Breathable atmospheres may be more common in the universe than we first thought

The existence of habitable alien worlds has been a mainstay of popular culture for more than a century. In the 19th century, astronomers believed that Martians might be using canal-based transport links to traverse the red planet. Now, despite living in an age when scientists can study planets light years from our own solar system, most new research continues to diminish the chances of finding other worlds on which humans could live. The biggest stumbling block may be oxygen - human settlers would need a high oxygen atmosphere in which to breathe. So how were we so lucky to evolve on a planet with plenty of oxygen? The history of Earth's oceans and atmosphere suggests that the rise to present-day levels of O2 was pretty difficult. The current consensus is that Earth underwent a three-step rise in atmospheric and oceanic oxygen levels, the first being called the "Great Oxidation Event" at around 2.4 billion years ago. After that came the "Neoproterozoic Oxygenation Event" around 800 million years ago, and then finally the "Paleozoic Oxygenation Event" about 400 million years ago, when oxygen levels on Earth reached their modern peak of 21%. What happened during these three periods to increase oxygen levels is a matter for debate. One idea is that new organisms "bioengineered" the planet, restructuring the atmosphere and oceans through either their metabolisms or their lifestyles.

For example, the rise of land plants roughly 400 million years ago could have increased oxygen in the atmosphere through land-based photosynthesis, taking over from photosynthetic bacteria in the ocean which have been the main oxygen producers for most of Earth's history. Alternatively, plate tectonic changes or gigantic volcanic eruptions have also been linked to the Earth's oxygenation events.

This event-based history of how oxygen came to be so plentiful on Earth implies that we're very fortunate to be living on a high-oxygen world. If one volcanic eruption hadn't happened, or a certain type of organism hadn't evolved, then oxygen might have stalled at low levels.

But our latest research suggests that this isn't the case. We created a computer model of the Earth's carbon, oxygen and phosphorus cycles and found that the oxygen transitions can be explained by the inherent dynamics of our planet and likely didn't require any miraculous events.

Phosphorus - University of Leeds
One thing we think is missing from theories about Earth's oxygenation is phosphorus. This nutrient is very important for photosynthetic bacteria and algae in the ocean. How much marine phosphorous there is will ultimately control how much oxygen is produced on Earth. This is still true today - and has been so since the evolution of photosynthetic microbes some three billion years ago.

Photosynthesis in the ocean depends on phosphorus, but high phosphate levels also drive consumption of oxygen in the deep ocean through a process called eutrophication. When photosynthetic microbes die, they decompose, which consumes oxygen from the water. As oxygen levels fall, sediments tend to release even more phosphorus. This feedback loop rapidly removes oxygen. This meant that oxygen levels in the oceans were able to change rapidly, but they were buffered over long timescales by another process involving the Earth's mantle.

Throughout Earth's history, volcanic activity has released gases that react with and remove oxygen from the atmosphere. These gas fluxes have subsided over time due to Earth's mantle cooling, and our computer model suggests this slow reduction along with the initial evolution of photosynthetic life was all that was necessary to produce a series of step-change increases in oxygen levels.

These stepped increases bear a clear resemblance to the three-step rise in oxygen that has occurred throughout Earth's history. The model also supports our current understanding of ocean oxygenation, which appears to have involved numerous cycles of oxygenation and deoxygenation before the oceans became resiliently oxygenated as they are today.

What is really exciting about all of this is that the oxygenation pattern can be created without the need for difficult and complex evolutionary leaps forward, or circumstantial catastrophic volcanic or tectonic events. So it appears that Earth's oxygenation may have been inescapable once photosynthesis had evolved - and the chances of high oxygen worlds existing elsewhere could be much higher.

New study suggests possibility of recent underground volcanism on Mars

A study published last year in the journal Science suggested liquid water is present beneath the south polar ice cap of Mars. Now, a new study in the AGU journal Geophysical Research Letters argues there needs to be an underground source of heat for liquid water to exist underneath the polar ice cap. The new research does not take sides as to whether the liquid water exists. Instead, the authors suggest recent magmatic activity - the formation of a magma chamber within the past few hundred thousand years - must have occurred underneath the surface of Mars for there to be enough heat to produce liquid water underneath the kilometer-and-a-half thick ice cap. On the flip side, the study's authors argue that if there was not recent magmatic activity underneath the surface of Mars, then there is not likely liquid water underneath the ice cap. "Different people may go different ways with this, and we're really interested to see how the community reacts to it," said Michael Sori, an associate staff scientist in the Lunar and Planetary Laboratory at the University of Arizona and a co-lead author of the new paper. The potential presence of recent underground magmatic activity on Mars lends weight to the idea that Mars is an active planet, geologically speaking. That fact could give scientists a better understanding of how planets evolve over time. The new study is intended to further the debate around the possibility of liquid water on Mars. The presence of liquid water on the Red Planet has implications for potentially finding life outside of Earth and could also serve as a resource for future human exploration of our neighboring planet.

"We think that if there is any life, it likely has to be protected in the subsurface from the radiation," said Ali Bramson, a postdoctoral research associate at the Lunar and Planetary Laboratory at the University of Arizona and a co-lead author of the new paper. "If there are still magmatic processes active today, maybe they were more common in the recent past, and could supply more widespread basal melting. This could provide a more favorable environment for liquid water and thus, perhaps, life."

Examining the environment

Mars has two giant ice sheets at its poles, both a couple of kilometers thick. On Earth, it is common for liquid water to be present underneath thick ice sheets, with the planet's heat causing the ice to melt where it meets the Earth's crust.

In a paper published last year in Science, scientists said they detected a similar phenomenon on Mars. They claimed radar observations detected evidence of liquid water at the base of Mars's south polar ice cap. However, the Science study did not address how the liquid water could have gotten there.

Mars is much cooler than Earth so it was unclear what type of environment would be needed to melt the ice at the base of the ice cap. Although previous research has examined if liquid water could exist at the base of Mars's ice caps, no one had yet looked at the specific location where the Science study claimed to have detected water.

"We thought there was a lot of room to figure out if [the liquid water] is real, what sort of environment would you need to melt the ice in the first place, what sort of temperatures would you need, what sort of geological process would you need? Because under normal conditions, it should be too cold," Sori said.

Looking for the heat

The new study's authors first assumed the detection of liquid water underneath the ice cap was correct and then worked to figure out what parameters were needed for the water to exist. They performed physical modeling of Mars to understand how much heat is coming out of the interior of the planet and if there could be enough salt at the base of the ice cap to melt the ice. Salt lowers the melting point of ice significantly so it was thought that salt could have led to melting at the base of the ice cap.

The model showed salt alone would not raise the temperature high enough to melt the ice. Instead, the authors propose there needs to be additional heat coming from Mars's interior.

One plausible heat source would be volcanic activity in the planet's subsurface. The study's authors argue that magma from the deep interior of Mars rose towards the planet's surface about 300,000 years ago. It did not break the surface, like a volcanic eruption, but pooled in a magma chamber below the surface. As the magma chamber cooled, it released heat that melted the ice at the base of the ice sheet. The magma chamber is still providing heat to the ice sheet to generate liquid water today.

