Meteorites Reveal Story Of Martian Climate

Liquid water is not stable on Mars’ surface because the planet’s atmosphere is too thin and temperatures are too cold. However, at one time Mars hosted a warm and wet surface environment that may have been conducive to life. A significant unanswered question in planetary science is when Mars underwent this dramatic change in climate conditions.

New research by Lawrence Livermore National Laboratory (LLNL) cosmochemist Bill Cassata shows that, by looking at trapped gasses in ancient Martian meteorites, the timing and effectiveness of atmospheric escape processes that have shaped Mars’ climate can be pinned down. The research appears in Earth and Planetary Science Letters.

Cassata analyzed the Martian atmospheric gas xenon (Xe, in two ancient Martian meteorites, ALH 84001 and NWA 7034. The data indicate that early in Martian history there was a sufficient concentration of atmospheric hydrogen to mass fractionated Xe (selectively removed light isotopes) through a process known as hydrodynamic escape. However, the measurements suggest this process culminated within a few hundred million years of planetary formation (more than 4 billion years ago), and little change to the atmospheric Xe isotopic composition has occurred since this time.

This differs significantly from Earth, where Xe isotopic fractionation was a gradual process that occurred throughout much of planetary history, indicating that atmospheric dynamics on the two planets diverged early in the history of the solar system.

The fact that Xe fractionation on Mars ceased more than 4 billion years ago suggests that, on Mars, the hydrogen escape flux did not exceed the threshold required to continuously fractionate atmospheric Xe, as it did on Earth, potentially because Mars did not have sufficient atmospheric water available to generate atmospheric hydrogen via photodissociation.

“These data suggest that liquid water may not have been abundant on the Martian surface since a few hundred million years after planetary formation, and therefore Mars may has been cold and dry planet for the vast majority of its history,” Cassata said.

Iron-Rich Stars Host Shorter-Period Planets

Astronomers with the Sloan Digital Sky Survey (SDSS) have learned that the chemical composition of a star can exert unexpected influence on its planetary system—a discovery made possible by an ongoing SDSS survey of stars seen by NASA’s Kepler spacecraft, and one that promises to expand our understanding of how extrasolar planets form and evolve.

“Without these detailed and accurate measurements of the iron content of stars, we could have never made this measurement,” says Robert Wilson, a graduate student in astronomy at the University of Virginia and lead author of the paper announcing the results.

The team presented their results today at the American Astronomical Society (AAS) meeting in National Harbor, Maryland. Using SDSS data, they found that stars with higher concentrations of iron tend to host planets that orbit quite close to their host star—often with orbital periods of less than about eight days—while stars with less iron tend to host planets with longer periods that are more distant from their host star. Further investigation of this effect may help us understand the full variety of extrasolar planetary systems in our Galaxy, and shed light on why planets are found where they are.

The story of planets around sun-like stars began in 1995, when a team of astronomers discovered a single planet orbiting a sun-like star 50 light years from Earth. The pace of discovery accelerated in 2009, when NASA launched the Kepler spacecraft, a space telescope designed to look for extrasolar planets. During its four-year primary mission, Kepler monitored thousands of stars at a time, watching for the tiny dimming of starlight that indicates a planet passing in front its host star. And because Kepler looked at the same stars for years, it saw their planets over and over again, and was thus able to measure the time the planet takes to orbit its star. This information reveals the distance to from star to planet, with closer planets orbiting faster than farther ones. Thanks to Kepler’s tireless monitoring, the number of exoplanets with known orbital periods increased dramatically, from about 400 in 2009 to more than 3,000 today.

Although Kepler was perfectly designed to spot extrasolar planets, it was not designed to learn about the chemical compositions of the stars around which those planets orbit. That knowledge comes from the SDSS’s Apache Point Observatory Galactic Evolution Experiment (APOGEE), which has studied hundreds of thousands of stars all over the Milky Way Galaxy. APOGEE works by collecting a spectrum for each star—a measurement of how much light the star gives off at different wavelengths (colors) of light. Because atoms of each chemical element interact with light in their own characteristic way, a spectrum allows astronomers to determine not only which elements a star contains, but also how much—for all elements including the key element iron.

“All sun-like stars are mostly hydrogen, but some contain more iron than others,” says Johanna Teske of the Carnegie Institution for Science, a member of the research team. “The amount of iron a star contains is an important clue to how it formed and how it will evolve over its lifetime.”

