Meteorites that crashed onto Earth billions of years ago may have provided the phosphorous essential to the biological systems of terrestrial life.
The meteorites are believed to have contained a phosphorus-bearing mineral called schreibersite, and scientists have recently developed a synthetic version that reacts chemically with organic molecules, showing its potential as a nutrient for life.
Phosphorus is one of life’s most vital components, but it often goes unheralded. It helps form the backbone of the long chains of nucleotides that create RNA and DNA; it is part of the phospholipids in cell membranes; and is a building block of the coenzyme used as an energy carrier in cells, adenosine triphosphate (ATP).
Yet the majority of phosphorus on Earth is found in the form of inert phosphates that are insoluble in water and are generally unable to react with organic molecules. This appears at odds with phosphorus’ ubiquity in biochemistry, so how did phosphorus end up being critical to life?
In 2004, Matthew Pasek, an astrobiologist and geochemist from the University of South Florida, developed the idea that schreibersite [(Fe, Ni)3P], which is found in a range of meteorites from chondrites to stony-iron pallasites, could be the original source of life’s phosphorus. Because the phosphorus within schreibersite is a phosphide, which is a compound containing a phosphorus ion bonded to a metal, it behaves in a more reactive fashion than the phosphate typically found on Earth.
Finding naturally formed schreibersite to use in laboratory experiments can be time-consuming when harvesting from newly fallen meteorites and expensive when buying from private collectors. Instead, it has become easier to produce schreibersite synthetically for use in the laboratory.
Natural schreibersite is an alloy of iron, phosphorous and nickel, but the common form of synthetic schreibersite that has typically been used in experiments is made of just iron and phosphorus, and is easily obtainable as a natural byproduct of iron manufacturing. Previous experiments have indicated it reacts with organics to form chemical bonds with oxygen, the first step toward integrating phosphorous into biological systems.
However, since natural schreibersite also incorporates nickel, some scientific criticism has pointed out that the nickel could potentially alter the chemistry of the mineral, rendering it non-reactive despite the presence of phosphides. If this were the case, it would mean that the experiments with the iron-phosphorous synthetic schreibersite would not represent the behavior of the mineral in nature.
“There was always this criticism that if we did include nickel it might not react as much,” said Pasek.
Pasek and his colleagues have addressed this criticism by developing a synthetic form of schreibersite that includes nickel.
In a recent paper published in the journal Physical Chemistry Chemical Physics, Pasek and lead author and geochemist Nikita La Cruz of the University of Michigan show how a form of synthetic schreibersite that includes nickel reacts when exposed to water. As the water evaporates, it creates phosphorus-oxygen (P-O) bonds on the surface of the schreibersite, making the phosphorus available to life. The findings seem to remove any doubts as to whether meteoritic schreibersite could stimulate organic reactions.
“Biological systems have a phosphorus atom surrounded by four oxygen atoms, so the first step is to put one oxygen atom and one phosphorous atom together in a single P-O bond,” Pasek explained.
Terry Kee, a geochemist at the University of Leeds and president of the Astrobiology Society of Britain, has conducted his own extensive work with schreibersite and, along with Pasek, is one of the original champions of the idea that it could be the source of life’s phosphorus.
“The bottom line of what [La Cruz and Pasek] have done is that it appears that this form of nickel-flavored synthetic schreibersite reacts pretty much the same as the previous synthetic form of schreibersite,” Kee said.
Pasek described how meteors would have fallen into shallow pools of water on ancient Earth. The pools would then have undergone cycles of evaporation and rehydration, a crucial process for chemical reactions to take place. As the surface of the schreibersite dries, it allows molecules to join into longer chains. Then, when the water returns, these chains become mobile, bumping into other chains. When the pool dries out again, the chains bond and build ever larger structures.
“The reactions need to lose water in some way in order to build the molecules that make up life,” said Pasek. “If you have a long enough system with enough complex organics, then, hypothetically, you could build longer and longer polymers to make bigger pieces of RNA. The idea is that at some point you might have enough RNA to begin to catalyze other reactions, starting a chain reaction that builds up to some sort of primitive biochemistry, but there’s still a lot of steps we don’t understand.”
Demonstrating that nickel-flavored schreibersite, of the sort contained in meteorites, can produce phosphorus-based chemistry is exciting. However, Kee said further evidence is needed to show that the raw materials of life on Earth came from space.
“I wouldn’t necessarily say that the meteoric origin of phosphorus is the strongest idea,” he said. “Although it’s certainly one of the more pre-biotically plausible routes.” [Fallen Stars: A Gallery of Famous Meteorites]
Despite having co-developed much of the theory behind schreibersite with Pasek, Kee pointed out that hydrothermal vents could rival the meteoritic model. Deep-sea volcanic vents are already known to produce iron-nickel alloys such as awaruite, and Kee says that the search is now on for the existence of awaruite’s phosphide equivalent in the vents: schreibersite.
“If it could be shown that schreibersite can be produced in the conditions found in vents — and I think those conditions are highly conducive to forming schreibersite — then you’ve got the potential for a lot of interesting phosphorylation chemistry to take place,” said Kee
Pasek agreed that hydrothermal vents could prove a good environment to promote phosphorus chemistry, with the heat driving off the water to allow the P-O bonds to form. “Essentially it’s this driving off of water that you’ve got to look for,” he added.
Pasek and Kee both agreed that it is possible that both mechanisms — the meteorites in the shallow pools and the deep-sea hydrothermal vents — could have been at work during the same time period and provided phosphorus for life on the young Earth. Meanwhile David Deamer, a biologist from the University of California, Santa Cruz, has gone one step further by merging the two models, describing schreibersite reacting in hydrothermal fields of bubbling shallow pools in volcanic locations similar to those found today in locations such as Iceland or Yellowstone National Park.
Certainly, La Cruz and Pasek’s results indicate that schreibersite becomes more reactive as the environment in which it exists gets warmer.
“Although we see the reaction occurring at room temperature, if you increase the temperature to 60 or 80 degrees Celsius [140 or 176 degrees Fahrenheit], you get increased reactivity,” said Pasek. “So, hypothetically, if you have a warmer Earth, you should get more reactivity.”
One twist to the tale is the possibility that phosphorus could have bonded with oxygen in space, beginning the construction of life’s molecules before ever reaching Earth. Schreibersite-rich grains coated in ice and then heated by shocks in planet-forming disks of gas and dust could potentially have provided conditions suitable for simple biochemistry. While Pasek agreed with that idea in principle, he said he has “a hard time seeing bigger things like RNA or DNA forming in space without fluid to promote them.”
The most detailed 3D map yet of a billion stars in the Milky Way galaxy was released today (Sept. 14), along with a sneak peek at brand-new data on millions of stars collected by the European Space Agency’s Gaia spacecraft.