The idea of volcanic activity on Mars is not new - there is a lot of evidence of volcanism on the planet's surface. But most of the volcanic features on Mars are from millions of years ago, leading scientists to believe volcanic activity below and above the planet's surface stopped long ago.

The new study, however, proposes that there could have been more recent underground volcanic activity. And, if there was volcanic activity happening hundreds of thousands of years ago, there's a possibility it could be happening today, according to the study's authors.

"This would imply that there is still active magma chamber formation going on in the interior of Mars today and it is not just a cold, sort of dead place, internally," Bramson said.

Jack Holt, a professor at the at the Lunar and Planetary Laboratory at the University of Arizona, said the question of how water could exist underneath the south polar ice cap immediately came to his mind after the Science paper was published, and the new paper adds an important constraint on the possibility of water being there. He said it will likely add to the debate in the planetary science community about the finding and point out that more research needs to be done to evaluate it.

"I think it was a great idea to do this type of modeling and analysis because you have to explain the water, if it's there, and so it's really a critical piece of the puzzle," said Holt, who was not involved in the new research but did talk to the study's authors before they submitted the paper. "The original paper just left it hanging. There could be water there, but you have to explain it, and these guys did a really nice job of saying what is required and that salt is not sufficient."

Chandra X-ray Observatory goes into safe mode

It's been a bad couple weeks in space. A week ago, technical difficulties forced engineers to put the Hubble Space Telescope's science mission on hold. Now, the Chandra X-ray Observatory is in safe mode, too. In a statement released on Friday, NASA confirmed Chandra, one of the most powerful telescopes in space, transitioned to safe mode earlier this week. During safe mode, the observatory's mirrors are pointed away from the sun and its solar panels are turned directly toward the sun. The satellite's most critical hardware is transferred to backup drives. "Analysis of available data indicates the transition to safe mode was normal behavior for such an event," according to NASA. "All systems functioned as expected and the scientific instruments are safe." Engineers are still working to determine why Chandra went into safe mode. As Chandra's Twitter account reminded readers, the powerful X-ray telescope is getting up its in age: "Chandra is 19 years old, which is well beyond the original design lifetime of 5 years." In a separate release, NASA confirmed Hubble is still in safe mode. Last week, NASA and European Space Agency engineers suspended the telescopes' scientific activities after one of its gyroscopes failed. Scientists turned on a replacement gyro, but the backup didn't perform as hoped.

"This past week, tests were conducted to assess the condition of that backup gyro. The tests showed that the gyro is properly tracking Hubble's movement, but the rates reported are consistently higher than the true rates," according to NASA.

Because the gyro is reading rates of changes at a greater magnitude, it can't be used to monitor smaller changes. Normally, when fixed on an observation target, Hubble's gyros operate on low-mode.

"The extremely high rates currently being reported exceed the upper limit of the gyro in this low mode, preventing the gyro from reporting the spacecraft's small movements," NASA reported.

If followup troubleshooting efforts fail, Hubble will be forced to shut down all but a single gyroscope. Previous tests showed Hubble can conduct observation using a single gyro.

Hubble and Chandra aren't the only spacecraft in trouble. Earlier this week, NASA astronaut Nick Hague and Roscosmos cosmonaut Alexey Ovchinin were forced to abort their mission to the space station just moments after launch, ejecting their Soyuz capsule from the rocket and executing an emergency "ballistic descent."

And as NASA reported this week, the Mars rover Opportunity is still silent. Engineers haven't communicated with the rover for four months.

Construction of Europe's exoplanet hunter Plato begins

The construction of ESA's Plato mission to find and study planets beyond our Solar System will be led by Germany's OHB System AG as prime contractor, marking the start of the full industrial phase of the project. The announcement was made this week at the 69th International Astronautical Congress in Bremen, Germany, where the contract was formally signed. The contract covers the delivery of the satellite, including the testing phase leading to launch, support during the launch campaign, and the in-orbit commissioning phase. Plato, the PLAnetary Transits and Oscillations of stars mission, will be launched in 2026 to find and study extrasolar planetary systems, with a special emphasis on rocky planets around Sun-like stars and their habitable zone - the distance from a star where liquid water can exist on a planet's surface. "Does a second Earth exist in the Universe? is one of the exciting questions in astrophysics today," says Johann-Dietrich Worner, Director General of ESA. "With our Plato satellite we are focusing on Earth-like planets orbiting up to the habitable zone around other stars which are similar to our Sun. This will be a major step towards finding another Earth." The spacecraft will be built and assembled by OHB together with Thales Alenia Space (France and the UK) and RUAG Space Switzerland; many ESA member States will also be involved in the construction of this European planet hunter.

The German Aerospace Center (DLR) and a consortium of various European research centers and institutes will provide the scientific instrument, consisting of an array of 26 cameras and electronic units, that will observe a large patch of the sky on the lookout for planets.

"Plato is a next-generation exoplanet mission that will monitor thousands of bright stars over a large area of the sky in search of tiny, regular dips in their brightness caused by transiting planets," says Ana Heras, Plato project scientist at ESA.

"Since planets only block a minute portion of the light radiated by their parent star, this quest requires extremely precise, long-term photometric observations."

Plato will not only seek new planets but will also investigate the properties of their host stars, and determine the planetary masses, sizes and ages with unprecedented accuracy. This will help scientists understand the architecture of exoplanet systems and determine whether they might host habitable worlds. In addition, Plato will also perform asteroseismology - the study of seismic activity of stars - providing insight into stellar interiors and evolution.

The mission will expand on the work of Cheops, ESA's upcoming exoplanet watcher, which will be launched next year to perform a first characterisation of known planets. It will be followed by Ariel, scheduled for launch in 2028, which will observe a large and diverse sample of exoplanets to study their atmospheres in great detail.

Plato will operate from the 'L2' virtual point in space 1.5 million km beyond Earth as seen from the Sun. From this vantage point, it will be our outpost to unravel the mysteries of a multitude of extrasolar worlds.

"We are pleased to kick off construction of this exciting mission," says Filippo Marliani, ESA's Plato Project Manager.

"With the prime contractor and the support of European space industry, we are looking forward to building a spacecraft that will tackle some of humankind's most profound questions."

SwRI scientists study Saturn's rings to discover downpour

Using some of the Cassini spacecraft's final measurements, Southwest Research Institute scientists have discovered that complex organics rain down from Saturn's rings into its upper atmosphere. Cassini's final orbits allowed instruments to sample particles in the ring environment, discovering that the inflow of water and other material is much heavier than expected. "For its final adventure, Cassini dove into the unknown region between Saturn's rings and its atmosphere," said SwRI's Dr. Kelly Miller, who coauthored the paper "Chemical interactions between Saturn's atmosphere and its rings" published Oct. 4 in the journal Science. "Based on previous work, scientists expected water was raining from the rings into Saturn's atmosphere, so the spacecraft used its radio antenna as an umbrella to protect it from debris." After almost 20 years in space and 13 years in the Saturn system, the Cassini spacecraft was running out of fuel. NASA decided to use its last orbits to skim the upper atmosphere and skirt the edge of the inner rings before taking its final destructive dive into the planet's atmosphere in September 2017. Those final 22 orbits allowed instruments to measure the composition of Saturn's upper atmosphere and its chemical interactions with material originating in the rings.