By combining data from these two sources—planetary orbits from Kepler and stellar chemistry from APOGEE—astronomers have learned about the relationships between these “iron-enriched” stars and the planetary systems they hold.

“We knew that the element enrichment of a star would matter for its own evolution,” says Teske, “But we were surprised to learn that it matters for the evolution of its planetary system as well.”

The work presented today builds on previous work, led by Gijs Mulders of the University of Arizona, using a larger but less precise sample of spectra from the LAMOST-Kepler project. (LAMOST, the Large-Area Multi-Object fiber Spectroscopic Telescope, is a Chinese sky survey.) Mulders and collaborators found a similar trend—closer-in planets orbiting more iron-rich stars—but did not pin down the critical period of eight days.

“It is encouraging to see an independent confirmation of the trend we found in 2016,” says Mulders. “The identification of the critical period really shows that Kepler is the gift that keeps on giving.”

What is particularly surprising about the new result, Wilson explained, is that the iron-enriched stars have only about 25 percent more iron than the others in the sample. “That’s like adding five-eighths of a teaspoon of salt into a cupcake recipe that calls for half a teaspoon of salt, among all its other ingredients. I’d still eat that cupcake,” he says. “That really shows us how even small differences in stellar composition can have profound impacts on planetary systems.”

But even with this new discovery, astronomers are left with many unanswered questions about how extrasolar planets form and evolve, especially planets Earth-sized or slightly larger (“super-Earths”). Do iron-rich stars intrinsically form planets with shorter orbits? Or are planets orbiting iron-rich stars more likely to form farther out and then migrate to shorter period, closer-in orbits? Wilson and collaborators hope to work with other astronomers to create new models of protoplanetary disks to test both of these explanations.

“I’m excited that we still have much to learn about how the chemical compositions of stars impact their planets, particularly about how small planets form,” Teske says. “Plus, APOGEE provides many more stellar chemical abundances besides iron, so there are likely other trends buried within this rich dataset that we have yet to explore.”

Extra-Terrestrial Hypatia Stone Rattles Solar System Status Quo

In 2013, researchers announced that a pebble found in south-west Egypt, was definitely not from Earth. By 2015, other research teams had announced that the ‘Hypatia’ stone was not part of any known types of meteorite or comet, based on noble gas and nuclear probe analyses.

(The stone was named Hypatia after Hypatia of Alexandria, the first Western woman mathematician and astronomer.)

However, if the pebble was not from Earth, what was its origin and could the minerals in it provide clues on where it came from? Micro-mineral analyses of the pebble by the original research team at the University of Johannesburg have now provided unsettling answers that spiral away from conventional views of the material our solar system was formed from.

Mineral structure

The internal structure of the Hypatia pebble is somewhat like a fruitcake that has fallen off a shelf into some flour and cracked on impact, says Prof Jan Kramers, lead researcher of the study published in Geochimica et Cosmochimica Acta on 28 Dec 2017.

“We can think of the badly mixed dough of a fruit cake representing the bulk of the Hypatia pebble, what we called two mixed ‘matrices’ in geology terms. The glace cherries and nuts in the cake represent the mineral grains found in Hypatia ‘inclusions’. And the flour dusting the cracks of the fallen cake represent the ‘secondary materials’ we found in the fractures in Hypatia, which are from Earth,” he says.

The original extraterrestrial rock that fell to Earth must have been at least several meters in diameter, but disintegrated into small fragments of which the Hypatia stone is one.

Weird matrix

Straight away, the Hypatia mineral matrix (represented by fruitcake dough), looks nothing like that of any known meteorites, the rocks that fall from space onto Earth every now and then.

“If it were possible to grind up the entire planet Earth to dust in a huge mortar and pestle, we would get dust with on average a similar chemical composition as chondritic meteorites,” says Kramers. “In chondritic meteorites, we expect to see a small amount of carbon{C} and a good amount of silicon (Si). But Hypatia’s matrix has a massive amount of carbon and an unusually small amount of silicon.”

“Even more unusual, the matrix contains a high amount of very specific carbon compounds, called polyaromatic hydrocarbons, or PAH, a major component of interstellar dust, which existed even before our solar system was formed. Interstellar dust is also found in comets and meteorites that have not been heated up for a prolonged period in their history,” adds Kramers.

