Ancient, Massive Asteroid Impact Could Explain Martian Geological Mysteries

Ancient, Massive Asteroid Impact Could Explain Martian Geological Mysteries:

The origin and nature of Mars are mysterious. The planet has geologically distinct hemispheres with smooth lowlands in the north and cratered, high-elevation terrain in the south. The red planet also has two small oddly-shaped oblong moons and a composition that sets it apart from that of the Earth.

New research by CU Boulder professor Stephen Mojzsis outlines a likely cause for these mysterious features of Mars: a colossal impact with a large asteroid early in the planet’s history. This asteroid—about the size of Ceres, one of the largest asteroids in the solar system—smashed into Mars, ripped off a chunk of the northern hemisphere and left behind a legacy of metallic elements in the planet’s interior. The crash also created a ring of rocky debris around Mars that may have later clumped together to form its moons, Phobos and Deimos.

The study appeared online in the journal Geophysical Research Letters, a publication of the American Geophysical Union, in June. 

“We showed in this paper—that from dynamics and from geochemistry—that we could explain these three unique features of Mars,” said Mojzsis, a professor in CU Boulder’s Department of Geological Sciences. “This solution is elegant, in the sense that it solves three interesting and outstanding problems about how Mars came to be.”

Astronomers have long wondered about these features. Over 30 years ago, scientists proposed a large asteroid impact to explain the disparate elevations of Mars’ northern and southern hemispheres; the theory became known as the “single impact hypothesis.” Other scientists have suggested that erosion, plate tectonics or ancient oceans could have sculpted the distinct landscapes. Support for the single impact hypothesis has grown in recent years, supported by computer simulations of giant impacts.

Mojzsis thought that by studying Mars’ metallic element inventory, he might be able to better understand its mysteries. He teamed up with Ramon Brasser, an astronomer at the Earth-Life Science Institute at the Tokyo Institute of Technology in Japan, to dig in.

The team studied samples from Martian meteorites and realized that an overabundance of rare metals—such as platinum, osmium and iridium—in the planet’s mantle required an explanation. Such elements are normally captured in the metallic cores of rocky worlds, and their existence hinted that Mars had been pelted by asteroids throughout its early history. By modeling how a large object such as an asteroid would have left behind such elements, Mojzsis and Brasser explored the likelihood that a colossal impact could account for this metal inventory.

The two scientists first estimated the amount of these elements from Martian meteorites, and deduced that the metals account for about 0.8 percent of Mars’ mass. Then, they used impact simulations with different-sized asteroids striking Mars to see which size asteroid accumulated the metals at the rate they expected in the early solar system.

Based on their analysis, Mars’ metals are best explained by a massive meteorite collision about 4.43 billion years ago, followed by a long history of smaller impacts. In their computer simulations, an impact by an asteroid at least 1,200 kilometers (745 miles) across was needed to deposit enough of the elements. An impact of this size also could have wildly changed the crust of Mars, creating its distinctive hemispheres.

In fact, