**Science Thread**

[marcus300]

Study: Simple Life Forms are Common throughout Universe

A detailed analysis of 3.465-billion-year-old microbial microfossils provides evidence to support an increasingly widespread understanding that life in the Universe is common.

.465-billion-year-old fossil microbes indicate that life in the Universe is common. Image credit: Reimund Bertrams
Professor J. William Schopf from the University of California, Los Angeles, and his colleagues analyzed 11 specimens of 5 species of prokaryotic cellular microfossils from the Apex Basalt Formation, Pilbara Craton, Western Australia.

Two of the five species the researchers studied were primitive photosynthesizers, one was an Archaeal methane producer, and two others were methane consumers.

“The evidence that a diverse group of organisms had already evolved extremely early in the Earth’s history strengthens the case for life existing elsewhere in the Universe because it would be extremely unlikely that life formed quickly on Earth but did not arise anywhere else,” they said.

The study, published in the Proceedings of the National Academy of Sciences, is the most detailed ever conducted on microorganisms preserved in such ancient fossils.

A 3.465-billion-year-old fossil microorganism from Western Australia. Image credit: J. William Schopf / Center for the Study of Evolution and the Origin of Life, University of California, Los Angeles.
“By 3.465 billion years ago, life was already diverse on Earth; that’s clear — primitive photosynthesizers, methane producers, methane users,” Professor Schopf said.

“These are the first data that show the very diverse organisms at that time in Earth’s history, and our previous research has shown that there were sulfur users 3.4 billion years ago as well.”

“This tells us life had to have begun substantially earlier and it confirms that it was not difficult for primitive life to form and to evolve into more advanced microorganisms.”

“Scientists still do not know how much earlier life might have begun. But, if the conditions are right, it looks like life in the Universe should be widespread.”

A methane-consuming fossil microorganism from Western Australia. Image credit: J. William Schopf / Center for the Study of Evolution and the Origin of Life, University of California, Los Angeles.

Professor Schopf and co-authors analyzed the Apex specimens with cutting-edge technology called secondary ion mass spectroscopy (SIMS), which reveals the ratio of carbon-12 to carbon-13 isotopes — information scientists can use to determine how the microorganisms lived.

They used a secondary ion mass spectrometer — one of just a few in the world — to separate the carbon from each fossil into its constituent isotopes and determine their ratios.

“The differences in carbon isotope ratios correlate with their shapes. Their carbon-12 to carbon-13 ratios are characteristic of biology and metabolic function,” said co-author Professor John Valley, from the University of Wisconsin, Madison.

“The fossils were formed at a time when there was very little oxygen in the atmosphere,” Professor Schopf added.

“I think that advanced photosynthesis had not yet evolved, and that oxygen first appeared on Earth approximately half a billion years later before its concentration in our atmosphere increased rapidly starting about 2 billion years ago.”

“Oxygen would have been poisonous to these microorganisms, and would have killed them,” the scientist said.

Primitive photosynthesizers are fairly rare on Earth today because they exist only in places where there is light but no oxygen — normally there is abundant oxygen anywhere there is light.

And the existence of the rocks the team analyzed is also rather remarkable.

“The average lifetime of a rock exposed on the surface of the Earth is about 200 million years,” Professor Schopf noted.

“When I began my career, there was no fossil evidence of life dating back farther than 500 million years ago. The rocks we studied are about as far back as rocks go.”

“While the study strongly suggests the presence of primitive life forms throughout the Universe, the presence of more advanced life is very possible but less certain,” he said.

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J. William Schopf et al. SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions. PNAS, published online December 18, 2017; doi: 10.1073/pnas.1718063115

[marcus300]

ESA Releases Stunning New Image of Mars
In this stunning image taken by ESA’s Mars Express spacecraft, Mars is seen with north at the bottom, and the equator at the top.


A stunning view of Mars from the north pole to the equator. Image credit: ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO.