Gaia has been scanning the sky to create a catalog of more than a billion stars in and around the Milky Way since 2014. Today’s first data release includes precise positions and brightness of 1.142 billion stars, plus distances and motions of more than 2 million stars. ESA scientists used the observations to create this stunning fly-through of a packed star cluster.
Just 14 months into its 5-year mission, Gaia’s data release is only the beginning of loads of new information about our galaxy that Gaia is expected to produce. The mission will ultimately build the most comprehensive, detailed and accurate star catalog of all time.
“Gaia is at the forefront of astrometry, charting the sky at precisions that have never been achieved before,” ESA’s Science Director Alvaro Giménez said in a statement.
Data from Gaia will be used not just for constructing a gigantic and unprecedented 3D map of the Milky Way, but it will also inspire new research. For example, knowing the stars’ positions, movements and other physical qualities could help researchers study the structure and history of the Milky Way galaxy.
While this may be the biggest and most ambitious galaxy-mapping endeavor yet, the vast amount of stars observed in this mission will represent only about 1 percent of all of the stars in the Milky Way galaxy.
A massive ice giant may be traveling through the outer solar system. Dubbed “Planet Nine,” the hypothetical world was proposed to exist after scientists noticed that a handful of objects beyond Pluto had been shaken up in unusual orbits. Search parties have formed to find the unseen planet, with optimistic hopes of spotting it within a year.
“It’s not crazy; this is the kind of stuff people are finding all the time,” co-discoverer Mike Brown, at the California Institute of Technology, told Space.com earlier this year. Brown and lead author Konstantin Batygin, also at CalTech, published a paper in January 2016 suggesting that a massive planet could be stirring up the icy bodies of the Kuiper Belt, a ring of material at the edge of the solar system.
“We just need to go out and cover a good swath of the sky.”
An unseen planet
Pluto makes its home at the edge of the Kuiper Belt, a region of ice-covered rocks left over from the formation of the solar system. Batygin and Brown noticed that several of the objects had similarities in their orbits, which suggested they were affected by a massive body. The usual suspects would be the solar system’s giant planets, but the objects the pair spotted were too far away to be affected by the behemoths.
By analyzing the strange orbits of the objects, Batygin and Brown proposed the presence of a new planet in the solar system, an object four times as large as Earth and 10 times as massive. They traced the possible orbit of the unseen giant, which they called “Planet Nine.” To create the observed disturbances, they mapped an orbit that comes as close as 200 astronomical units (AU) from the sun and travel as far away as 1,200 AU. (One AU is the distance from Earth to the sun — about 93 million miles, or 150 million kilometers.)
Not everyone is convinced that an enormous giant is skulking around the edges of the solar system. Ann-Marie Madigan, a postdoctoral researcher at the University of California Berkeley, found that the objects could “self-organize,” pushing and pulling one another into their unusual orbits. Working with co-author Michael McCourt of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, the pair found that if the objects in the scattered disk roughly equal the mass of Earth, they could have dragged themselves to their current orbits within about 600 million years of the solar system’s birth, omitting the need for Planet Nine’s interference.
According to Batygin and Brown, however, the Planet Nine scenario is more probable, because current surveys suggest there isn’t enough mass in the region. In their research, they note that the disk of material that birthed the planets may have started out with enough mass, but interactions with the giant planets would have quickly tossed it out of the solar system.
Another study suggested that Planet Nine could be tugging on NASA’s Cassini probe, orbiting Saturn. Agnès Fienga at the Côte d’Azur Observatory in France and her colleagues added Planet Nine to a theoretical model to see if the proposed world could solve the mystery of tiny changes in the spacecraft’s orbit that existing solar system objects cannot account for. If the missing planet lies about 600 AUs away toward the constellation Cetus, the puzzling perturbations can be accounted for.
According to Cassini’s mission managers, however, the spacecraft isn’t actually experiencing any mysterious anomalies.
“Although we’d love it if Cassini could help detect a new planet in the solar system, we do not see any perturbations in our orbit that we cannot explain with our current models,” said Earl Maize, Cassini project manager at JPL, in a statement.
Other objects in the Kuiper Belt may help nail down the case for the world. Research by Renu Halhotra, Kathryn Volk and Xianyu Wang, all at the University of Arizona, reveal half a dozen ice-cover rocks whose orbits appear to fit with the presence of a distant planet.
“It’s a different line of evidence than Mike Brown and Konstantin Batygin proposed,” Volk told Space.com.
Where did it come from?
A planet in the outer solar system today has to come from somewhere. Without directly seeing it, scientists can only model possibilities for the massive world.
One possibility is that the sun somehow managed to gravitationally grab onto a free-floating world or a planet orbiting another star and add it to the solar system’s crown. Computer simulations performed by Gongjie Li and Fred Adams, both of the CfA, suggest that the odds of this happening are less than 2 percent.
If Planet Nine didn’t come from outside the solar system, then it must have come from within. Models performed by Scott Kenyon of the CfA and Benjamin Bromely of the University of Utah suggest there’s a good chance the hypothetical world could have been born where it was, or been booted into the outer solar system by interactions with the giant planets.
“The nice thing about these scenarios is that they’re observationally testable,” Kenyon said in a statement.
“A scattered gas giant will look like a cold Neptune, while a planet that formed in place will resemble a giant Pluto with no gas.”
Not everyone is waiting to see the planet before trying to dive inside of it. Astrophysics professor Christoph Mordasini and his doctoral student Esther Linder, both of the University of Bern in Switzerland, modeled what astronomers might see when they spot Planet Nine.
Assuming that it is a smaller version of the ice giants Uranus and Neptune, with hydrogen and helium dominating its atmosphere, the pair calculated that a 10-Earth-mass Planet Nine would be about 3.7 times wider than our planet. Temperatures would average minus 375 degrees Fahrenheit (minus 226 degrees Celsius).
“This means that the planet’s emission is dominated by the cooling of its core,” Linder said in a statement.
Sunlight would contribute very little to the light of the planet, making it brighter in the infrared wavelengths than in visible light.
Although the world remains unseen, that doesn’t mean we should fear it. Reports by the New York Post published in April claimed that Planet Nine could hurl asteroids and comets toward Earth, with potentially devastating consequences. The video, which had several factual errors, was dismissed by Brown.
“Hey, so … fun fact? Planet Nine is not going to cause the Earth’s destruction. If you read that it will, you have discovered idiotic writing!” Brown said via his Twitter account, @plutokiller.
He also dismissed the idea that the world played a role in mass extinctions of the past. While the planet orbits a significant distance from the sun, it isn’t quite far enough out to stir up the Oort Cloud, the region of icy comets beyond the Kuiper Belt. With a 10,000-year orbit, it would also constantly bombard the Earth, Brown said.
“I suspect it has something like zero effect on us, he told Space.com previously.
Hunting the unseen
Planet Nine remains hypothetical; no one has actually seen the world. But that doesn’t mean scientists aren’t searching for it. Batygin and Brown started off by searching through previous skymaps, hunting their unseen world.
“We dumpster-dived into the existing observational data to search for Planet Nine,” Batygin said.” Because we didn’t find it we were able to rule out parts of its orbit.”
Exoplanet researcher Nicolas Cowan of McGill University in Montreal thinks Planet Nine might show up in present and future surveys of the cosmic microwave background. Depending on the planet’s orbit, it could also be picked up by the Dark Energy Survey, a project in the Southern Hemisphere designed to probe the acceleration of the universe. NASA’s WISE instrument should also be able to spot the giant, helping to narrow down the potential paths of the planet.
Linder and Mordasini remain cautious. According to their models, existing surveys would likely be incapable of spotting the world if it weighs in at less than 20 Earth masses, especially if it was far enough away.
Batygin and Brown are trying to obtain telescope time on the Subaru Telescope on Mauna Kea in Hawaii. They’re asking for roughly 20 nights of observing, a significant amount of time on a powerful instrument that is constantly in use.
“It’s a pretty big request compared to what other people generally get on the telescope,” Brown told Space.com.
“We’ll see if they bite.”
If they do, he estimated that the planet could be spotted within a year.
Astronomers have discovered another dwarf planet in the Kuiper Belt, the ring of icy objects beyond Neptune. But this newfound world, dubbed 2015 RR245, is much more distant than Pluto, orbiting the sun once every 700 Earth years, scientists said. (Pluto completes one lap around the sun every 248 Earth years.) You can see an animation of the new dwarf planet’s orbit here.
“The icy worlds beyond Neptune trace how the giant planets formed and then moved out from the sun,” discovery team member Michele Bannister, of the University of Victoria in British Columbia, said in a statement. “They let us piece together the history of our solar system.” [Meet the Solar System’s Dwarf Planets]
“But almost all of these icy worlds are painfully small and faint; it’s really exciting to find one that’s large and bright enough that we can study it in detail,” Bannister added.
The exact size of 2015 RR245 is not yet known, but the researchers think it’s about 435 miles (700 kilometers) wide. Pluto is the largest resident of the Kuiper Belt, with a diameter of 1,474 miles (2,371 km).
The research team first spotted 2015 RR245 in February of this year, while poring over images that the Canada-France-Hawaii Telescope in Hawaii took in September 2015 as part of the ongoing Outer Solar System Origins Survey (OSSOS).
“There it was on the screen — this dot of light moving so slowly that it had to be at least twice as far as Neptune from the sun,” Bannister said.
OSSOS has discovered more than 500 objects beyond Neptune’s orbit, but 2015 RR245 is the first dwarf planet that the survey has found, the scientists said.
Dwarf planets are massive enough to be crushed into spheres by their own gravity, but they have not “cleared their neighborhood” of other objects, which differentiates them from “normal” planets such as Earth and Saturn. This definition, which was devised by the International Astronomical Union in 2006, led to Pluto’s controversial reclassification as a dwarf planet.
Astronomers are still working out the details of 2015 RR245’s highly elliptical orbit, but the object appears to come as close to the sun as 34 astronomical units (AU), and farther away than 120 AU. (One AU is the average Earth-sun distance — about 93 million miles, or 150 million km.)
2015 RR245 — which will get a catchier, official name at some point — will make its closest approach to the sun in 2096, the researchers said.
Other confirmed dwarf planets in the Kuiper Belt region include Pluto, Eris, Haumea and Makemake. Several other objects in this distant realm, including Sedna, Quaoar and 2007 OR10, probably meet the dwarf-planet criteria as well, scientists have said.
Saturn’s biggest moon, Titan, may possess the kind of chemistry that could eventually lead to life, albeit without water, a new study finds.
Titan is larger than the planet Mercury, making it the biggest of the more than 60 known moons orbiting Saturn. The moon’s surface is covered in rivers, lakes and oceans of methane, which also rains from the sky. This methane cycle, similar to Earth’s water cycle, can make Titan seem like an equally familiar and alien location.
Now, using computer models, a group of researchers has shown that a chemical on Titan’s surface could lay the groundwork for the formation of life. In Titan’s cold atmosphere, this ingredient can act as a catalyst for chemical reactions, and potentially absorb energy from sunlight, even through Titan’s thick clouds. [Photos of Saturn’s moon Titan]
Although Earth and Titan have major differences — for instance, Titan is much colder, is poor in oxygen and lacks surface water — Titan has a surface atmospheric pressure similar to Earth’s, and is the only place in the solar system except Earth where rainfall erodes the landscape.
On Earth, water flows in a cycle, raining from the sky, pouring down rivers and streams to oceans and lakes, and evaporating under sunlight into mist, forming clouds that eventually rain down. Probes sent to Titan have revealed that methane flows in a similar cycle of rivers, lakes and clouds over an ice crust.
The methane cycle, frigid climate and lack of liquid water on Titan’s surface make it a window into what life might be like on a world radically different from — and yet, in some ways, very similar to — Earth. In the new research paper, Jonathan Lunine, a planetary scientist at Cornell University in Ithaca, New York, and his colleagues investigated what prebiotic chemistry — the kinds of reactions that might lead to life — might be like on Titan-like worlds.
The scientists focused on a chemical known as hydrogen cyanide, which previous research has suggested might be central to the origin of life on Earth, the researchers said. (A cyanide is any molecule that contains a group made of a carbon atom and a nitrogen atom bonded together. Hydrogen cyanide is made of hydrogen, carbon and nitrogen, all linked together in a row. Cyanides are generally extremely toxic.)
Hydrogen cyanide can serve as a precursor to amino acids and nucleic acids, which are the building blocks of key molecules of Earth life, such as proteins and DNA. Prior work found that hydrogen cyanide is the most abundant hydrogen-containing molecule in Titan’s atmosphere.
Previous experiments suggested that hydrogen cyanide molecules often link together to form a compound known as polyimine. Now, the research team’s computer models show that polyimine has interesting properties that might support prebiotic chemistry in the kind of ultracold temperatures seen on Titan.
The scientists found that polyimine can absorb a wide spectrum of light, including wavelengths that can penetrate Titan’s smoggy atmosphere. This suggests that it can soak up energy from the sun that polyimine could then use in chemical reactions on Titan’s surface, they said.
Moreover, polyimine has a flexible backbone, meaning that it can adopt several different structures, from sheets to more coiled shapes. The researchers suggested that some of these structures might act like catalysts to accelerate prebiotic chemical reactions. In addition, other shapes could interact to form more complex structures that could host prebiotic chemistry — for instance, porous stacks of sheets could form. These stacks of sheets, in turn, could support delicate chemical reactions in them and let molecules drift in and out, the researchers said.