In another twist, most (but not all) of the PAH in the Hypatia matrix has been transformed into diamonds smaller than one micrometer, which are thought to have been formed in the shock of impact with the Earth’s atmosphere or surface. These diamonds made Hypatia resistant to weathering so that it is preserved for analysis from the time it arrived on Earth.

Weirder grains never found before

When researcher Georgy Belyanin analyzed the mineral grains in the inclusions in Hypatia, (represented by the nuts and cherries of a fruitcake), a number of most surprising chemical elements showed up.

“The aluminum occurs in pure metallic form, on its own, not in a chemical compound with other elements. As a comparison, gold occurs in nuggets, but aluminum never does. This occurrence is extremely rare on Earth and the rest of our solar system, as far as is known in science,” says Belyanin.

“We also found silver iodine phosphide and moissanite (silicon carbide) grains, again in highly unexpected forms. The grains are the first documented to be found in situ (as is) without having to first dissolve the surrounding rock with acid,” adds Belyanin. “There are also grains of a compound consisting of mainly nickel and phosphorus, with very little iron; a mineral composition never observed before on Earth or in meteorites,” he adds.

Dr Marco Andreoli, a Research Fellow at the School of Geosciences at the University of the Witwatersrand, and a member of the Hypatia research team says, “When Hypatia was first found to be extraterrestrial, it was a sensation, but these latest results are opening up even bigger questions about its origins.”

Unique minerals in our solar system

Taken together, the ancient unheated PAH carbon as well as the phosphides, the metallic aluminum, and the moissanite suggest that Hypatia is an assembly of unchanged pre-solar material. That means, matter that existed in space before our Sun, the Earth and the other planets in our solar system were formed.

Supporting the pre-solar concept is the weird composition of the nickel-phosphorus-iron grains found in the Hypatia inclusions. These three chemical elements are interesting because they belong to the subset of chemical elements heavier than carbon and nitrogen which form the bulk of all the rocky planets.

“In the grains within Hypatia the ratios of these three elements to each other are completely different from that calculated for the planet Earth or measured in known types of meteorites. As such these inclusions are unique within our solar system,” adds Belyanin.

“We think the nickel-phosphorus-iron grains formed pre-solar, because they are inside the matrix, and are unlikely to have been modified by shock such as collision with the Earth’s atmosphere or surface, and also because their composition is so alien to our solar system,” he adds.

“Was the bulk of Hypatia, the matrix, also formed before our solar system? Probably not, because you need a dense dust cloud like the solar nebula to coagulate large bodies” he says.

A different kind of dust

Generally, science says that our solar system’s planets ultimately formed from a huge, ancient cloud of interstellar dust (the solar nebula) in space. The first part of that process would be much like dust bunnies coagulating in an unswept room. Science also holds that the solar nebula was homogenous, that is, the same kind of dust everywhere.

But Hypatia’s chemistry tugs at this view. “For starters, there are no silicate minerals in Hypatia’s matrix, in contrast to chondritic meteorites (and planets like the Earth, Mars and Venus), where silicates are dominant. Then there are the exotic mineral inclusions. If Hypatia itself is not presolar, both features indicate that the solar nebula wasn’t the same kind of dust everywhere — which starts tugging at the generally accepted view of the formation of our solar system,” says Kramers.

Into the future

“What we do know is that Hypatia was formed in a cold environment, probably at temperatures below that of liquid nitrogen on Earth (-196 Celsius). In our solar system it would have been way further out than the asteroid belt between Mars and Jupiter, where most meteorites come from. Comets come mainly from the Kuiper Belt, beyond the orbit of Neptune and about 40 times as far away from the sun as we are. Some come from the Oort Cloud, even further out. We know very little about the chemical compositions of space objects out there. So our next question will dig further into where Hypatia came from,” says Kramers.

The little pebble from the Libyan Desert Glass strewn field in south-west Egypt presents a tantalizing piece for an extraterrestrial puzzle that is getting ever more complex.

The research was funded by University of Johannesburg Research council via the PPM Research Centre.

Black Hole Research Could Aid Understanding Of How Small Galaxies Evolve

Scientists have solved a cosmic mystery by finding evidence that supermassive black holes prevent stars forming in some smaller galaxies.

