USF researchers: Life-producing phosphorus carried to Earth by meteorites

This is Matthew Pasek, University of South Florida. -  USF/Aimee Blodgett
This is Matthew Pasek, University of South Florida. – USF/Aimee Blodgett

Scientists may not know for certain whether life exists in outer space, but new research from a team of scientists led by a University of South Florida astrobiologist now shows that one key element that produced life on Earth was carried here on meteorites.

In an article published in the new edition of the Proceedings of the National Academies of Sciences, USF Assistant Professor of Geology Matthew Pasek and researchers from the University of Washington and the Edinburg Centre for Carbon Innovation, revealed new findings that explain how the reactive phosphorus that was an essential component for creating the earliest life forms came to Earth.

The scientists found that during the Hadean and Archean eons – the first of the four principal eons of the Earth’s earliest history – the heavy bombardment of meteorites provided reactive phosphorus that when released in water could be incorporated into prebiotic molecules. The scientists documented the phosphorus in early Archean limestone, showing it was abundant some 3.5 billion years ago.

The scientists concluded that the meteorites delivered phosphorus in minerals that are not seen on the surface of the earth, and these minerals corroded in water to release phosphorus in a form seen only on the early earth.

The discovery answers one of the key questions for scientists trying to unlock the processes that gave rise to early life forms: Why don’t we see new life forms today?

“Meteorite phosphorus may have been a fuel that provided the energy and phosphorus necessary for the onset of life,” said Pasek, who studies the chemical composition of space and how it might have contributed to the origins of life. “If this meteoritic phosphorus is added to simple organic compounds, it can generate phosphorus biomolecules identical to those seen in life today.”

Pasek said the research provides a plausible answer: The conditions under which life arose on the earth billions of years ago are no longer present today.

“The present research shows that this is indeed the case: Phosphorus chemistry on the early earth was substantially different billions of years ago than it is today,” he added.

The research team reached their conclusion after examining earth core samples from Australia, Zimbabwe, West Virginia, Wyoming and in Avon Park, Florida

Previous research had showed that before the emergence of modern DNA-RNA-protein life that is known today, the earliest biological forms evolved from RNA alone. What has stumped scientists, however, was understanding how those early RNA -based life forms synthesized environmental phosphorus, which in its current form is relatively insoluble and unreactive.

Meteorites would have provided reactive phosphorus in the form of the iron-nickel phosphide mineral schreibersite, which in water released soluble and reactive phosphite. Phosphite is the salt scientists believe could have been incorporated into prebiotic molecules.

Of all of the samples analyzed, only the oldest, the Coonterunah carbonate samples from the early Archean of Australia, showed the presence of phosphite, Other natural sources of phosphite include lightning strikes, geothermal fluids and possibly microbial activity under extremely anaerobic condition, but no other terrestrial sources of phosphite have been identified and none could have produced the quantities of phosphite needed to be dissolved in early Earth oceans that gave rise to life, the researchers concluded.

The scientists said meteorite phosphite would have been abundant enough to adjust the chemistry of the oceans, with its chemical signature later becoming trapped in marine carbonate where it was preserved.

It is still possible, the researchers noted, that other natural sources of phosphite could be identified, such as in hydrothermal systems. While that might lead to reducing the total meteoric mass necessary to provide enough phosphite, the researchers said more work would need to be done to determine the exact contribution of separate sources to what they are certain was an essential ingredient to early life.

Comprehensive analysis of impact spherules supports theory of cosmic impact 12,800 years ago

This is UCSB Earth Sciences professor emeritus James Kennett. -  Courtesy photo
This is UCSB Earth Sciences professor emeritus James Kennett. – Courtesy photo

About 12,800 years ago when the Earth was warming and emerging from the last ice age, a dramatic and anomalous event occurred that abruptly reversed climatic conditions back to near-glacial state. According to James Kennett, UC Santa Barbara emeritus professor in earth sciences, this climate switch fundamentally — and remarkably — occurred in only one year, heralding the onset of the Younger Dryas cool episode.

The cause of this cooling has been much debated, especially because it closely coincided with the abrupt extinction of the majority of the large animals then inhabiting the Americas, as well as the disappearance of the prehistoric Clovis culture, known for its big game hunting.

“What then did cause the extinction of most of these big animals, including mammoths, mastodons, giant ground sloths, American camel and horse, and saber- toothed cats?” asked Kennett, pointing to Charles Darwin’s 1845 assessment of the significance of climate change. “Did these extinctions result from human overkill, climatic change or some catastrophic event?” The long debate that has followed, Kennett noted, has recently been stimulated by a growing body of evidence in support of a theory that a major cosmic impact event was involved, a theory proposed by the scientific team that includes Kennett himself.

Now, in one of the most comprehensive related investigations ever, the group has documented a wide distribution of microspherules widely distributed in a layer over 50 million square kilometers on four continents, including North America, including Arlington Canyon on Santa Rosa Island in the Channel Islands. This layer — the Younger Dryas Boundary (YDB) layer — also contains peak abundances of other exotic materials, including nanodiamonds and other unusual forms of carbon such as fullerenes, as well as melt-glass and iridium. This new evidence in support of the cosmic impact theory appeared recently in a paper in the Proceedings of the National Academy of the Sciences.

This cosmic impact, said Kennett, caused major environmental degradation over wide areas through numerous processes that include continent-wide wildfires and a major increase in atmospheric dust load that blocked the sun long enough to cause starvation of larger animals.