"Turns out, ring rain is more like a ring downpour," said SwRI's Dr. Hunter Waite, the paper's lead author and principal investigator of Cassini's Ion and Neutral Mass Spectrometer (INMS). "While INMS was designed to investigate gases, we were able to measure the ring particles because they hit the spacecraft at such high velocities they vaporized. Water ice, along with the newly discovered organic compounds, is falling out of the rings way faster than anyone thought - as much as 10,000 kilograms of material per second."

"Molecular hydrogen was, as expected, the most abundant atmospheric constituent," Miller said. "But the downpour coming from the rings included plenty of water as well as molecules like butane and propane - the kind of chemicals you might use for a grill or camping stove."

The high speed of the Cassini spacecraft relative to Saturn's atmosphere allowed INMS to measure the ring particles, but it also complicated the interpretation of the data. Molecules and particles would likely shatter upon impact with the detector so the various organic compounds detected by INMS are likely fragments. The observations also show evidence for variations from one spacecraft orbit to the next in the relative abundances of infalling material, suggesting that regions in Saturn's innermost D ring are materially variable, either over time or by locality.

"While INMS was one of the last instruments collecting data to the mission's end, getting these results was not easy," said SwRI's Rebecca Perryman, INMS operations lead and the paper's second author. The team spent months processing, examining and reexamining the data.

"It was worth it. The large mass of infalling material has implications for ring evolution, hinting that material from the C ring repeatedly replenishes the neighboring D ring," Waite said. "This infalling material likely affects the atmospheric chemistry and the carbon content of Saturn's ionosphere and atmosphere."

Astrophysicists measure precise rotation pattern of Sun-like stars for the first time

Sun-like stars rotate up to two and a half times faster at the equator than at higher latitudes, a finding by researchers at NYU Abu Dhabi that challenges current science on how stars rotate. Until now, little was known about the precise rotational patterns of Sun-like stars, only that the equator spins faster than at higher latitudes, similar to the Sun. Scientists at the NYU Abu Dhabi Center for Space Science used observations from NASA's Kepler mission and asteroseismology - the study of sound waves traveling inside stars - to determine with precision how Sun-like stars rotate, which no other scientific method has been able to achieve. Their study found that Sun-like stars, characterized as being like the Sun in mass and age, do indeed rotate in a similar manner as the Sun in that their equatorial regions rotate more rapidly than at mid- to high latitudes. But there's a key difference.The equator of the Sun rotates about 10 percent faster than its mid latitudes, while equators of Sun-like stars spin up to two and a half times faster than their mid latitudes. "This is very unexpected, and challenges current numerical simulations, which suggest that stars like these should not be able to sustain differential rotation of this magnitude," said Othman Benomar, research associate at the NYU Abu Dhabi Center for Space Science and lead author of the study published in Science.

"Understanding differential rotation - how fast one part of a star spins compared to the rest - is not only important for a complete understanding of how a star works, it will help us gain deeper insights about their magnetic fields," explained Katepalli Sreenivasan, principal investigator of the NYU Abu Dhabi Center for Space Science.

Magnetic fields on the Sun have been known to cause enormous solar storms that frequently disrupt orbiting space satellites and have knocked out power grids on Earth.

Scientists agree that the rotation of the Sun plays a crucial role in the generation of the solar magnetic field, but the exact details still remain a mystery, despite the Sun having been observed and studied in great detail.

Sreenivasan added, "learning more about how stars rotate and generate their own magnetic fields could help us gain further insight into the solar dynamo, the physical process that generates the Sun's magnetic field."

Study of material surrounding distant stars shows Earth's ingredients 'pretty normal'

The Earth's building blocks seem to be built from 'pretty normal' ingredients, according to researchers working with the world's most powerful telescopes. Scientists have measured the compositions of 18 different planetary systems from up to 456 light years away and compared them to ours, and found that many elements are present in similar proportions to those found on Earth. This is amongst the largest examinations to measure the general composition of materials in other planetary systems, and begins to allow scientists to draw more general conclusions on how they are forged, and what this might mean for finding Earth-like bodies elsewhere. "Most of the building blocks we have looked at in other planetary systems have a composition broadly similar to that of the Earth", said researcher Dr Siyi Xu of the Gemini Observatory in Hawaii, who was presenting the work at the Goldschmidt conference in Boston. The first planets orbiting other stars were only found in 1992 (this was orbiting a pulsar), since then scientists have been trying to understand whether some of these stars and planets are similar to our own solar system. "It is difficult to examine these remote bodies directly. Because of the huge distances involved, their nearby star tends to drown out any electromagnetic signal, such as light or radio waves" said Siyi Xu. "So we needed to look at other methods".

Because of this, the team decided to look at how the planetary building blocks affect signals from white dwarf stars. These are stars which have burnt off most of their hydrogen and helium, and shrunk to be very small and dense - it is anticipated that our Sun will become a white dwarf in around 5 billion years.

Dr Xu continued, "White dwarfs' atmospheres are composed of either hydrogen or helium, which give out a pretty clear and clean spectroscopic signal. However, as the star cools, it begins to pull in material from the planets, asteroids, comets and so on which had been orbiting it, with some forming a dust disk, a little like the rings of Saturn.

"As this material approaches the star, it changes how we see the star. This change is measurable because it influences the star's spectroscopic signal, and allows us to identify the type and even the quantity of material surrounding the white dwarf. These measurements can be extremely sensitive, allowing bodies as small as an asteroid to be detected".

The team took measurements using spectrographs on the Keck telescope in Hawaii, the world's largest optical and infrared telescope, and on the Hubble Space Telescope.

Siyi Xu continued, "In this study, we have focused on the sample of white dwarfs with dust disks. We have been able to measure calcium, magnesium, and silicon content in most of these stars, and a few more elements in some stars. We may also have found water in one of the systems, but we have not yet quantified it: it's likely that there will be a lot of water in some of these worlds. For example, we've previously identified one star system, 170 light years away in the constellation Bootes, which was rich in carbon, nitrogen and water, giving a composition similar to that of Halley's Comet. In general though, their composition looks very similar to bulk Earth.

This would mean that the chemical elements, the building blocks of earth are common in other planetary systems. From what we can see, in terms of the presence and proportion of these elements, we're normal, pretty normal. And that means that we can probably expect to find Earth-like planets elsewhere in our Galaxy".

Dr Xu continued "This work is still on-going and the recent data release from the Gaia satellite, which so far has characterized 1.7 billion stars, has revolutionized the field. This means we will understand the white dwarfs a lot better. We hope to determine the chemical compositions of extrasolar planetary material to a much higher precision"

Professor Sara Seager, Professor of Planetary Science at Massachusetts Institute of Technology, is also the deputy science director of the recently-launched TESS (Transiting Exoplanet Survey Satellite) mission, which will search for exoplanets. She said:

"It's astonishing to me that the best way to study exoplanet interiors is by planets ripped apart and absorbed by their white dwarf host star. It is great to see progress in this research area and to have solid evidence that planets with Earth-like compositions are common--fueling our confidence that an Earth-like planet around a very nearby normal star is out there waiting to be found".

