Martian meteorites, some sulphur came from molten rock, or magma, which came to the surface during volcanic eruptions.

Volcanoes also vented sulphur dioxide into the atmosphere, where it interacted with light, reacted with other molecules, and settled on the surface.

The team's work has yielded the most comprehensive record of the distribution of sulphur isotopes on Mars.

In effect, they have compiled a database of atomic fingerprints that provide a standard of comparison for sulphur-containing samples collected by NASA's Curiosity rover and future Mars missions.

This information will make it much easier for researchers to zero in on any signs of biologically produced sulphur, Farquhar said.

More information: Isotopic links between atmospheric chemistry and the deep sulphur cycle on Mars, Nature, DOI: 10.1038/nature13175

New improved view of supernova explosion and death throes

Three-dimensional turbulent mixing in a stratified burning oxygen shell which is four pressure scale heights deep. 

The yellow ashes of sulphur are being dredged up from the underlying orange core. 

The multi-scale structure of the turbulence is prominent. 

Entrained material is not particularly well mixed, but has features which trace the large scale advective flows in the convection zone. 

Also visible are smaller scale features, which are generated as the larger features become unstable, breaking apart to become part of the turbulent cascade. 

The white lines indicate the boundary of the computational domain. 

Credit: Arnett, Meakin and Viallet/AIP Advances

A powerful, new three-dimensional model provides fresh insight into the turbulent death throes of supernovas, whose final explosions outshine entire galaxies and populate the universe with elements that make life on Earth possible.

W. David Arnett

The model is the first to represent the start of a supernova collapse in three dimensions, said its developer, W. David Arnett, Regents Professor of Astrophysics at the University of Arizona, who developed the model with Casey Meakin and Nathan Smith at Arizona and Maxime Viallet of the Max-Planck Institut fur Astrophysik.

Described in the journal AIP Advances, it shows how the turbulent mixing of elements inside stars causes them to expand, contract, and spit out matter before they finally detonate.

Arnett, a pioneer in building models of physical processes inside stars, traces his fascination with turbulence to 1987A, the first supernova of 1987.

Located in a nearby galaxy, it was bright enough to see with the naked eye.

The star puzzled astronomers, Arnett recalled, because the material ejected by its explosion appeared to mix with material previously ejected from the star.

Existing models could not explain that. "Instead of going gently into that dark night, it is fighting. It is sputtering and spitting off material. This can take a year or two. There are small precursor events, several peaks, and then the big explosion.

"Perhaps what we need is a more sophisticated notion of what an explosion is, to explain what we are seeing," Arnett concludes.

More information: The article, "Chaos and turbulent nucleosynthesis prior to a supernova explosion" by David Arnett, Casey Meakin and Maxime Viallet appears in the journal AIP Advances (DOI: 10.1063/1.4867384). 

The article will be published online on March 18, 2014. dx.doi.org/10.1063/1.4867384

Windows Into Jupiter's moon Europa's Interior

This graphic of Jupiter's moon Europa maps a relationship between the amount of energy deposited onto the moon from charged-particle bombardment and the chemical contents of ice deposits on the surface in five areas of the moon (labeled A through E). 

Credit: NASA/JPL-Caltech/Univ. of Ariz./JHUAPL/Univ. of Colo.

The surface of Jupiter's moon Europa exposes material churned up from inside the moon and also material resulting from matter and energy coming from above.

If you want to learn about the deep saltwater ocean beneath this unusual world's icy shell -- as many people do, certainly those who are interested in possible extraterrestrial life -- you might target your investigation of the surface.

New analysis of observations made more than a decade ago by NASA's Galileo mission to Jupiter helps identify the deposits that have emanated from 'below' the surface rather than those deposited 'on' the surface.

In particular the report examines Sulphuric Acid Hydrate production on Europa's surface.

J. Brad Dalton

"We have found the regions where charged electrons and ions striking the surface would have done the most, and the least, chemical processing of materials emplaced at the surface from the interior ocean," said J. Brad Dalton of NASA's Jet Propulsion Laboratory, Pasadena, Calif., lead author of the report published recently in the journal Planetary and Space Science.

"That tells us where to look for materials representing the most pristine ocean composition, which would be the best places to target with a lander or study with an orbiter."

Europa is about the size of Earth's moon and, like our moon, keeps the same side toward the planet it orbits.

Picture a car driving in circles around a mountain with its left-side windows always facing the mountain.