“We are not saying we created Titan life in a computer, or even structures that might be in life on Titan,” Lunine told Space.com. “We are saying that the early steps toward structures, catalysis and absorption of energy might be possible on Titan with polymers like those we modeled.”
The researchers noted that polyimine might be present on Titan and might have escaped detection because Titan’s murky atmosphere would make it difficult to identify. They added that future missions to Titan could be designed to look for polyimine and learn more about a potentially exotic kind of biochemistry.
“We need to go back to Titan and analyze the surface composition and search for polymers,” Lunine said.
The scientists detailed their findings online July 4 in the journal Proceedings of the National Academy of Sciences.
If Pluto’s subsurface ocean had frozen over completely, it would have formed highly pressurized ice that would have caused the dwarf planet to shrink, according to new research. The canyons and valleys on Pluto seem to have formed as the dwarf planet swelled up, rather than as it shrank, indicating that a liquid ocean most likely sits beneath the thick ice crust today, researchers said in the study.
“Thanks to the incredible data returned by [NASA’s New Horizons mission], we were able to observe tectonic features on Pluto’s surface [and] update our thermal evolution model with new data,” Noah Hammond, a graduate student at Brown University, said in a statement from the school. Hammond worked with his advisers — Amy Barr, of the Planetary Science Institute, and Marc Parmentier, also at Brown — to study the likelihood that a liquid ocean hides beneath Pluto’s .
When the New Horizons probe flew past Pluto last July, its images of the dwarf planet’s surface revealed deep faults, or fractures in the surface, hundreds of kilometers long, according to the statement from Brown. The long canyons appeared to form as Pluto’s crust expanded, Hammond said. “A subsurface ocean that was slowly freezing over would cause this kind of expansion,” he said.
It didn’t take long for scientists to conclude that Pluto once housed an ocean, but the question of whether it had already frozen over remained. Using updated measurements of Pluto’s diameter and density, Hammond’s model revealed that a frozen ocean beneath the crust would have changed from conventional water ice to a more compact, crystallized structure known as “ice II.” As the ice changed, the frozen ocean would have shrunk, creating an entirely different type of feature known as compressional fractures, which are not seen on Pluto’s surface.
“We don’t see the things on the surface we’d expect if there had been a global contraction,” Hammond said. “So we conclude that ice II has not formed, and therefore that the ocean hasn’t completely frozen.”
Ice II would have formed only if the dwarf planet’s outer shell were at least 160 miles (260 kilometers) thick, putting sufficient pressure on the underlying ice, the statement said. Under the thinner shell, the ocean could have remained regular ice, not shrinking at all.
Hammond’s model suggests that the shell might be closer to 190 miles (300 km) thick, thanks to high temperatures in the core, according to the paper. The addition of nitrogen and methane ice spotted on the surface of the tiny world may also help keep the water warm.
“Those exotic ices are actually good insulators,” Hammond said.
That means oceans could lie not only inside tiny Pluto but also in other similar worlds in the far reaches of the Kuiper Belt, the sphere of ice and rock at the edge of the solar system.
“That’s amazing to me,” Hammond said. “The possibility that you could have vast liquid water ocean habitats so far from the sun on Pluto — and that the same could also be possible on other Kuiper Belt objects as well — is absolutely incredible.”
The research was published online on June 15 in the journal Geophysical Research Letters.
Researchers studied the properties of nearly 9,000 near-Earth objects (NEOs) — asteroids and other bodies that come within 1.3 Earth-sun distances of our planet — to build a model of the overall NEO population.
This model seemed to have a problem, however: It predicted that astronomers should be seeing 10 times more NEOs that closely approach the sun — come within 9 million miles (15 million kilometers) or so of the star — than they actually observe.
The research team spent a year puzzling over this outcome before coming to a surprising conclusion: The missing NEOs are actually being destroyed as they get close to the sun, but long before they actually dive into the star.
“The discovery that asteroids must be breaking up when they approach too close to the sun was surprising, and that’s why we spent so much time verifying our calculations,” study co-author Robert Jedicke, of the University of Hawaii Institute for Astronomy, said in a statement.
The team’s work should help scientists better understand the NEO population in a variety of ways. For example, many meteors that light up Earth’s night skies are pieces of debris shed by parent NEOs on their laps around the sun. Such debris clouds travel on the same orbits as their parent bodies, but astronomers generally have trouble finding these NEOs. The new study suggests that this is because the parent objects have already been destroyed, the researchers said.
In addition, study team members determined that darker NEOs die farther from the sun than brighter ones do, which helps explain something astronomers already knew: Asteroids that approach the sun closely tend to be quite bright.
This finding implies that dark and bright asteroids may differ significantly in structure and composition, the researchers said.
“Perhaps the most intriguing outcome of this study is that it is now possible to test models of asteroid interiors simply by keeping track of their orbits and sizes,” lead author Mikael Granvik, of the University of Helsinki in Finland, said in the same statement. “This is truly remarkable and was completely unexpected when we first started constructing the new NEO model.”
Granvik and his colleagues built their model by studying nearly 100,000 images of NEOs acquired by the Catalina Sky Survey in Arizona over an eight-year period.
To date, scientists have identified and tracked almost 14,000 NEOs, but the overall population is thought to number in the millions. Astronomers think that most of these bodies begin their lives in the main asteroid belt between Mars and Jupiter, and then veer inward after experiencing gravitational nudges by Jupiter and/or Saturn. The new study was published online today (Feb. 17) in the journal Nature.
Invisible “plasma lenses” shaped like noodles, lasagna sheets or hazelnuts might lurk between stars in the Milky Way, researchers say.
This finding could help solve the longstanding mystery of where a major part of the galaxy’s matter is hiding, the scientists added.
Astronomers first detected clues of these mysterious structures 30 years ago as they monitored quasarsquasars, the brightest objects in the universe. Quasars are the most energetic form of active galactic nuclei, which are supermassive black holes in the centers of distant galaxies that release extraordinarily large amounts of light as they rip apart stars and gobble matter
Previous research found that radio waves from quasars could vary wildly in strength, a phenomenon technically known as an extreme scattering event. Astronomers suggested these events were due to clouds of plasma — that is, electrically charged particles. These clouds are essentially lumps in the thin gas that fills the space between the stars in the Milky Way.
“Lumps in this gas work like lenses, focusing and defocusing the radio waves, making them appear to strengthen and weaken over a period of days, weeks or months,” study lead author Keith Bannister, an astronomer at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia, said in a statement.
Previous research suggested these “plasma lenses” are huge — about 620 million miles (1 billion kilometers) wide, a distance nearly seven times the distance between Earth and the sun. Ones detected so far lie about 3,200 light-years away, nearly 800 times farther than the nearest star to Earth, Proxima Centauri.
Plasma lenses among the stars
Plasma lenses have been difficult to find, so much about them is a mystery. For instance, estimates suggested the pressures within these plasma lenses are about 1,000 times greater than the surrounding interstellar gas. It was uncertain how these structures could form and survive long enough for astronomers to detect as often as they have.
In addition, until now, scientists knew nothing about the shape of these plasma lenses. This made it difficult to figure out what these structures were or what their origins were.
Now astronomers have for the first time successfully detected a lensing event while it was happening. This helped them conduct follow-up analyses that permitted the first estimates of plasma lens shapes.
Researchers used the Australia Telescope Compact Array to scan about 1,000 active galactic nuclei for sudden changes in their radio waves. They detected a lensing event in 2014 that went on for a year in connection with the quasar PKS 1939-315, located in the constellation Sagittarius. Whereas old analyses of lensing events only monitored two radio frequencies, “our new method gave us 9,000 frequencies at once,” Bannister told Space.com. “It was like going from black-and-white TV to color.”
Based on their findings, the researchers suggest this plasma lens could neither be a spherical cloud nor a corrugated or bent sheet.
“We could be looking at a flat sheet, edge on,” study co-author Cormac Reynolds at CSIRO said in a statement. “Or we might be looking down the barrel of a hollow cylinder like a noodle, or at a spherical [hollow] shell like a hazelnut.”
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Detecting more of these plasma lenses could reveal their shapes, which could in turn shed light on their origins. Previous research suggested two potential origins for these plasma lenses. One involves plasma sheets, perhaps the remains of shock waves from supernovas, Bannister said. Another involves cold clouds pulled together by the force of their own gravity.
If the plasma lenses are shaped like sheets, they may be plasma sheets. If they are spherical hollow shells, then they may be cold clouds held together by their own gravity. If they are hollow tubes, they may be flux tubes, structures formed by magnetic fields in the interstellar medium, Bannister said.
If the plasma lenses are made up of cold clouds, that suggests that cold clouds must make up a substantial fraction of the Milky Way, Bannister said. If so, they could help solve the so-called “missing baryon problem.”
Normal matter is made up mostly of particles known as baryons, which include protons and neutrons found in the atoms making up planets, stars and galaxies. Normal matter only makes up about one-sixth of all matter in the universe, with the rest consisting of dark matter, a mysterious invisible substance detectable via its gravitational influence on normal matter.
However, even normal matter presents a puzzle, since theories of the formation and evolution of the universe predict there should be about two times more baryons than astronomers see. Cold clouds might help solve the missing baryon problem, but “proving that is still a long way off though,” Bannister said.
In the future, the Australian Square Kilometre Array Pathfinder (ASKAP) should find plasma lenses “in droves,” Bannister said. This may help solve the mystery of what these structures are, he noted.
The scientists detailed their findings in the Jan. 22 issue of the journal Science.
A previously unidentified highway of dust extends across the Milky Way, between the sun and the central bulge of the galaxy, scientists have found.
Called the “Great Dark Lane” by the astronomers who announced it, the dusty road twists in front of the bulge of the galaxy.
“For the first time, we could map this dust lane at large scales, because our new infrared maps cover the whole central region of the Milky Way,” Dante Minniti, a researcher at Universidad Andres Bello in Chile and lead author of a study describing the findings, told Space.com by email.
Mapping the Milky Way
The center of a spiral galaxy contains a collection of stars that bulge above and below the flatter spirals, much like an egg yolk. The arms that give the galaxies their classification twist around the bulge, often in a beautiful spiral (although sometimes they are more elongated). Lanes of dust often lie between these arms, which present a particular challenge to map out.
“It is very difficult to mapthe structure of our galaxy because we are inside, and it is very large and covered with dust clouds that are opaque in the optical,” Minniti said.
Working with a team of astronomers, Minniti used the European Space Observatory’s Vista Variables in the Via Lactea Survey (VVV), a project to scan the Milky Way using the VISTA telescope in Chile, to study the galaxy in the near-infrared. At this wavelength, telescopes are able to peer through the clouds of dust to a group of objects known as red clump (RC) stars lying within the bulge.
Red clump stars have helium-burning cores that generate a similar brightness no matter what their age or composition is. This makes them reliable distance indicators for astronomers.
Based on the measurement of 157 million stars, Minniti and his team found that the RC stars of the Milky Way’s bulgewere split into two colors — a difference they determined was caused by dust between the stars and the observers. The astronomers could see a sharp transition between the two distinct groups — the dusty Great Dark Lane dividing them.
The Great Dark Lane extends approximately 20 degrees across the sky, reaching both above and below the plane of the galaxy. It sits roughly 15,000 light-yearsfrom the solar system, although the team is still working to refine the distance. It lies outside of the bulge rather than being contained within it, they said.
If the dust passed through the bulge itself, the red clump stars of the center would have a patchier distribution, rather than a clean break, as some of the stars at a certain height above the plane would be in front of the dust and others would be behind it, the researchers said. Instead, all of the red clump stars contained within the bulge lie behind the dust, according to the study.
“Detailed maps and modeling are needed in order to test this important galactic feature,” the researchers wrote in their paper, which appeared in the journal Astronomy & Astrophysics last year.
When the monster back hole at the center of the Milky Way galaxy belched out an exceptionally high number of powerful X-ray flares last year, it made astronomers wonder — is this a sign that the beast chowed down on a passing gas cloud, or is this lack of cosmic etiquette typical for black holes?
The black hole at the center of the Milky Way, known as Sagittarius A* (Sgr A* for short), is typically very quiet – it doesn’t eat a lot of material, and there is relatively little light that radiates from the region around it. Which is why the apparent uptick in bright X-ray flares came as a surprise to scientists.
Could the bright flares seen in August 2014 have been caused by a gas cloud that passed too close to the black hole, and become an unsuspecting snack? And if that is the case, what does it tell scientists about what exactly happens to material that falls into a black hole? Alternatively, are these types of flare clusters typical of black holes, and an example of scientists’ limited understanding of these mighty beasts? Upcoming observations may shed some light on these dark objects. [Images: Milky Way’s Monster Black Hole Shreds … Something]
Bright flare activity increases
Packing a double punch of observational power, NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton space telescope have been observing Sgr A* (pronounced “Sagittarius A-star”) on and off since 1999. In the last three years, the total coverage time has increased thanks to a series of dedicated observation campaigns.
For long stretches, Chandra’s detectors would see only “quiescent” X-ray activity from Sgr A*, and then, suddenly, a bright flare would appear. The center of the Milky Way is one of the most densely populated regions of the galaxy, and the view between Earth and Sgr A* is blocked by stars and gas clouds. The Chandra scientists cherished the light that managed to make its way to their detectors, according to Daryl Haggard, an astrophysicist at McGill University in Montreal, who studies the black hole using Chandra data.