NASA postpones for 24 hours launch of historic spaceship to Sun

NASA postponed until Sunday the launch of the first ever spacecraft to fly directly toward the Sun on a mission to plunge into our star's sizzling atmosphere and unlock its mysteries. The reason for the delay was not immediately clear, but was called for after a gaseous helium alarm was sounded in the last moments before liftoff, officials said. Engineers are taking utmost caution with the $1.5 billion Parker Solar Probe, which Thomas Zurbuchen, head of NASA's science mission directorate, described as one of the agency's most "strategically important missions." The next launch window opens at 3:31 am (0731 GMT) on Sunday, when weather conditions are 60 percent favorable for launch, NASA said. By coming closer to the Sun than any spacecraft in history, the unmanned probe's main goal is to unveil the secrets of the corona, the unusual atmosphere around the Sun. Not only is the corona about 300 times hotter than the Sun's surface, but it also hurls powerful plasma and energetic particles that can unleash geomagnetic space storms, wreaking havoc on Earth by disrupting the power grid. These solar outbursts are poorly understood, but pack the potential to wipe out power to millions of people.

- 'Full of mysteries' -

The probe is protected by an ultra-powerful heat shield that is 4.5 inches (11.43 centimeters) thick.

The shield should enable the spacecraft to survive its close shave with the fiery star, coming within 3.83 million miles (6.16 million kilometers) of the Sun's surface.

The heat shield is built to withstand radiation equivalent to up to about 500 times the Sun's radiation on Earth.

Even in a region where temperatures can reach more than a million degrees Fahrenheit, the sunlight is expected to heat the shield to just around 2,500 degrees Fahrenheit (1,371 degrees Celsius).

If all works as planned, the inside of the spacecraft should stay at just 85 degrees Fahrenheit.

"The sun is full of mysteries," said Nicky Fox, project scientist at the Johns Hopkins University Applied Physics Lab.

- 91-year-old namesake -

The tools on board will measure the expanding corona and continually flowing atmosphere known as the solar wind, which solar physicist Eugene Parker first described in 1958.

Parker, now 91, recalled that at first some people did not believe in his theory.

But then, the launch of NASA's Mariner 2 spacecraft in 1962 -- becoming the first robotic spacecraft to make a successful planetary encounter -- proved them wrong.

"It was just a matter of sitting out the deniers for four years until the Venus Mariner 2 spacecraft showed that, by golly, there was a solar wind," Parker said earlier this week.

Parker said he was "impressed" by the Parker Solar Probe, calling it "a very complex machine."

According to Zurbuchen, Parker is an "incredible hero of our scientific community."

"Life is all about these big arcs. Sometimes you just see, like how over a lifetime, things just come together and create these amazing stories, these leaps going forward."

Exoplanets where life could develop as on Earth

Scientists have identified a group of planets outside our solar system where the same chemical conditions that may have led to life on Earth exist. The researchers, from the University of Cambridge and the Medical Research Council Laboratory of Molecular Biology (MRC LMB), found that the chances for life to develop on the surface of a rocky planet like Earth are connected to the type and strength of light given off by its host star. Their study, published in the journal Science Advances, proposes that stars which give off sufficient ultraviolet (UV) light could kick-start life on their orbiting planets in the same way it likely developed on Earth, where the UV light powers a series of chemical reactions that produce the building blocks of life. The researchers have identified a range of planets where the UV light from their host star is sufficient to allow these chemical reactions to take place, and that lie within the habitable range where liquid water can exist on the planet's surface. "This work allows us to narrow down the best places to search for life," said Dr. Paul Rimmer, a postdoctoral researcher with a joint affiliation at Cambridge's Cavendish Laboratory and the MRC LMB, and the paper's first author. "It brings us just a little bit closer to addressing the question of whether we are alone in the universe."

The new paper is the result of an ongoing collaboration between the Cavendish Laboratory and the MRC LMB, bringing together organic chemistry and exoplanet research. It builds on the work of Professor John Sutherland, a co-author on the current paper, who studies the chemical origin of life on Earth.

In a paper published in 2015, Professor Sutherland's group at the MRC LMB proposed that cyanide, although a deadly poison, was in fact a key ingredient in the primordial soup from which all life on Earth originated.

In this hypothesis, carbon from meteorites that slammed into the young Earth interacted with nitrogen in the atmosphere to form hydrogen cyanide. The hydrogen cyanide rained to the surface, where it interacted with other elements in various ways, powered by the UV light from the Sun. The chemicals produced from these interactions generated the building blocks of RNA, the close relative of DNA which most biologists believe was the first molecule of life to carry information.

In the laboratory, Sutherland's group recreated these chemical reactions under UV lamps, and generated the precursors to lipids, amino acids and nucleotides, all of which are essential components of living cells.

"I came across these earlier experiments, and as an astronomer, my first question is always what kind of light are you using, which as chemists they hadn't really thought about," said Rimmer. "I started out measuring the number of photons emitted by their lamps, and then realised that comparing this light to the light of different stars was a straightforward next step."

The two groups performed a series of laboratory experiments to measure how quickly the building blocks of life can be formed from hydrogen cyanide and hydrogen sulphite ions in water when exposed to UV light. They then performed the same experiment in the absence of light.

"There is chemistry that happens in the dark: it's slower than the chemistry that happens in the light, but it's there," said senior author Professor Didier Queloz, also from the Cavendish Laboratory. "We wanted to see how much light it would take for the light chemistry to win out over the dark chemistry."

The same experiment run in the dark with the hydrogen cyanide and the hydrogen sulphite resulted in an inert compound which could not be used to form the building blocks of life, while the experiment performed under the lights did result in the necessary building blocks.

The researchers then compared the light chemistry to the dark chemistry against the UV light of different stars. They plotted the amount of UV light available to planets in orbit around these stars to determine where the chemistry could be activated.

They found that stars around the same temperature as our Sun emitted enough light for the building blocks of life to have formed on the surfaces of their planets. Cool stars, on the other hand, do not produce enough light for these building blocks to be formed, except if they have frequent powerful solar flares to jolt the chemistry forward step by step. Planets that both receive enough light to activate the chemistry and could have liquid water on their surfaces reside in what the researchers have called the abiogenesis zone.

Among the known exoplanets which reside in the abiogenesis zone are several planets detected by the Kepler telescope, including Kepler 452b, a planet that has been nicknamed Earth's 'cousin,' although it is too far away to probe with current technology. Next-generation telescopes, such as NASA's TESS and James Webb telescopes, will hopefully be able to identify and potentially characterise many more planets that lie within the abiogenesis zone.

Of course, it is also possible that if there is life on other planets, that it has or will develop in a totally different way than it did on Earth.

