SoylentNews

Phoenix666 writes:

Nitrogen is one of the essential nutrients of life on Earth, with some organisms, such as the kinds of microbes found within the roots of legume plants, capable of converting nitrogen gas into molecules that other species can use.

Nitrogen fixation, as the process is called, involves breaking the powerful chemical bonds that hold nitrogen atoms in pairs in the atmosphere and using the resulting single nitrogen atoms to help create molecules such as ammonia, which is a building block of many complex organic molecules, such as proteins, DNA and RNA.

With organisms playing such a crucial role in the chemistry of nitrogen on Earth, scientists are examining nitrogen in billion-year-old rocks to decipher its potential as a bio-signature of life on other planets. New findings in this area of research appeared recently in the paper, "Nitrogen in Ancient Mud: A Biosignature?" in the journal Astrobiology.

"This study identifies nitrogen abundances as a potential tool to detect remnants of life on Mars," said one of the study's authors, Eva Stüeken, an astrobiologist at the University of Washington at Seattle and the University of California at Riverside.

Original Submission

takyon writes:

Oxygen ions from Earth are periodically transferred to the lunar surface, according to a new study:

A small bit of Earth's air leaks into space each day. (Don't worry, it's only about 90 metric tons out of a total of about 5 quadrillion metric tons.) Some atoms and molecules near the top of our atmosphere are simply moving so fast they overcome Earth's gravitational tug. Charged particles can be accelerated to even higher speed by our planet's magnetic field. Once these émigrés escape our world, they remain inside a teardrop-shaped region of space surrounding Earth called the magnetosphere (whose rounded end is pointed toward the sun) and are eventually blown away from the sun by the solar wind and into interplanetary space.

For the largest part of each month, the moon is bombarded with high-speed, highly charged atoms spewing from the sun and carried by the solar wind. But for 5 days every month, Earth's magnetosphere passes over the moon, shielding it from the solar particles and allowing slower speed particles from Earth to take their place, says Kentaro Terada, a cosmochemist at Osaka University in Toyonaka, Japan. Moon-orbiting probes experience the same conditions, he notes.

[...] During each burst of oxygen, an estimated 26,000 ions per second passed through each square centimeter of [the Kaguya moon-orbiting probe's] sensor, the researchers say. [...] Those atoms' origin in the ozone layer might also help explain a longstanding mystery about some grains of lunar soil brought back by Apollo astronauts. A few of those grains sport higher-than-normal proportions of oxygen-17 and oxygen-18 isotopes (as compared with the universe's predominant form of the element, oxygen-16). Notably, Terada and his colleagues say, previous studies have shown that the overall proportions of oxygen isotopes in the ozone layer also are skewed toward above-average concentrations of oxygen-17 and oxygen-18.

Biogenic oxygen from Earth transported to the Moon by a wind of magnetospheric ions (open, DOI: 10.1038/s41550-016-0026) (DX)

Original Submission

takyon writes:

Astrophysicists have modeled the effects of red dwarf star flare activity on the atmospheres of orbiting exoplanets, and found that heavy gases including oxygen would be lost quickly, even in the so-called "habitable zone":

[When] the scientists accounted for superflares, their new model indicates the violent storms of young red dwarfs generate enough high-energy radiation to enable the escape of even oxygen and nitrogen – building blocks for life's essential molecules.

"The more X-ray and extreme ultraviolet energy there is, the more electrons are generated and the stronger the ion escape effect becomes," Glocer said. "This effect is very sensitive to the amount of energy the star emits, which means it must play a strong role in determining what is and is not a habitable planet."

Considering oxygen escape alone, the model estimates a young red dwarf could render a close-in exoplanet uninhabitable within a few tens to a hundred million years. The loss of both atmospheric hydrogen and oxygen would reduce and eliminate the planet's water supply before life would have a chance to develop.

"The results of this work could have profound implications for the atmospheric chemistry of these worlds," said Shawn Domagal-Goldman, a Goddard space scientist not involved with the study. "The team's conclusions will impact our ongoing studies of missions that would search for signs of life in the chemical composition of those atmospheres."

The research has obvious implications for exoplanets like Proxima Centauri b.