Haggard is a co-author on a new study suggesting there was a two- to threefold increase in the number of bright flares emitted by Sgr A* beginning in August 2014 and extending through November 2014 (the paper does not show an overall increase in the flare rate). In one particularly active period, five bright X-ray flares burst forth from Sgr A* in a time frame that would typically see only one. One of the flares, seen in September, was three times brighter than any other flare detected from that region. The new paper looked at 15 years of Chandra and XMM-Newton data, as well as data from the SWIFT space telescope, in an effort to show that the increase was not merely a result of greater observation time.
What was happening to cause the increase? According to the new research, there are two leading ideas.
G2, the mystery object
The first hypothesis involves a controversial object called G2. In 2011, a group of astronomers using the Very Large Telescope in Chile announced that this cosmic daredevil was going to make a very tight swing around Sgr A*. What would happen during this close approach was a subject of hot debate, because scientists couldn’t say for sure what G2 was – a pure dust cloud or a compact object surrounded by a dust cloud.
If G2 is a solid object, then it should have swung around Sgr A* without being pulled past the event horizon, beyond which nothing, not even light, can escape. But if it is pure gas, scientists predicted that the gravity of the black hole would smear it like a wisp of smoke, and a sizable amount of material would become lunch for Sgr A*. That would, theoretically, produce an increase in the light emitted from the region around the black hole, because when material falls into a black hole it accelerates rapidly, causing it to radiate light.
That means that if G2 is a dust cloud, it could have provided scientists with the first real-time, short-term observation of a black hole eating. To watch one of the most monstrous cosmic creatures in the universe devour a meal right in our own backyard would be an unrivaled opportunity for scientists. It would tell them about how black holes grow over their lifetimes, and provide new insights into the strange physics that takes place near the edge of these extreme gravity wells. Imagine a scientist who is trying to study lions in the wild, but never getting to see them hunt and devour their prey — G2 might finally let scientists watch Sgr A* in action.
The excitement was a palpable lead-up to G2’s close approach to Sgr A*. Andrea Ghez, an astrophysicist at the University of California at Los Angeles and one of the scientists who confirmed the existence of Sgr A*, said it was one of the “most watched events in astronomy in my career.”
Chandra saw nothing, nor did any of the other telescopes observing at the time.
Stefan Gillessen, a researcher at the Max Planck Institute for Extraterrestrial Physics in Germany and one of the lead proponents of the gas cloud theory, argued that G2 might still be a pure gas cloud, but that the dynamics of how and when it would be pulled into Sgr A* were different than originally predicted. Scientists don’t fully understand how material might behave around a black hole.
The new suggestion that Sgr A* released an increased number of bright flares in late 2014 could be the missing light show, according to Gabriel Ponti, a research fellow with the Max Planck group and the lead author on the new paper. Perhaps the material from G2 took longer than expected to fall toward the black hole and radiate.
“A year or so ago, we thought [G2] had absolutely no effect on Sgr A*, but our new data raise the possibility that that might not be the case,” Ponti said in a statement from Chandra.
A cluster of flares
Ponti cautions that the new research cannot confirm the connection between the flare activity and G2 — there’s no evidence to show that it isn’t just a coincidence. Plus, the paper points out that observations in infrared light seem to show that G2 has survived its trip around Sgr A*, suggesting it is not a pure gas cloud.
This doesn’t rule out the possibility that some of the gas from G2 was pulled into the black hole, but it means scientists would have to have a new model for how much gas could be syphoned from G2. And that raises the question of how quickly material moves through the region around a black hole, and around Sgr A* in particular. Does it flow down to the black hole’s gaping maw in a smooth, quickly moving stream, like cream moving through coffee? Or is it slow, like molasses across asphalt? If this burst of flare activity is due to G2 passing by, it would suggest that material falls very quickly, according to Haggard. In fact, it would suggest that material is basically in free- fall as it gets closer to the black hole’s event horizon. [The Strangest Black Holes in Space]
The likelihood of a G2 connection to the increased flare activity “seems tenuous to me,” Haggard told Space.com. She prefers an alternative possibility — that black holes normally exhibit “flare clustering,” or bursts of activity that vary from the “average” behavior they exhibit most of the time.
Ponti writes in his blog post for the Chandra website that other black holes that accrete matter at a similar rate to Sgr A* (but which are millions of times less massive) also show “long-term modulation in their flaring properties.” (Another factor to consider is that an object called G1, spotted before G2 and with a similar physical appearance, approached Sgr A* at a similar distance in 2001, but there was “no particular evidence for anything unusual happening as a result of G1’s passage.” However, he also notes that “the X-ray monitoring was much sparser” at the time.)
Illuminating a black hole
Scientists are still trying to understand why black holes like Sgr A* might release flares in periodic clusters, rather than evenly over time. It could have to do with how the gravitational pull of the black hole destroys matter that falls toward it, perhaps breaking it up into clumps, like a string of pearls that then fall in one after the other, each creating their own flare. It could also have to do with the magnetic properties of the black hole.
The Event Horizon Telescope, a worldwide network of radio telescopes, is currently dedicated to studying the monstrous beast that lives at the heart of Earth’s galactic home. No data has come out of the project yet, but the collaboration may provide the best-ever images of a black hole.
“At present, we don’t know whether the observed variation has anything to do with G2 or not and we are eager to know what the new data collected in 2015 will tell us,” Ponti wrote in a blog post on Harvard University’s Chandra website.
The object known as G2 may not have provided a snack for Sgr A*, the way so many people hoped it would. But it is nonetheless a fascinating object, potentially something that astronomers have never seen before. Ghez’s group of researchers at UCLA have proposed that it may be two stars that merged into one, and they’re wondering if these types of merged stars are typical around Sgr A*, and why.
Sgr A* is the nearest example we have of one of the most captivating creatures in the universe: An object with a gravitational pull so powerful it can bend light, or stop it from ever escaping. There are black holes in the universe that are brighter than entire galaxies, and others that are almost completely invisible. Scientists still aren’t sure if falling into a black hole would involve being shredded into long strips like spaghetti, or crushed by all the material that ever fell in before. The flares detected by Chandra and XMM provide clues about what happens to those that enter the cosmic lion’s den.
The mystery of Mars’ missing atmosphere is one big step closer to being solved.
A previous hypothesis had suggested that a significant part of the carbon from Mars’ atmosphere, which is dominated by carbon dioxide, could have been trapped within rocks via chemical processes. However, new research suggests that there’s not enough carbon in deposits on the Red Planet’s surface to account for the huge amounts lost from the air over time.