"I'm not sure how contingent life is, but given that we only have one example so far, it makes sense to look for places that are most like us," said Rimmer. "There's an important distinction between what is necessary and what is sufficient. The building blocks are necessary, but they may not be sufficient: it's possible you could mix them for billions of years and nothing happens. But you want to at least look at the places where the necessary things exist."

According to recent estimates, there are as many as 700 million trillion terrestrial planets in the observable universe. "Getting some idea of what fraction have been, or might be, primed for life fascinates me," said Sutherland. "Of course, being primed for life is not everything and we still don't know how likely the origin of life is, even given favourable circumstances - if it's really unlikely then we might be alone, but if not, we may have company."

Scientists developing guidebook for finding life beyond Earth

If you're looking for a manual on the hunt for alien life, you're in luck. Some of the leading experts in the field, including a UC Riverside team of researchers, have written a major series of review papers on the past, present, and future of the search for life on other planets. Published in Astrobiology, the papers represent two years of work by the Nexus for Exoplanet Systems Science (NExSS), a NASA-coordinated research network dedicated to the study of planetary habitability, and by NASA's Astrobiology Institute. Scientists have identified more than 3,500 planets around other stars (called exoplanets) and many more will be discovered in the coming decades. Some of these are rocky, Earth-sized planets that are in the habitable zones of their stars, meaning it's neither too hot nor too cold for liquid water - and possibly life - to exist. The five papers will serve as a reference for scientists searching for signs of life, called biosignatures, in the data they collect from future telescope observations. "In less than 30 years, we've gone from not knowing whether planets existed outside our solar system to being able to pinpoint potentially habitable planets and collect data that will enable us to look for the signatures of life," said Edward Schwieterman, a postdoctoral researcher in UCR's Department of Earth Sciences and lead author on the first paper in the series.

"These advances offer unprecedented opportunities to answer the age-old question, 'are we alone?,' but at the same time demand that we move forward with great care by developing robust models that allow us to seek and identify life with a high degree of certainty."

Schwieterman's paper reviews three types of biosignatures that astrobiologists have previously proposed as markers for life on other planets, all of which must be remotely detected since exoplanets orbit distant stars that we cannot reach in person. The markers include:

* Gaseous biosignatures - byproducts of life that can be detected in the atmosphere, such as oxygen produced by photosynthesis, as on Earth.

* Surface biosignatures - life-induced changes in the absorption and reflection of light on the surface of a planet, such as the red-edge caused when plants absorb red light during photosynthesis but reflect infrared light that is not used.

* Temporal biosignatures - time-dependent fluctuations in gaseous or surface biosignatures, such as biologically modulated changes in the Earth's atmosphere that occur during different seasons.

Schwieterman is part of UCR's NASA-funded Alternative Earths Astrobiology Center, an interdisciplinary group that is developing a "search engine" for life on other worlds by delving into our own planet's dynamic, 4.5-billion-year history. Though dramatically different in terms of atmospheric composition and climate, the different chapters of Earth's history have one thing in common: oceans teeming with a remarkable diversity of simple and complex life.

"We are using Earth to guide our search for life on other planets because it is the only known example we have," said Timothy Lyons, a distinguished professor of biogeochemistry and director of the Alternative Earths Astrobiology Center.

"But Earth actually offers us a great diversity of possibilities. Rather than being constrained to a study of present-day life, we use geological and geochemical analyses to examine the billions of years that life survived, evolved, and thrived on Earth under conditions that are very different than today's, hence the concept of 'alternative Earths.'"

Schwieterman's review outlines the complexities of searching for life on planets that are too far away to visit, including phenomena called false positives and false negatives.

"The search for life using biosignatures is not as simple as looking for a single molecule or compound. Atmospheric oxygen, for example, could be a sign of life, but there are many nonbiological ways that oxygen gas could be produced on an exoplanet. Conversely, it is possible that life could exist in the absence of oxygen gas, similar to early life on Earth or portions of the oceans today," Schwieterman said.

"This is one reason temporal biosignatures, which are based on dynamic phenomena such as atmospheric seasonality, might be more robust biosignatures in some circumstances."

More research on the ways nature can fool scientists into thinking a lifeless planet is alive or vice versa is described in the second paper in the series. The third and fourth papers propose novel investigations that would expand our conception of biosignatures to myriad habitable planets that are radically different from past or present Earth. The final article discusses how the search for life through biosignatures is incorporated into telescope and mission design.

In addition to Schwieterman and Lyons, Stephanie Olson, a graduate student in Earth Sciences, contributed to this research. The team, together with Christopher Reinhard, an assistant professor at Georgia Institute of Technology and a member of UCR-led Alternative Earths Astrobiology team, contributed to several other papers in the series.

"Together, these papers highlight UCR's contributions to the understanding of exoplanet biosignatures and the implications for instrument design going forward," Schwieterman said.

"These contributions will provide an entry point for people from disparate fields interested in how they too might contribute to the search for life outside our solar system."

New estimates of Mercury's thin, dense crust

Mercury is small, fast and close to the sun, making the rocky world challenging to visit. Only one probe has ever orbited the planet and collected enough data to tell scientists about the chemistry and landscape of Mercury's surface. Learning about what is beneath the surface, however, requires careful estimation. After the probe's mission ended in 2015, planetary scientists estimated Mercury's crust was roughly 22 miles thick. One University of Arizona scientist disagrees.Using the most recent mathematical formulas, Lunar and Planetary Laboratory associate staff scientist Michael Sori estimates that the Mercurial crust is just 16 miles thick and is denser than aluminum. His study, "A Thin, Dense Crust for Mercury," will be published May 1 in Earth and Planetary Science Letters and is currently available online. Sori determined the density of Mercury's crust using data collected by the Mercury Surface, Space Environment and Geochemistry Ranging (MESSENGER) spacecraft. He created his estimate using a formula developed by Isamu Matsuyama, a professor in the Lunar and Planetary Laboratory, and University of California Berkeley scientist Douglas Hemingway. Sori's estimate supports the theory that Mercury's crust formed largely through volcanic activity. Understanding how the crust was formed may allow scientists to understand the formation of the entire oddly structured planet.

"Of the terrestrial planets, Mercury has the biggest core relative to its size," Sori said.

Mercury's core is believed to occupy 60 percent of the planet's entire volume. For comparison, Earth's core takes up roughly 15 percent of its volume. Why is Mercury's core so large?

"Maybe it formed closer to a normal planet and maybe a lot of the crust and mantle got stripped away by giant impacts," Sori said. "Another idea is that maybe, when you're forming so close to the sun, the solar winds blow away a lot of the rock and you get a large core size very early on. There's not an answer that everyone agrees to yet."

Sori's work may help point scientists in the right direction. Already, it has solved a problem regarding the rocks in Mercury's crust.

Mercury's Mysterious Rocks

When the planets and Earth's moon formed, their crusts were born from their mantles, the layer between a planet's core and crust that oozes and flows over the course of millions of years. The volume of a planet's crust represents the percentage of mantle that was turned into rocks.