YouTube video (20 seconds).

How Hospitable Are Space Weather Affected Habitable Zones? The Role of Ion Escape (DOI: 10.3847/2041-8213/836/1/L3) (DX)

Original Submission

takyon writes:

Astronomers have observed enough planetary transits to confirm the existence of seven "Earth-sized" exoplanets orbiting TRAPPIST-1, an ultra-cool (~2550 K) red dwarf star about 39.5 light years away. Three of the exoplanets are located inside the "habitable zone" of their parent star. These three orbit from 0.028 to 0.045 AU away from the star:

Astronomers using the TRAPPIST–South telescope at ESO's La Silla Observatory, the Very Large Telescope (VLT) at Paranal and the NASA Spitzer Space Telescope, as well as other telescopes around the world, have now confirmed the existence of at least seven small planets orbiting the cool red dwarf star TRAPPIST-1. All the planets, labelled TRAPPIST-1b, c, d, e, f, g and h in order of increasing distance from their parent star, have sizes similar to Earth.

The exoplanets are presumed to be tidally locked. The six closest to TRAPPIST-1 have been determined to be rocky, while the seventh, TRAPPIST-1h, requires additional observations to determine its characteristics due to its longer orbital period.

Mass estimates for the planets range from 0.41 Earth masses (M_⊕) to 1.38 M_⊕. Radii range from 0.76 Earth radii (R_⊕) to 1.13 R_⊕.

Spitzer, Hubble, and other telescopes will continue to make observations of the TRAPPIST-1 planetary system, but the best data will likely come from the James Webb Space Telescope (JWST), which is scheduled to launch in late 2018. JWST will allow the atmospheres and temperatures of many exoplanets to be characterized, which will help to settle whether the "habitable zones" of red dwarf stars are actually hospitable.

Artist illustrations and data for the TRAPPIST-1 system compared to Mercury, Venus, Mars, and Earth.

Here's a website dedicated to the star.

Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1 (DOI: 10.1038/nature21360) (DX)

Original Submission

takyon writes:

A "biomarker" molecule presumed to indicate the presence of industrial or biological activity has been found to be naturally occurring in interstellar clouds:

A molecule once thought to be a useful marker for life as we know it has been discovered around a young star and at a comet for the first time, suggesting these ingredients are inherited during the planet-forming phase.

The discovery of methyl chloride was made by the ground-based Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and by ESA's Rosetta spacecraft following Comet 67P/Churyumov–Gerasimenko. It is the simplest member of a class of molecules known as organohalogens, which contain halogens, such as chlorine or fluorine, bonded with carbon.

Methyl chloride is well known on Earth as being used in industry. It is also produced naturally by biological and geological activity: it is the most abundant organohalogen in Earth's atmosphere, with up to three megatonnes produced a year, primarily from biological processes.

As such, it had been identified as a possible 'biomarker' in the search for life at exoplanets. This has been called into question, however, now it is seen in environments not derived from living organisms, and instead as a raw ingredient from which planets could eventually form.

This is also the first time an organohalogen has been detected in space, indicating that halogen- and carbon-centred chemistries are more intertwined than previously thought.

Also at the Harvard-Smithsonian Center for Astrophysics.

Protostellar and cometary detections of organohalogens (open, DOI: 10.1038/s41550-017-0237-7) (DX)

Original Submission

takyon writes:

Mars colonists could create a carbon dioxide plasma in order to supply oxygen to their settlement(s):

The atmosphere on Mars is 96 per cent carbon dioxide, says Vasco Guerra at the University of Lisbon in Portugal. This can be split to extract breathable oxygen and carbon monoxide, a fuel that could give us a "gas station on the Red Planet", he says. He and his team calculate that creating a carbon dioxide plasma — a mush of ions made by passing an electric current through a gas — could split carbon dioxide from oxygen more easily on Mars than on Earth.

The lower atmospheric pressure on Mars would allow us to create plasmas without the vacuum pumps or compressors necessary on Earth. Also, the temperature of around -60°C is just right to let the plasma more easily break one of the chemical bonds that keeps carbon and oxygen tightly bound, while preventing the carbon dioxide from re-forming.