“The biggest carbonate deposit on Mars has, at most, twice as much carbon in it as the current Mars atmosphere,” study co-author Bethany Ehlmann, of the California Institute of Technology (Caltech) and NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement
“Even if you combine all known carbon reservoirs together, it is still nowhere near enough to sequester the thick atmosphere that has been proposed for the time when there were rivers flowing on the Martian surface,” added Ehlmann, who worked with lead author Christopher Edwards, a former Caltech researcher currently with the U.S. Geological Survey.
Although Mars is dry today, scientists think the planet’s surface harbored large amounts of liquid water billions of years ago. Mars must have had a much thicker atmosphere back then, to keep the water from freezing or immediately evaporating, scientists say.
Carbon dioxide can be pulled from the atmosphere via chemical reactions with rocks, forming carbonate minerals. Previous research had suggested that the Red Planet might be covered with significant carbonate deposits, which could have locked up much of Mars’ lost atmosphere.
But Mars orbiters and rovers have found just a few concentrated carbonate deposits. The largest known carbonate-rich deposit on Mars is the Nili Fossae region, an area at least the size of Delaware and potentially as large as Arizona.
Edwards and Ehlmann used data captured by numerous Mars missions — including NASA’s Mars Global Surveyor orbiter, Mars Reconnaissance Orbiter, and Mars Odyssey orbiter — to estimate how much carbon is locked into Nili Fossae. Then, they compared that amount to what would be needed to form a dense, carbon-rich atmosphere that could sustain running water on the surface at the time that flowing rivers are thought to have carved extensive valley networks into the planet’s surface.
The Martian surface has been probed extensively by orbiters and landers, revealing only limited and scattered deposits of carbonate. Therefore, Edwards and Ehlmann deem it unlikely that so many large deposits have been overlooked by past examinations. Although very early deposits could be hidden beneath the Martian crust, their existence wouldn’t solve the mystery behind the atmosphere that existed when the river-carved valleys formed.
So, if the thick atmosphere didn’t become locked in carbonate deposits, what happened to it? One possibility is that it might have been lost to space from the top of the atmosphere — a phenomenon that NASA’s Curiosity rover has found evidence of in the past. Still, scientists aren’t certain how much of that loss occurred before the valleys formed. NASA’s MAVEN (Mars Atmosphere and Volatile Evolution) orbiter may help narrow down the mystery as it studies the Martian atmosphere.
“Maybe the atmosphere wasn’t so thick by the time of valley network formation,” Edwards said. “Instead of Mars that was wet and warm, maybe it was cold and wet with an atmosphere that had already thinned. How warm would it need to have been for the valleys to form? Not ver
“In most locations, you could have had snow and ice instead of rain,” Edwards said. “You just have to nudge above the freezing point to get water to thaw and flow occasionally, and that doesn’t require very much atmosphere.”
The research was published online Aug. 21 in the journal Geology.
The brightest nova of the century blasted lithium into space at 1.2 million mph (2 million km/h), new research reveals, cracking a long-standing mystery about the chemical balance of the universe.
Nova Centauri 2013 materialized in the sky in December 2013, caused by a huge nuclear explosion on a white dwarf star. This formed a new point in the constellation Centaurus, visible to the naked eye. Now, new measurements from the European Southern Observatory’s (ESO) La Silla facility in Chile reveal that the explosion is ejecting the element lithium, the first time that element has been seen in a nova system. This may help explain the topsy-turvy lithium distribution within stars, according to ESO officials.
“Understanding the amounts of lithium observed in stars around us today in the universe has given astronomers headaches,” ESO officials wrote in a statement. “Older stars have less lithium than expected, and some younger ones up to 10 times more.” The amount of lithium ejected from Nova Centauri is small, less than 1 billionth the mass of Earth’s sun. But the element’s presence in the nova supports a hypothesis in astronomy that a particular class of younger stars could have been built partially from lithium shot out of older stars. This would explain the younger bodies’ higher levels of lithium.
“It is a very important step forward,” study co-author Massimo Della Valle, from INAF–Osservatorio Astronomico di Capodimonte, Naples, and ICRANet, Pescara, Italy, said in the statement. “If we imagine the history of the chemical evolution of the Milky Way as a big jigsaw, then lithium from novae was one of the most important and puzzling missing pieces. In addition, any model of the Big Bang can be questioned until the lithium conundrum is understood.”Della Valle and another co-author, Luca Pasquini, an astronomer at University of Bologna in Italy, have been searching for traces of lithium in novas for over 25 years, according to the statement.
The lead scientist, Luca Izzo from Sapienza University of Rome and ICRANet, is excited too, although newer to the chase, he said in the statement: “It is very exciting to find something that was predicted before I was born and then first observed on my birthday in 2013!”
Planetary Resources deployed its first spacecraft from the International Space Station last month, and the Washington-based asteroid-mining company aims to launch a series of increasingly ambitious and capable probes over the next few years.
The goal is to begin transforming asteroid water into rocket fuel within a decade, and eventually to harvest valuable and useful platinum-group metals from space rocks.
“We have every expectation that delivering water from asteroids and creating an in-space refueling economy is something that we’ll see in the next 10 years — even in the first half of the 2020s,” said Chris Lewicki, Planetary Resources president and chief engineer Chris Lewicki.
“After that, I think it’s going to be how the market develops,” Lewicki told Space.com, referring to the timeline for going after asteroid metals.
“If there’s one thing that we’ve seen repeat throughout history, it’s, you tend to overpredict what’ll happen in the next year, but you tend to vastly underpredict what will happen in the next 10 years,” he added. “We’re moving very fast, and the world is changing very quickly around us, so I think those things will come to us sooner than we might think.”
Planetary Resources and another company, Deep Space Industries, aim to help humanity extend its footprint out into the solar system by tapping asteroid resources. (Both outfits also hope to make a tidy profit along the way, of course.)
This ambitious plan begins with water, which is plentiful in a type of space rock known as carbonaceous chondrites. Asteroid-derived water could do far more than simply slake astronauts’ thirst, mining advocates say; it could also help shield them from dangerous radiation and, when split into its constituent hydrogen and oxygen, allow voyaging spaceships to fill up their fuel tanks on the go.
The technology to detect and extract asteroid water is not particularly challenging or expensive to implement, Lewicki said. Scientific spacecraft routinely identify the substance on celestial bodies, and getting water out of an asteroid could simply involve bagging up the space rock and letting the sun heat it up.
Carbonaceous chondrites also commonly contain metals such as iron, nickel and cobalt, so targeting these asteroids could allow miners to start building things off Earth as well. That’s the logical next step beyond exploiting water, Lewicki said.
The “gold at the end of the rainbow,” he added, is the extraction and exploitation of platinum-group metals, which are rare here on Earth but are extremely important in the manufacture of electronics and other high-tech goods.