These giant black holes are over a million times more massive than the Sun and sit in the centre of galaxies sending out powerful winds that quench the star-making process. Astronomers previously thought they had no influence on the formation of stars in dwarf galaxies but a new study from the University of Portsmouth has proved their role in the process.

The results, presented today at a meeting of the American Astronomical Society, are particularly important because dwarf galaxies (those composed of up to 100 million to several billion stars) are far more numerous than bigger systems and what happens in these is likely to give a more typical picture of the evolution of galaxies.

“Dwarf galaxies outnumber larger galaxies like the Milky Way 50 to one,” says lead researcher Dr Samantha Penny, of the University’s Institute of Cosmology and Gravitation. “So if we want to tell the full story of galaxies, we need to understand how dwarf systems work.”

In any galaxy stars are born when clouds of gas collapse under the force of their own gravity. But stars don’t keep being born forever — at some point star formation in a galaxy shuts off. The reason for this differs in different galaxies but sometimes a supermassive black hole is the culprit.

Supermassive black holes can regulate their host galaxy’s ability to form new stars through a heating process. The black hole drives energy through powerful winds. When this wind hits the giant molecular clouds in which stars would form, it heats the gas, preventing its collapse into new stars.

Previous research has shown that this process can prevent star formation in larger galaxies containing hundreds of billions of stars — but it was believed a different process could be responsible for dwarf galaxies ceasing to produce stars. Scientists previously thought that the larger galaxies could have been interacting gravitationally with the dwarf systems and pulling the star-making gas away.

Data, however, showed the researchers that the dwarf galaxies under observation were still accumulating gas which should re-start star formation in a red, dead galaxy but wasn’t. This led the team to the supermassive black hole discovery.

Dr Penny said: “Our results are important for astronomy because they potentially impact how we understand galaxy evolution. Supermassive black holes weren’t thought to influence dwarf systems but we’ve shown that isn’t the case. This may well have a big influence on future research as simulations of galaxy formation don’t usually include the heating effect of supermassive black holes in low-mass galaxies, including the dwarf systems we have examined in this work.”

The team of international scientists used data from the Sloan Digital Sky Survey (SDSS), which has a telescope based in New Mexico, to make their observations. Using SDSS’s Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, they were able to map the processes acting on the dwarf galaxies through the star systems’ heated gas, which could be detected. The heated gas revealed the presence of a central supermassive black hole, or active galactic nucleus (AGN), and through MaNGA the team were able to observe the effect that the AGN had on their host dwarf galaxies.

Kadovor Islanders evacuated

Close to six hundred Kadovar islanders in East Sepik Province have been evacuated from the island.

East Sepik Governor Allan Bird says the people have been moved to nearby Ruprup Island.

Mr Bird commended two councilors on the Island who had organized the evacuation over the weekend.

“Two very good local leaders organized the entire evacuation on the island.

They managed to evacuate 591 men,women and children without any outside assistance.

“So I want to make special mention of those two for their leadership on the ground and for the cooperation that everyone was able to show which resulted with no casualties.

The evacuation follows a renewed spewing of smoke and ash last Friday, from the volcano on the island that has been dormant for many years.

Meantime Governor Bird, says food and water supplies will be delivered to the evacuated islanders.

He says with close to 600 evacuated from Kadovar Island plus those on Ruprup, the Government will need to feed approximately 2000 people.

“There’s food been organized by the prime minister’s department.

“They’ve run out of water on Ruprup because the 1,300 people on Ruprup, that island can only support the certain number of people, and in about the last 5 or 6 days with all 600 odd people from Kadowar, food and water has already run out on the island so our immediate priority is to try to get the landing craft out there with food and water within the next 24 hours and we are working on that now.

“We are hoping to get enough food for say 2000 people for maybe two weeks.

And within that time we have to come up with an action plan to evacuate all three islands.”

Plans are underway to have islanders on the Schouten Islands in East Sepik Province permanently resettled along the coast of Turubu.

Governor Allan Bird says this will include Kadovar, Ruprup and Biem, which are all volcanic islands.

Mr Bird adds that the Provincial Administration and relevant stakeholders are now working on a relocation plan to have these group of islanders moved to the safety of Turubu, east of Wewak town.