Europa's orbit around Jupiter is filled with charged, energetic particles tied to Jupiter's powerful magnetic field.

Jupiter's Moon Io

Besides electrons, these particles include ions of sulphur and oxygen originating from volcanic eruptions on Io, a neighbouring Jupiter moon.

The magnetic field carrying these energetic particles sweeps around Jupiter faster than Europa orbits Jupiter, in the same direction: about 10 hours per circuit for the magnetic field versus about 3.6 days for Europa's orbit.

So, instead of our mountain-circling car getting bugs on the front windshield, the bugs are plastered on the back of the car by a "wind" from behind going nearly nine times faster than the car.

Europa has a "leading hemisphere" in front and a "trailing hemisphere" in back.

NASA's Galileo Satellite

Earlier studies had found more sulphuric acid hydrate being produced towards the center of the trailing hemisphere than elsewhere on Europa's surface, interpreted as resulting from chemistry driven by sulphur ions bombarding the icy surface.

Surface deposits in these areas are most likely to preserve the original chemical compounds that erupted from the interior.

Dalton suggests that any future spacecraft missions to Europa should target these deposits for study from orbit, or even attempt to land there.

Dalton stated "While investigating the products of surface chemistry driven by charged particles is still interesting from a scientific standpoint, there is a strong push within the community to characterize the contents of the ocean and determine whether it could support life. These kinds of places just might be the windows that allow us to do that."

Dallol - The World's Weirdest Volcanic Crater - Images

In the North East of Ethiopia lies the Danokil Desert. At its heart is a volcanic crater, Dallol, little known and seldom visited but quite extraordinary.

Surrounding the volcano are acidic hot springs, mountains of sulphur, pillars of salt, small gas geysers and pools of acid isolated by salt ridges. It makes for one of the most bizarre landscapes on planet Earth.

Dallol - The World's Weirdest Volcanic Crater ~ Kuriositas

Mars Rover Opportunity: Rich Vein Of Gypsum Water Deposits

This colour view of a mineral vein called "Homestake" comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity.

The vein is about the width of a thumb and about 18 inches (45 centimeters) long.

Opportunity examined it in November 2011 and found it to be rich in calcium and sulphur, possibly the calcium-sulphate mineral gypsum. Homestake is near the edge of the "Cape York" segment of the western rim of Endeavour Crater.

Exposures combined into this view were taken through Pancam filters admitting light with wavelengths centered at 601 nanometers (red), 535 nanometers (green) and 482 nanometers (blue).

The view is presented in approximate true colour. This "natural colour" is the rover team's best estimate of what the scene would look like if humans were there and able to see it with their own eyes.

The exposures were taken during the 2,769th Martian day, or sol, of Opportunity's career on Mars (Nov. 7, 2011).

World's smallest electric motor made from single molecule

Chemists at Tufts University have developed the world's first single molecule electric motor, which may potentially create a new class of devices that could be used in applications ranging from medicine to engineering.

The molecular motor was powered by electricity from a state of the art, low-temperature scanning tunneling microscope.

This microscope sent an electrical current through the molecule, directing the molecule to rotate in one direction or another.

The molecule had a sulphur base (yellow); when placed on a conductive slab of copper (orange), it became anchored to the surface.

The sulphur-containing molecule had carbon and hydrogen atoms radiating off to form what looks like two arms (gray); these carbon chains were free to rotate around the central sulphur-copper bond.

The researchers found that reducing the temperature of the molecule to five Kelvin (K), or about minus 450 degrees Fahrenheit (ºF), enabled them to precisely impact the direction and rotational speed of the molecular motor

The Tufts team plans to submit this miniature electric motor to the Guinness World Records. The research was published online Sept. 4 in Nature Nanotechnology.

Credit: Heather L. Tierney, Colin J. Murphy, April D. Jewell, Ashleigh E. Baber, Erin V. Iski, Harout Y. Khodaverdian, Allister F. McGuire, Nikolai Klebanov and E. Charles H. Sykes.

HiRISE | Sulphates in Ius Chasma

HiRISE | Sulphates in Ius Chasma

Missing link found in the biology of cloud formation

Scientists have known for two decades that sulphur compounds that are produced by bacterioplankton as they consume decaying algae in the ocean cycle through two paths.

In one, a sulphur compound dimethylsulphide, or DMS, goes into the atmosphere, where it leads to water droplet formation - the basis of clouds that cool the Earth. In the other, a sulphur compound goes into the ocean's food web, where it is eaten and returned to seawater.