Before Sori's study, estimates of the thickness of Mercury's crust led scientists to believe 11 percent of the planet's original mantle had been turned into rocks in the crust. For the Earth's moon - the celestial body closest in size to Mercury - the number is lower, near 7 percent.

"The two bodies formed their crusts in very different ways, so it wasn't necessarily alarming that they didn't have the exact same percentage of rocks in their crust," Sori said.

The moon's crust formed when less dense minerals floated to the surface of an ocean of liquid rock that became the body's mantle. At the top of the magma ocean, the moon's buoyant minerals cooled and hardened into a "flotation crust." Eons of volcanic eruptions coated Mercury's surface and created its "magmatic crust."

Explaining why Mercury created more rocks than the moon did was a scientific mystery no one had solved. Now, the case can be closed, as Sori's study places the percentage of rocks in Mercury's crust at 7 percent. Mercury is no better than the moon at making rocks.

Sori solved the mystery by estimating the crust's depth and density, which meant he had to find out what kind of isostasy supported Mercury's crust.

Determining Density and Depth

The most natural shape for a planetary body to take is a smooth sphere, where all points on the surface are an equal distance from the planet's core. Isostasy describes how mountains, valleys and hills are supported and kept from flattening into smooth plains.

There are two main types isostasy: Pratt and Airy. Both focus on balancing the masses of equally sized slices of the planet. If the mass in one slice is much greater than the mass in a slice next to it, the planet's mantle will ooze, shifting the crust on top of it until the masses of every slice are equal.

Pratt isostasy states that a planet's crust varies in density. A slice of the planet that contains a mountain has the same mass as a slice that contains flat land, because the crust that makes the mountain is less dense than the crust that makes flat land. In all points of the planet, the bottom of the crust floats evenly on the mantle.

Until Sori completed his study, no scientist had explained why Pratt isostasy would or wouldn't support Mercury's landscape. To test it, Sori needed to relate the planet's density to its topography. Scientists had already constructed a topographic map of Mercury using data from MESSENGER, but a map of density didn't exist. So Sori made his own using MESSENGER's data about the elements found on Mercury's surface.

"We know what minerals usually form rocks, and we know what elements each of these minerals contain. We can intelligently divide all the chemical abundances into a list of minerals," Sori said of the process he used to determine the location and abundance of minerals on the surface. "We know the densities of each of these minerals. We add them all up, and we get a map of density."

Sori then compared his density map with the topographic map. If Pratt isostasy could explain Mercury's landscape, Sori expected to find high-density minerals in craters and low-density minerals in mountains; however, he found no such relationship. On Mercury, minerals of high and low density are found in mountains and craters alike.

With Pratt isostasy disproven, Sori considered Airy isostasy, which has been used to make estimates of Mercury's crustal thickness. Airy isostasy states that the depth of a planet's crust varies depending on the topography.

"If you see a mountain on the surface, it can be supported by a root beneath it," Sori said, likening it to an iceberg floating on water.

The tip of an iceberg is supported by a mass of ice that protrudes deep underwater. The iceberg contains the same mass as the water it displaces. Similarly, a mountain and its root will contain the same mass as the mantle material being displaced. In craters, the crust is thin, and the mantle is closer to the surface. A wedge of the planet containing a mountain would have the same mass as a wedge containing a crater.

"These arguments work in two dimensions, but when you account for spherical geometry, the formula doesn't exactly work out," Sori said.

The formula recently developed by Matsuyama and Hemingway, though, does work for spherical bodies like planets. Instead of balancing the masses of the crust and mantle, the formula balances the pressure the crust exerts on the mantle, providing a more accurate estimate of crustal thickness.

Sori used his estimates of the crust's density and Hemingway and Matsuyama's formula to find the crust's thickness. Sori is confident his estimate of Mercury's crustal thickness in its northern hemisphere will not be disproven, even if new data about Mercury is collected. He does not share this confidence about Mercury's crustal density.

MESSENGER collected much more data on the northern hemisphere than the southern, and Sori predicts the average density of the planet's surface will change when density data is collected over the entire planet. He already sees the need for a follow-up study in the future.

The next mission to Mercury will arrive at the planet in 2025. In the meantime, scientists will continue to use MESSENGER data and mathematical formulas to learn everything they can about the first rock from the sun.

Astrophysics CubeSat Demonstrates Big Potential in a Small Package

The ASTERIA satellite, which was deployed into low-Earth orbit in November, is only slightly larger than a box of cereal, but it could be used to help astrophysicists study planets orbiting other stars. Mission managers at NASA's Jet Propulsion Laboratory in Pasadena, California, recently announced that ASTERIA has accomplished all of its primary mission objectives, demonstrating that the miniaturized technologies on board can operate in space as expected. This marks the success of one of the world's first astrophysics CubeSat missions, and shows that small, low-cost satellites could be used to assist in future studies of the universe beyond the solar system. "ASTERIA is small but mighty," said Mission Manager Matthew W. Smith of JPL. "Packing the capabilities of a much larger spacecraft into a small footprint was a challenge, but in the end we demonstrated cutting-edge performance for a system this size." ASTERIA, or the Arcsecond Space Telescope Enabling Research in Astrophysics, weighs only 22 pounds (10 kilograms). It carries a payload for measuring the brightness of stars, which allows researchers to monitor nearby stars for orbiting exoplanets that cause a brief drop in brightness as they block the starlight.

This approach to finding and studying exoplanets is called the transit method. NASA's Kepler Space Telescope has detected more than 2,300 confirmed planets using this method, more than any other planet-hunting observatory. The agency's next large-scale, space-based planet-hunting observatory, the Transiting Exoplanet Survey Satellite (TESS), is anticipated to discover thousands of exoplanets and scheduled to launch from Cape Canaveral Air Force Station in Florida on April 16.

In the future, small satellites like ASTERIA could serve as a low-cost method to identify transiting exoplanets orbiting bright, Sun-like stars. These small satellites could be used to look for planetary transits when larger observatories are not available, and planets of interest could then be studied in more detail by other telescopes.

Small satellites like ASTERIA could also be used to study certain star systems that are not within the field of view of larger observatories, and most significantly, focus on star systems that have planets with long orbits that require long observation campaigns.

The ASTERIA team has now demonstrated that the satellite's payload can point directly and steadily at a bright source for an extended period of time, a key requirement for performing the precision photometry necessary to study exoplanets via the transit method.

Holding steady on a faraway star is difficult because there are many things that subtly push and pull on the satellite, such as Earth's atmosphere and magnetic field. ASTERIA's payload achieved a pointing stability of 0.5 arcseconds RMS, which refers to the degree to which the payload wobbles away from its intended target over a 20-minute observation period. The pointing stability was repeated over multiple orbits, with the stars positioned on the same pixels on each orbit.

"That's like being able to hit a quarter with a laser pointer from about a mile away," said Christopher Pong, the attitude and pointing control engineer for ASTERIA at JPL. "The laser beam has to stay inside the edge of the quarter, and then the satellite has to be able to hit that exact same quarter - or star - over multiple orbits around the Earth. So what we've accomplished is both stability and repeatability."