The image was taken on June 19, 2017, for calibrating Mars Express’ High Resolution Stereo Camera (HRSC), while the spacecraft was flying from north to south.

HRSC’s nine channels — one nadir (downward-pointing), four color and four stereo — panned over the Martian surface to record a large area with the same illumination conditions. At the same time, HRSC was shifted to the horizon, instead of just pointing to the surface as in routine imaging.

The result is this wide-angle view of the Red Planet, with the illuminated horizon near the equator at the top of the image, and the shadowed north pole at the bottom.

“The northern polar cap was composed of water ice and dust at the time of imaging, at the beginning of spring,” Mars Express scientists said.

“The carbon dioxide ice present in winter had already evaporated from the solid form to a gas. Similarly, water-ice also evaporates, injecting a large amount of water into the atmosphere that is circulated to the south by atmospheric motions. When the seasons change back, carbon dioxide frost and water-ice build up again.”

This map shows the context of the above image outlined by the large highlighted central swath, and the topography of the region. The colors relate to the elevation of the landscape: purple and blue are the lowest and red/brown/white are the highest (values are marked on the scale at bottom left). In this map, north is at the bottom, and south is towards the top. The map is based on data from the Mars Orbiter Laser Altimeter of NASA’s Mars Global Surveyor. Image credit: NASA / MGS / MOLA Science Team / FU Berlin.

Panning south, the view soaks up sights of some of the planet’s largest volcanoes in the Tharsis region.

The region covers an area larger than Europe, and rises some 3.1 miles (5 km) above the planet’s average elevation, with volcanoes towering 6.2-13.7 miles (10-22 km) in height.

Olympus Mons, the largest volcano on Mars and in the Solar System, is out of view in the scene, leaving a vast shield volcano called Alba Mons to take center stage in the top half of the image.

“Alba Mons lies at the edge of the Tharsis uplift, and a number of parallel linear features can be seen around it, their formation tied to the tectonic stresses of the Tharsis bulge,” the researchers said.

“As this region swelled with magma in the planet’s first billion years of history the crust was stretched apart. Later, when subsurface magma chambers were discharged, subsidence of the crust also generated fractures.”

Further towards the horizon, the 9.3-mile (15 km) high Ascraeus Mons comes into view, on this occasion covered by hazy clouds. Thin layers of clouds can also be seen several tens of miles above the horizon.

Other volcanoes can also be seen to the left of Ascraeus Mons, including Uranius Mons, Ceraunius Tholus and Tharsis Tholus.

[marcus300]

Astronomers Obtain Images of Near-Earth Asteroid Phaethon

A sequence of radar images of the near-Earth asteroid (3200) Phaethon was obtained in December 2017 by astronomers using the NASA-funded planetary radar system at NSF’s Arecibo Observatory in Puerto Rico, when the asteroid was about 1.1 million miles (1.8 million km) from our planet.

These colorized radar images show the near-Earth asteroid Phaethon. At time of closest approach on December 16, 2017, Phaethon was about 1.1 million miles (1.8 million km) away. The encounter is the closest the asteroid will come to Earth until 2093. Image credit: Arecibo Observatory / NASA / NSF

Phaethon was discovered on October 11, 1983, by NASA’s Infrared Astronomical Satellite (IRAS).

This asteroid is the parent body of the Geminid meteor shower of mid-December.

It is categorized as a so-called Apollo asteroid, as its orbital semi-major axis is greater than that of the Earth’s at 118 million miles (190 million km, or 1.27 AU).

The new observations of Phaethon were conducted at the Arecibo Observatory from December 15 through 19, 2017.

The radar images reveal Phaethon, which made its closest approach on December 16 at 6 p.m. EST (3 p.m. PST, 11 p.m. UTC) at a distance of about 1.1 million miles (1.8 million km, or about 4.6 times the distance from Earth to the Moon), is spheroidal in shape.

The object has a large concavity, or depression, at least several hundred feet in extent near its equator, and a conspicuous dark, circular feature near one of the poles.