What they haven't known is how sulphur is routed one way or the other or why.

They also have wondered what if - in a time of growing concern about global warming - it was possible to divert the sulphur compound that goes into the oceans into the atmosphere, helping to mitigate global warming?

A study by researchers at the University of Georgia just published in Nature brings the possibility of using the sulphur cycle to mitigate global warming closer with the identification of the steps in the biochemical pathway that controls how bacteria release the sulphur compound methanethiol, or MeSH, into the microbial food web in the oceans and the genes responsible for that process.

"With our increased understanding of the sulphur cycle in the ocean," said study co-author William (Barny) Whitman, "we are now better able to evaluate the impacts of climate change on the process and the potential for its manipulation, which has been proposed as a way to mitigate global warming.

"It's wonderful to have this much understanding of a major biogeochemical process," noted Whitman, distinguished research professor and head of the department of microbiology in the Franklin College of Arts and Sciences.

In addition to elucidating the steps in the pathway and identifying the responsible genes, the team of UGA microbiologists, marine scientists and chemists discovered that the pathway is found widely, not only among bacterioplankton in the ocean but also in non-marine environments.

"The big mystery about bacteria is what they are doing in nature," Whitman said. "The organisms metabolise compounds for their own needs. We need to understand what they are getting out of it to understand what it means for the ocean, and now it will be possible to look at the environmental importance of this process and how it's regulated." That will help to answer the "why" of the two sulphur fates.

Co-authors of the Nature paper were UGA graduate students Chris Reisch and Vanessa Varaljay, department of microbiology; graduate student Melissa Stoudemayer and Jon Amster, professor and head, department of chemistry; and distinguished research professor Mary Ann Moran, department of marine sciences-all in the Franklin College of Arts and Sciences.

The collaborators in this study built on a line of research begun at UGA over a decade ago. Moran's early research showed that an abundant group of bacteria known as marine roseobacters play a role in moving dimethylsulphonioproprionate (DMSP), the chemical made by marine algae and released into the water upon their death, into the atmosphere as the compound dimethylsulphide (DMS).

Missing link found in the biology of cloud formation over the oceans

Witch Bottles: Urine, Nails and Magic Spells

A rare insight into the folk beliefs of 17th-century Britons has been gleaned from the analysis of a sealed "witch bottle" unearthed in Greenwich, London, in 2004.

Witch bottles were commonly buried to ward off spells during the late 16th and 17th centuries, but it is very rare to find one still sealed.

"So many have been dug up and their contents washed away down the sink," says Alan Massey, a retired chemist formerly at the University of Loughborough, UK, who has examined so-called "magical" artifacts and was asked to analyse the contents of the bottle. "This is the first one that has been opened scientifically."

During the 17th century, British people often blamed witches for any ill health or misfortune they suffered, says Massey. "The idea of the witch bottle was to throw the spell back on the witch," he says. "The urine and the bulb of the bottle represented the waterworks of the witch, and the theory was that the nails and the bent pins would aggravate the witch when she passed water and torment her so badly that she would take the spell back off you."

The salt-glazed jar was discovered 1.5 metres below ground by archaeologists from The Maritime Trust, a Greenwich-based charity that preserves historic sailing vessels. When it was shaken, the bottle splashed and rattled, and an X-ray showed pins and nails stuck in the neck, suggesting that it had been buried upside down.

Further computed tomography scans showed it to be half-filled with liquid, which later analysis showed to be human urine. The bottle also contained bent nails and pins, a nail-pierced leather "heart", fingernail clippings, navel fluff and hair. The presence of iron sulphide in the mixture also suggests that sulphur or brimstone had been added.

"Prior to this point, all we really knew about what was in witch bottles was what we read from documents from the 17th century," says Brian Hoggard, an independent expert on British witchcraft who helped analyse the bottle. These texts suggest "recipes" for filling a witch bottle, but don't tell us what actually went into them.

Sulphur is not mentioned in any recipe Massey has seen, although a previously discovered bottle seemed to contain the remains of some matches, he says. "If you think about where sulphur came from in those days, it spewed out of volcanic fumaroles from the underworld. It would have been the ideal thing to [kill] your witch, if you wished to."

Demographic distinction of urine analysis

Further analysis of the urine showed that it also contained cotinine, a metabolite of nicotine, suggesting that it came from a smoker, while the nail clippings appear quite manicured, suggesting that a person of some social standing created the bottle.