The payload also employed a control system to reduce "noise" in the data created by temperature fluctuations in the satellite, another major hurdle for an instrument attempting to carefully monitor stellar brightness. During observations, the temperature of the controlled section of the detector fluctuates by less than 0.02 Fahrenheit (0.01 Kelvin, or 0.01 degree Celsius).

Small satellites

ASTERIA is a CubeSat, a type of small satellite consisting of "units" that are 10 centimeters cubed, or about 4 inches on each side. ASTERIA is the size of six CubeSat units, making it roughly 10 centimeters by 20 centimeters by 30 centimeters. With its two solar panels unfolded, the satellite is about as long as a skateboard.

The ASTERIA mission utilized commercially available CubeSat hardware where possible, and is contributing to a general knowledge of how those components operate in space.

"We're continuing to characterize CubeSat components that other missions are using or want to use," said Amanda Donner, mission assurance manager for ASTERIA at JPL.

ASTERIA launched to the International Space Station in August 2017. Having been in space for more than 140 days, the satellite is operating on an extended mission through May.

ASTERIA was developed under the Phaeton Program at JPL. Phaeton provides early-career hires, under the guidance of experienced mentors, with the challenges of a flight project. ASTERIA is a collaboration with the Massachusetts Institute of Technology in Cambridge; where Sara Seager is the principal investigator.

Green Light for Continued Operations of ESA Science Missions

ESA's Science Programme Committee (SPC) has approved indicative extensions, up to 2019-2020, for the operation of eight scientific missions. During its meeting at ESA Headquarters in Paris, on 21-22 November, the SPC approved indicative extensions for the continued operation of five ESA-led missions: Gaia, INTEGRAL, Mars Express, SOHO, and XMM-Newton. This followed a comprehensive review of the current operational status and outlook of the missions and their expected scientific returns during the extension period. The decision will be subject to confirmation towards the end of 2018. [1] The lifetime of Gaia, ESA's billion star surveyor, was extended by eighteen months, from 25 July 2019 to 31 December 2020. This is the first time that Gaia, which was launched in 2013 and originally funded for a five-year mission, has been subject to the extension process. Mars Express, SOHO, and XMM-Newton each received extensions of two years, so their operations will continue at least until the end of 2020.

The SPC extended the operations of the high-energy observatory INTEGRAL by one year, until 31 December 2019. A proposal to extend INTEGRAL until the end of 2020, as well as a proposal concerning a two-year extension of the magnetospheric plasma mission, Cluster, will be presented to the next meeting of the SPC in February 2018.

The go-ahead was also given to continue ESA's contributions to the operations of three international collaborative missions: the Hubble Space Telescope (HST), and the Interface Region Imaging Spectrograph (IRIS), which are both led by NASA, as well as the Japanese-led mission Hinode.

[1] Every two years, all missions whose approved operations end within the following four years are subject to review by the advisory structure of the Science Directorate. Extensions are granted to missions that satisfy the established criteria for operational status and science return, subject to the level of financial resources available in the science programme. These extensions are valid for the following four years, subject to a mid-term review and confirmation after two years. Extensions for operations in the period 2017-2018 were approved by the SPC in November 2016, but the indicative extension, for 2019-2020, had been deferred until the November 2017 meeting to allow the SPC to evaluate the outcome of the ESA Ministerial Council meeting in December 2016.

NASA successfully fires Voyager 1 thrusters after 37 years

NASA's Voyager 1 spacecraft -- cruising interstellar space billions of miles from Earth -- was back on the right track Friday thanks to thrusters that were fired up for the first time in 37 years. The unmanned spaceship was launched along with its twin, Voyager 2, more than 40 years ago to explore the outer planets of our solar system, traveling further than any human-made object in history. But after decades of operation, the "attitude control thrusters" that turn the spacecraft by firing tiny "puffs" had degraded. The small adjustments are needed to turn Voyager's antenna toward Earth, allowing it to continue sending communications. "At 13 billion miles from Earth, there's no mechanic shop nearby to get a tune-up," NASA said in a news release. Experts at the agency's Jet Propulsion Laboratory in California decided to turn to four backup thrusters that were last used on November 8, 1980. "The Voyager flight team dug up decades-old data and examined the software that was coded in an outdated assembler language, to make sure we could safely test the thrusters," said Chris Jones, chief engineer at JPL. The engineers fired up the thrusters on Tuesday and tested their ability to turn Voyager using 10-millisecond pulses. Then they waited 19 hours, 35 minutes for the test results to arrive at an antenna in Goldstone, California.

Turns out the thrusters worked just fine.

"The Voyager team got more excited each time with each milestone in the thruster test. The mood was one of relief, joy and incredulity after witnessing these well-rested thrusters pick up the baton as if no time had passed at all," said Todd Barber, a JPL propulsion engineer.

Being able to use the backup thrusters means the lifespan of Voyager 1 has been extended by two or three years, added Suzanne Dodd, project manager for Voyager.

NASA plans to switch over to the formerly dormant thrusters in January. They will likely also conduct similar tests on the backup thrusters on Voyager 2.

Scientists still hear from the Voyager spacecraft daily, and expect to get data for about another decade.

Astronomy textbooks were rewritten on a wide scale thanks to the Voyager spacecraft, which zoomed past Jupiter, Saturn, Neptune and Uranus.

The plutonium-powered spaceships will continue until they finally run out of fuel, and will then orbit in the center of the Milky Way galaxy.

Crossing drones with satellites: ESA eyes high-altitude aerial platforms

ESA is considering extending its activities to a new region of the sky via a novel type of aerial vehicle, a 'missing link' between drones and satellites. High Altitude Pseudo-Satellites, or HAPS, are platforms that float or fly at high altitude like conventional aircraft but operate more like satellites - except that rather than working from space they can remain in position inside the atmosphere for weeks or even months, offering continuous coverage of the territory below. The best working altitude is about 20 km, above the clouds and jet streams, and 10 km above commercial airliners, where wind speeds are low enough for them to hold position for long periods. From such a height they can survey the ground to the horizon 500 km away, variously enabling precise monitoring and surveillance, high-bandwidth communications or back up to existing satellite navigation services. Several ESA directorates have teamed up to investigate their potential, explains future-systems specialist Antonio Ciccolella: "For Earth observation, they could provide prolonged high-resolution coverage for priority regions, while for navigation and telecoms they could shrink blind spots in coverage and combine wide bandwidth with negligible signal delay.

"ESA is looking into how these various domains can be best brought together."

Earth observation specialist Thorsten Fehr explains, "We've been looking into the concept for the last 20 years but now finally it's becoming reality.

"That's come about through the maturing of key technologies: miniaturised avionics, high-performance solar cells, lightweight batteries and harness, miniaturisation of Earth observation sensors and high-bandwidth communication links that can deliver competitively priced services."

Navigation engineer Roberto Prieto Cerdeira adds "There's obvious potential for emergency response. They could also be employed semi-permanently, perhaps extending satnav coverage into high, narrow valleys and cities."