“These new observations of Phaethon show it may be similar in shape to asteroid Bennu, the target of NASA’s OSIRIS-REx spacecraft, but more than 1,000 Bennus could fit inside of Phaethon,” said Dr. Patrick Taylor, a scientist at the Universities Space Research Association and group leader for the planetary radar at Arecibo.

“The dark feature could be a crater or some other topographic depression that did not reflect the radar beam back to Earth.”

The radar images also indicate Phaethon has a diameter of about 3.6 miles (6 km) — roughly 0.6 miles (1 km) larger than previous estimates.

“Arecibo is an important global asset, crucial for planetary defense work because of its unique capabilities,” said Dr. Joan Schmelz, deputy director of Arecibo Observatory and a scientist at the Universities Space Research Association.

“We have been working diligently to get it back up and running since Hurricane Maria devastated Puerto Rico.”

[marcus300]

2,000-Year-Old Petroglyphs Mapped in Venezuela

Dr. Philip Riris from the Institute of Archaeology at University College London and colleagues have mapped a series of rock engravings (petroglyphs), some of which are thought to be up to 2,000 years old, in the Amazonas state of Venezuela



Aerial photograph of monumental Cerro Pintado petroglyphs. Image credit: Philip Riris, doi: 10.15184/aqy.2017.152.

The Venezuelan petroglyphs are located in the Atures Rapids area of the Amazonas state, historically reported as the home of the native Adoles by Jesuit priests.

They include depictions of animals, humans and cultural rituals.

One panel is 304 m2 containing at least 93 individual engravings, the largest of which measure several feet across. Another engraving of a horned snake measures more than 100 feet (30 m) in length.

Dr. Riris and co-authors used drones to photograph the petroglyph, some of which are in highly inaccessible areas.


Oblique aerial view of western panel on Picure, with interpretative overlay of main engravings. Image credit: Philip Riris, doi: 10.15184/aqy.2017.152.

“The Rapids are an ethnic, linguistic and cultural convergence zone,” Dr. Riris said.

“The motifs documented here display similarities to several other rock art sites in the locality, as well as in Brazil, Colombia, and much further afield.”

“This is one of the first in-depth studies to show the extent and depth of cultural connections to other areas of northern South America in pre-Columbian and Colonial times.”

“The size of some of the individual engravings is quite extraordinary.”

Almost all of the engravings found in the Rapids are inundated and exposed to varying degrees by seasonally rising and falling water levels in the Orinoco River.

Depending on fluctuating upstream precipitation, the relative height of the river also varies annually by up to several feet during the extremes of both seasons.



Six human figures on the western panel of Picure, including a flautist. Inset: polynomial texture mapping detail of flautist. Image credit: Philip Riris, doi: 10.15184/aqy.2017.152.

“In one panel surveyed, a motif of a flautist surrounded by other human figures probably depicts part of an indigenous rite of renewal,” the researchers said.

“Performances conceivably coincided with the seasonal emergence of the engravings from the river just before the onset of the wet season, when the islands are more accessible and the harvest would take place.”

“Mapping the rock engravings represents a major step towards an enhanced understanding of the role of the Orinoco River in mediating the formation of pre-Conquest social networks throughout northern South America,” added team member Dr. José Oliver, also from the Institute of Archaeology at University College London.

The results of this research are published in the journal Antiquity.

_____

Philip Riris. 2017. On confluence and contestation in the Orinoco interaction sphere: the engraved rock art of the Atures Rapids. Antiquity 91 (360): 1603-1619; doi: 10.15184/aqy.2017.152

[cousinmuscles]

New LiDAR technology reveals ancient Mayan city was much larger than previously believed; estimates at 10-20 million population. The images reveal very large farming areas with irrigation channels made to support such a population and roads at heightened areas to be functional during any weather conditions.

https://www.sciencealert.com/guatema...-for-centuries