“The advise from the Rabaul Volcano Observatory is that given the shallowness of the area and the type of volcano that Kadovar is, it is likely to cause a tsunami when it explodes.

“Given the over population of the island the plan is to relocate to the coast on the mainland at Turubu.

“Turubu is ideal because its not heavily populated, the people on the Schouten Islands have traditional ties with the people on the mainland for a long, long time, and there’s already some agreement and surveys done about moving the Schouten Islands people to the mainland.”

Earthquakes As A Driver For The Deep-Ocean Carbon Cycle

An international team led by geologist Michael Strasser has used novel methods to analyze sediment deposits in the Japan Trench in order to gain new insights into the carbon cycle.

In a paper recently published in Nature Communications, geologist Michael Strasser presented the initial findings of a month-long research expedition off the coast of Japan. The research initiative had been organised in March 2012 by MARUM – Center for Marine Environmental Sciences. Strasser, who until 2015 was Assistant Professor for Sediment Dynamics at ETH Zurich and is now a Full Professor for Sediment Geology at the University of Innsbruck, took an international team there to study dynamic sediment remobilisation processes triggered by seismic activity.

At a depth of 7,542 metres below sea level, the team took a core sample from the Japan Trench, an 800-km-long oceanic trench in the northwestern part of the Pacific Ocean. The trench, which is seismically active, was the epicentre of the Tohoku earthquake in 2011, which made headlines when it caused the nuclear meltdown at Fukushima. Such earthquakes wash enormous amounts of organic matter from the shallows down into deeper waters. The resulting sediment layers can thus be used later to glean information about the history of earthquakes and the carbon cycle in the deep ocean.

New dating methods in the deep ocean

The current study provided the researchers with a breakthrough. They analysed the carbon-rich sediments using radiocarbon dating. This method – measuring the amount of organic carbon as well as radioactive carbon (14C) in mineralised compounds – has long been a means of determining the age of individual sediment layers. Until now, however, it has not been possible to analyse samples from deeper than 5,000 metres below the surface, because the mineralised compounds dissolve under increased water pressure.

Strasser and his team therefore had to use new methods for their analysis. One of these was what is known as the online gas radiocarbon method, developed by ETH doctoral student Rui Bao and the Biogeoscience Group at ETH Zurich. This greatly increases efficiency, since it takes just a single core sample to make more than one hundred 14C age measurements directly on the organic matter contained within the sediment.

In addition, the researchers applied the Ramped PyrOx measurement method (pyrolysis) for the first time in the dating of deep-ocean sediment layers. This was done in cooperation with the Woods Hole Oceanographic Institute (U.S.), which developed the method. The process involves burning organic matter at different temperatures. Because older organic matter contains stronger chemical bonds, it requires higher temperatures to burn. What makes this method novel is that the relative age variation of the individual temperature fractions between two samples very precisely distinguishes the age difference between sediment levels in the deep sea.

Dating earthquakes to increase forecast accuracy

Thanks to these two innovative methods, the researchers could determine the relative age of organic matter in individual sediment layers with a high degree of precision. The core sample they tested contained older organic matter in three places, as well as higher rates of carbon export to the deep ocean. These places correspond to three historically documented yet hitherto imprecisely dated seismic events in the Japan Trench: the Tohoku earthquake in 2011, an unnamed earthquake in 1454, and the Sanriku earthquake in 869.

At the moment, Strasser is working on a large-scale geological map of the origin and frequency of sediments in deep-ocean trenches. To do so, he is analysing multiple core samples taken during a follow-up expedition to the Japan Trench in 2016. “The identification and dating of tectonically triggered sediment deposits is also important for future forecasts about the likelihood of earthquakes,” Strasser says. “With our new methods, we can predict the recurrence of earthquakes with much more accuracy.”

Large 7.6 Earthquake Hits Honduras; Tsunami Warning Issued

A 7.6-magnitude earthquake struck off the coast of Honduras, according to the U.S. Geological Survey.

The powerful quake struck about 125.4 miles north, northeast of the coast of Barra Patucca, Honduras. So far, there have been no immediate reports of damage.

The Pacific Tsunami Warning Center issued a tsunami advisory for Puerto Rico and the Virgin Islands.

The earthquake was initially recorded as a 7.8 magnitude, but then downgraded to 7.6 by USGS.

No further information was immediately available.