European companies have already unveiled product lines. For instance, Airbus has developed the winged, solar-powered Zephyr, which in 2010 achieved a world record 14 days of continuous flight without refuelling.

Zephyr-S is designed to fly payloads of a few tens of kilograms for up to three months at a time, with secondary batteries employed to keep it powered and aloft overnight. A larger Zephyr-T version in preparation will support larger payloads and power needs.

Thales Alenia Space is meanwhile preparing the lighter-than-air Stratobus, with its first flight expected in 2021.

The buoyant Stratobus airship can carry up to 250 kg, its electric engines flying against the breeze to hold itself in position, relying on fuel cells at night.

Many other firms are also developing vehicles, payloads and services. Last month saw them gathered at ESA's inaugural workshop, together with representatives of potential customers, including the European Defence Agency, Frontex - the EU agency tasked with Europe's border management - and EU Copernicus environmental monitoring services.

"This was the first meeting of its kind in Europe, with more than 200 HAPS experts" explains Juan Lizarraga Cubillos, from ESA's telecoms area.

"We heard from them on the needs, opportunities and critical issues within the field, particularly as a complement for existing satellite services, to start preparing a future ESA programme." ESA regards the vehicles as a valuable way of establishing applications that complement its satellites while also accelerating space technologies through early, high-altitude flight testing.

The point was also made that market acceptance of HAPS would come down to their efficiency and cost-effectiveness - and the best way to show that would be through demonstration projects.

"We have to fly them," remarked Alvaro Rodriquez of the EU's Satellite Centre. "The technology is there, all the ingredients are there, now it's time to mix them into a nice recipe."

Measuring neutron star sizes by using thermonuclear explosion models

Neutron stars are made out of cold ultra-dense matter. How this matter behaves is one of the biggest mysteries in modern nuclear physics. Researchers developed a new method for measuring the radius of neutron stars which helps them to understand what happens to the matter inside the star under extreme pressure. A new method for measuring neutron star size was developed in a study led by a high-energy astrophysics research group at the University of Turku, Finland. The method relies on modelling how thermonuclear explosions taking place in the uppermost layers of the star emit X-rays to us. By comparing the observed X-ray radiation from neutron stars to the state-of-the-art theoretical radiation models, researchers were able to put constraints on the size of the emitting source. This new analysis suggests that the neutron star radius should be about 12.4 kilometers. "Previous measurements have shown that the radius of a neutron star is circa 10-16 kilometres. We constrained it to be around 12 kilometres with about 400 meters accuracy, or maybe 1000 meters if one wants to be really sure. Therefore, the new measurement is a clear improvement compared to that before, says Doctoral Candidate Joonas Nattila from the University of Turku who developed the method.

The new measurements help researchers to study what kind of nuclear-physical conditions exist inside extremely dense neutron stars. Researchers are particularly interested in determining equation of state of the neutron matter, which shows how compressible the matter is at extremely high densities.

"The density of neutron star matter is circa 100 million tons per cubic centimetre. At the moment, neutron stars are the only objects appearing in nature, with which these types of extreme states of matter can be studied," says Juri Poutanen, the leader of the research group.

The new results also help to understand the recently discovered gravitational waves that originated from the collision of two neutron stars. That is why the LIGO/VIRGO consortium that discovered these waves was quick to compare their recent observations with the new constraints obtained by the Finnish researchers.

"The specific shape of the gravitational wave signal is highly dependent on the radii and the equation of state of the neutron stars. It is very exciting how these two completely different measurements tell the same story about the composition of neutron stars. The next natural step is to combine these two results. We have already been having active discussions with our colleagues on how to do this," says Nattila.

The Most Powerful Magnets in the Universe Are Collapsed Stars

When a large star dies, sometimes it becomes a neutron star, a tiny, 12 mile across ball that's made almost entirely out of neutrons. These dead stars are incredibly dense, and spin incredibly fast. Just one thimbleful of neutron star would weigh 100 million tons. Magnetars are a variation of neutron stars, and they somehow manage to be even scarier. Neutron stars already have extremely strong magnetic fields--about 2 trillion times more powerful than Earth's. Yet magnetars have magnetic fields 1,000 times stronger than that. Yeah, that's a pretty intense field. Magnetars are not just insanely powerful--they're also very, very dangerous. If you were a mere 1,000 kilometers from a magnetar, your entire body would dissolve as the magnetic field rearranged the sequence of atoms in your body. 

In addition to their terrifying magnetic powers, magnetars also have something called starquakes, which function similarly to earthquakes here on Earth--except with much more intense results. A crack in the crust of a magnetar is responsible for the brightest light we've ever observed from space. And if a magnetar was closer to us, like 10 light years away, and blasted us with the radiation from a starquake, it would destroy our ozone layer and probably kill all life on Earth.

But don't worry--thankfully, there aren't any magnetars near Earth. The closest one is about 9,000 light years away. Let's pray that it stays that way.

Three New Gas Giants May Provide Hint Into Major Astronomical Mystery

European astronomers with the Super Wide Angle Search for Planets (SuperWASP) consortium of planet hunters have detected three new gas giant alien worlds.The SuperWASP is an international effort to use the Roque de los Muchachos Observatory in Spain and the South African Astronomical Observatory to discover exoplanets. Both observatories are equipped with eight wide-angle cameras that monitor the sky for planetary transit events (when planets pass in front of their stars, allowing them to be imaged by human telescopes). The three planets were discovered orbiting three stars also discovered by the SuperWASP program: WASP-151, WASP-153 and WASP-156. "In this paper, we report the discovery of three transiting exoplanets by the SuperWASP survey and the SOPHIE spectrograph with mass and radius determined with a precision better than 15 percent," wrote the astronomers, led by a team out of the University of Porto in Portugal.

Two of the planets are "hot Saturns," large but low-density gas giants that are very close to their stars. The larger of the two, WASP-153b, has a radius 1.86 times that of Saturn and is 1.3 times as dense. The smaller hot Saturn, WASP-151b, is 1.36 times larger than Saturn and is 1.03 times as dense. Both of them have orbital periods of less than a week.

Meanwhile, the third planet is a "super-Neptune:" a planet appreciably bigger than Neptune (2.5 times more massive in this case) but smaller than Saturn, which is about five times more massive than Neptune. This third planet, WASP-156b, only needs 3.83 days to complete a revolution around its star.

This third find is the exciting one to astronomers, as shockingly few super-Neptunes have been discovered — a dearth named the so-called "Neptunian Desert." Many terrestrial planets (like Earth and Venus), gas giants (like Jupiter and Saturn), and super-Earths (like Uranus and Neptune) have been discovered. Meanwhile 156b is only the ninth-ever super-Neptune to be found of the thousand-plus exoplanets confirmed — and nobody is sure why.

"These three planets also lie close to (WASP-151b and WASP-153b) or below (WASP-156b) the upper boundary of the Neptunian desert. (…) While a detailed analysis of the origin of the Neptunian desert is beyond the scope of this paper, it is still interesting to look into the similarities and differences between WASP-156b and WASP-151b/WASP-153b since they might provide useful hints on the nature of this desert," the paper reads.