“Ultimately, what we want to do is create a space-based business that is an economic engine that really opens up space to the rest of the economy,” Lewicki said.
Developing off-Earth resources should have the effect of opening up the final frontier, he added.
“Every frontier that we’ve opened up on planet Earth has either been in the pursuit of resources, or we’ve been able to stay in that frontier because of the local resources that were available to us,” Lewicki said. “There’s no reason to think that space will be any different.”
Planetary Resources isn’t mining asteroids yet, but it does have some hardware in space. The company’s Arkyd-3R cubesat deployed into Earth orbit from the International Space Station last month, embarking on a 90-day mission to test avionics, software and other key technology.
Incidentally, the “R” in “Arkyd-3R” stands for “reflight.” The first version of the probe was destroyed when Orbital ATK’s Antares rocket exploded in October 2014; the 3R made it to the space station aboard SpaceX’s robotic Dragon cargo capsule in April. [Antares Rocket Explosion in Pictures]
Planetary Resources is now working on its next spacecraft, which is a 6U cubesat called Arkyd-6. (One “U,” or “unit,” is the basic cubesat building block — a cube measuring 4 inches, or 10 centimeters, on a side. The Arkyd-3R is a 3U cubesat.)
The Arkyd-6, which is scheduled to launch to orbit in December aboard SpaceX’s Falcon 9 rocket, features advanced avionics and electronics, as well as a “selfie cam” that was funded by a wildly successful Kickstarter project several years ago. The cubesat will also carry an instrument designed to detect water and water-bearing minerals, Lewicki said.
The next step is the Arkyd 100, which is twice as big as the Arkyd-6 and will hunt for potential mining targets from low-Earth orbit. Planetary Resources aims to launch the Arkyd-100 in late 2016, Lewicki said.
After the Arkyd 100 will come the Arkyd 200 and Arkyd 300 probes. These latter two spacecraft, also known as “interceptors” and “rendezvous prospectors,” respectively, will be capable of performing up-close inspections of promising near-Earth asteroids in deep space.
If all goes according to plan, the first Arkyd 200 will launch to Earth orbit for testing in 2017 or 2018, and an Arkyd 300 will launch toward a target asteroid — which has yet to be selected — by late 2018 or early 2019, Lewicki said.
“It is an ambitious schedule,” he said. But such rapid progress is feasible, he added, because each new entrant in the Arkyd series builds off technology that has already been demonstrated — and because Planetary Resources is building almost everything in-house.
“When something doesn’t work so well, we don’t have a vendor to blame — we have ourselves,” Lewicki said. “But we also don’t have to work across a contractural interface and NDAs [non-disclosure agreements] and those sorts of things, so that we can really find a problem with a design within a week or two and fix it and move forward.”
For its part, Deep Space Industries is also designing and building spacecraft and aims to launch its first resource-harvesting mission before 2020, company representatives have said.
Extracting and selling asteroid resources is in full compliance with the Outer Space Treaty of 1967, Lewicki said.
But there’s still some confusion in the wider world about the nascent industry and the rights of its players, so he’s happy that the U.S. Congress is taking up the asteroid-mining issue. (The House of Representatives recently passed a bill recognizing asteroid miners’ property rights, and the Senate is currently considering the legislation as well.)
“I think it’s more of a protection issue than it is an actual legal issue,” Lewicki said. “From a lawyer’s interpretation, I think the landscape is clear enough. But from an international aspect, and some investors — I think they would like to see more certainty.”
Now researchers have found that silica-rich rock much like the continental crust on Earth may be widespread at the site where Curiosity landed on Mars in August 2012.
“Mars is supposed to be a basalt-covered world,” study lead author Violaine Sautter, a planetary scientist at France’s Museum of Natural History in Paris, told Space.com. The findings are “quite a surprise,” she added.
Sautter and her colleagues analyzed data from 22 rocks probed by Curiosity as the six-wheeled robot wandered ancient terrain near Gale Crater. This 96-mile-wide (154 kilometers) pit formed about 3.6 billion years ago when a meteor slammed into Mars, and the age of the rocks from this area suggests they could help shed light on the earliest period of the Red Planets, scientists said.
The 22 rocks the researchers investigated were light-colored, contrasting with the darker basaltic rock found in younger regions on Mars. They probed these rocks using the rock-zapping laser called ChemCamon Curiosity, which analyzes the light emitted by zapped materials to determine the chemistry of Martian rocks.
The scientists found these light-colored rocks were rich in silica. A number of these were similar in composition to some of Earth’s oldest preserved continental crust.
Sautter noted that recent orbiter and rover missions had also spotted isolated occurrences of silica-rich rock. The researchers suggest these silica-rich rocks might be widespread remnants of an ancient crust on Mars that was analogous to Earth’s early continental crust and is now mostly buried under basalt.
The researchers added that the early geological history of Mars might be much more similar to that of Earth than previously thought. Future research could investigate whether the marked differences between Mars’ smooth northern hemisphere and rough, heavily cratered southern hemisphere might be due to plate tectonics, Sautter said.
The scientists detailed their findings online Monday (July 13) in the journal Nature Geoscience.
A heavyweight black hole in the heart of a distant galaxy has the mass of 140 million suns, according to new measurements. A vivid video by the National Radio Astronomy Observatory describes how researchers “weighed” the black hole at the center of the barred spiral galaxy NGC 1097.
Many galaxies have huge black holes in their centers, and these objects affect the galaxies’ growth and evolution. The galaxy NGC 1097 is 47 million light-years away from Earth, too far to determine the mass of its central black hole by the movement of the stars around it. But by tracking the movements of two types of molecular gases around the galaxy’s center, researchers using the Atacama Large Millimeter/submillimeter Array in Chile (ALMA) were able to work backward and figure out the black hole’s gravitational pull.
The ALMA telescopes tracked the radiation emitted from the two gases, hydrogen cyanide and formyl cation, as they swirled around the galaxy. The gases don’t interact strongly with environmental conditions within the galaxy, such as ionized gas flowing inward or outward. This means the gases paint an accurate picture of the effects of gravity’s pull alone. With just two hours of observational data, the researchers learned enough about the distribution and velocities of those gases to fit them to a model and calculate the pull of the galaxy’s core black hole.
The mass of a central black hole affects the physical properties of its host galaxy, and recent work has shown that those effects are different for different types of galaxies, study lead author, Kyoko Onishi, a doctoral student at the SOKENDAI (The Graduate University for Advanced Studies) in Japan, said in a statement. To understand those effects, Onishi said it’s important to measure the mass of these central black holes in various galaxy types.
Because of the quick precision measurements, “ALMA will enable us to observe a large number of galaxies in a practical length of time,” added Onishi, who is doing her research at the National Astronomical Observatory of Japan (NAOJ).