Investigating 18 sites across North America, Europe and the Middle East, Kennett and 28 colleagues from 24 institutions analyzed the spherules, tiny spheres formed by the high temperature melting of rocks and soils that then cooled or quenched rapidly in the atmosphere. The process results from enormous heat and pressures in blasts generated by the cosmic impact, somewhat similar to those produced during atomic explosions, Kennett explained.

But spherules do not form from cosmic collisions alone. Volcanic activity, lightning strikes, and coal seam fires all can create the tiny spheres. So to differentiate between impact spherules and those formed by other processes, the research team utilized scanning electron microscopy and energy dispersive spectrometry on nearly 700 spherule samples collected from the YDB layer. The YDB layer also corresponds with the end of the Clovis age, and is commonly associated with other features such as an overlying “black mat” — a thin, dark carbon-rich sedimentary layer — as well as the youngest known Clovis archeological material and megafaunal remains, and abundant charcoal that indicates massive biomass burning resulting from impact.

The results, according to Kennett, are compelling. Examinations of the YDB spherules revealed that while they are consistent with the type of sediment found on the surface of the earth in their areas at the time of impact, they are geochemically dissimilar from volcanic materials. Tests on their remanent magnetism — the remaining magnetism after the removal of an electric or magnetic influence — also demonstrated that the spherules could not have formed naturally during lightning strikes.

“Because requisite formation temperatures for the impact spherules are greater than 2,200 degrees Celsius, this finding precludes all but a high temperature cosmic impact event as a natural formation mechanism for melted silica and other minerals,” Kennett explained. Experiments by the group have for the first time demonstrated that silica-rich spherules can also form through high temperature incineration of plants, such as oaks, pines, and reeds, because these are known to contain biologically formed silica.

Additionally, according to the study, the surface textures of these spherules are consistent with high temperatures and high-velocity impacts, and they are often fused to other spherules. An estimated 10 million metric tons of impact spherules were deposited across nine countries in the four continents studied. However, the true breadth of the YDB strewnfield is unknown, indicating an impact of major proportions.

“Based on geochemical measurements and morphological observations, this paper offers compelling evidence to reject alternate hypotheses that YDB spherules formed by volcanic or human activity; from the ongoing natural accumulation of space dust; lightning strikes; or by slow geochemical accumulation in sediments,” said Kennett.

“This evidence continues to point to a major cosmic impact as the primary cause for the tragic loss of nearly all of the remarkable American large animals that had survived the stresses of many ice age periods only to be knocked out quite recently by this catastrophic event.”

A sprightly explanation for UFO sightings?

The appearance of a 'sprite' (about 30 miles high by 30 miles wide), flashing above a distant thunderstorm. The 'sprite' is about 175-250 miles away from the camera. -  ILAN Science Team
The appearance of a ‘sprite’ (about 30 miles high by 30 miles wide), flashing above a distant thunderstorm. The ‘sprite’ is about 175-250 miles away from the camera. – ILAN Science Team

In legend, sprites are trolls, elves and other spirits that dance high above our ozone layer. But scientists at Tel Aviv University have discovered that some very real “sprites” are zipping across the atmosphere as well, providing a possible explanation for those other legendary denizens of the skies, UFOs.

Thunderstorms, says Prof. Colin Price, head of the Geophysics and Planetary Sciences Department at Tel Aviv University, are the catalyst for a newly discovered natural phenomenon he calls “sprites.” He and his colleagues are one of the leading teams in the world studying the phenomenon, and Prof. Price leads the study of “winter sprites” ― those that appear only in the northern hemisphere’s winter months.

“Sprites appear above most thunderstorms,” explains Prof. Price, “but we didn’t see them until recently. They are high in the sky and last for only a fraction of a second.” While there is much debate over the cause or function of these mysterious flashes in the sky, they may, Prof. Price says, explain some bizarre reports of UFO sightings.

An Electrifying Discovery

Sprites are described as flashes high in the atmosphere, between 35 and 80 miles from the ground, much higher than the 7 to 10 miles where regular lightning bolts usually occur.

“Lightning from the thunderstorm excites the electric field above, producing a flash of light called a sprite,” explains Prof. Price. “We now understand that only a specific type of lightning is the trigger that initiates sprites aloft.”

Though sprites have existed for millions of years, they were first discovered and documented only by accident in 1989 when a researcher studying stars was calibrating a camera pointed at the distant atmosphere where sprites occur.

“Sprites, which only occur in conjunction with thunderstorms, never occur on their own, and are cousins to similar natural phenomenon dubbed by atmospheric electricians as ‘elves,’ ‘goblins’ and ‘trolls,'” Prof. Price says. These flashes are so named because they appear to “dance” in the sky, which may explain some UFO sightings.

Candles on a Celestial Birthday Cake

Tel Aviv University’s research team is one of the leading global groups studying the phenomenon. But Prof. Price and his students are now working in collaboration with other Israeli scientists from The Open University and The Hebrew University to take three-dimensional pictures of sprites to gain a better understanding of their structure. Using remote-controlled roof-mounted cameras, the researchers are able to look at the thunderstorms that produce sprites when they are still over the Mediterranean Sea.

From their unique vantage point in Israel, the researchers are leading the world in the study of winter sprites. Prof. Price’s new camera techniques, in particular, have revealed the sprites’ circular structures, which are much like those of candles on a birthday cake. Using triangulation, Prof. Price and his team have also been able to calculate the dimensions of the sprites’ features. “The candles in the sprites are up to 15 miles high, with the cluster of candles 45 miles wide — it looks like a huge birthday celebration!”

Because of their high altitude, sprites may also have an impact on the chemistry of the Earth’s ozone layer. “Since they are relatively infrequent, the global impact is likely small,” says Prof. Price. “But we’re researching that now.”