For now, this is largely theoretical, but they say such a system needing only 150 to 200 Watts for 4 hours each 25-hour Mars day could produce 8 to 16 kilograms of oxygen. "The International Space Station currently consumes oxygen in the range of 2 to 5 kilograms per day, so this would be enough to support a small settlement," says Guerra.

The case for in situ resource utilisation for oxygen production on Mars by nonequilibrium plasmas (open, DOI: 10.1088/1361-6595) (DX)

Original Submission

takyon writes:

According to a new fossil analysis, previously described Australian fossils do contain evidence of 3.5-billion-year-old microbial life. However, the complexity of the fossilized microbes suggests that life arose much earlier, possibly as far back as 4 billion years ago:

In 1992, researchers discovered evidence of what was then potentially the earliest life on Earth: 3.5-billion-year-old microscopic squiggles encased in Australian rocks. Since then, however, scientists have debated whether these imprints truly represent ancient microorganisms, and even if they do, whether they're really that old. Now, a comprehensive analysis of these microfossils suggests that these formations do indeed represent ancient microbes, ones potentially so complex that life on our planet must have originated some 500 million years earlier.

The new work indicates these early microorganisms were surprisingly sophisticated, capable of photosynthesis and of using other chemical processes to get energy, says Birger Rasmussen, a geobiologist at Curtin University in Perth, Australia, who was not involved with the work. The study "will probably touch off a flurry of new research into these rocks as other researchers look for data that either support or disprove this new assertion," adds Alison Olcott Marshall, a geobiologist at the University of Kansas in Lawrence who was not involved in the effort.

[...] The analysis detected several distinct carbon ratios in the material [DOI: 10.1073/pnas.1718063115] [DX], Schopf, Valley, and colleagues report today in the Proceedings of the National Academy of Sciences. Two types of microfossils had the same carbon ratio as modern bacteria that use light to make carbon compounds that fuel their activities—a primitive photosynthesis that did not involve oxygen. Two other types of microfossils had the same carbon ratios as microbes known as archaea that depend on methane as their energy source—and that played a pivotal role in the development of multicellular life. The ratio of a final type of microfossil indicated that this organism produced methane as part of its metabolism.

That there are so many different carbon ratios strengthens the case that these are real fossils, Schopf says. Any inorganic processes that could have created the squiggles would be expected to leave a uniform carbon ratio signature, he says. The fact that microbes were already so diverse at this point in Earth's history also suggests that life on our planet may date back to 4 billion years ago, he says. Other researchers have found signs of life dating back at least that far, but those findings are even more controversial than Schopf's.

Also at University of Wisconsin-Madison.

Previously: Ancient Rocks Record First Evidence for Photosynthesis That Made Oxygen
3.7 Billion-Year-Old Fossil Found
Oldest Evidence of Life on Earth Found in 3.77-4.28 Billion Year Old Fossils
Earliest Known Evidence for Microbial Life on Land: 3.48 Billion Years Old

Original Submission

An Anonymous Coward writes:

A new study suggests a biosignature that the James Webb Space Telescope could search for:

The new study looks at the history of life on Earth, the one inhabited planet we know, to find times where the planet's atmosphere contained a mixture of gases that are out of equilibrium and could exist only in the presence of living organisms — anything from pond scum to giant redwoods. In fact, life's ability to make large amounts of oxygen has only occurred in the past one-eighth of Earth's history.

By taking a longer view, the researchers identified a new combination of gases that would provide evidence of life: methane plus carbon dioxide, minus carbon monoxide.

"We need to look for fairly abundant methane and carbon dioxide on a world that has liquid water at its surface, and find an absence of carbon monoxide," said co-author David Catling, a UW professor of Earth and space sciences. "Our study shows that this combination would be a compelling sign of life. What's exciting is that our suggestion is doable, and may lead to the historic discovery of an extraterrestrial biosphere in the not-too-distant future."

Also at Popular Mechanics.

Disequilibrium biosignatures over Earth history and implications for detecting exoplanet life (open, DOI: 10.1126/sciadv.aao5747) (DX)

Original Submission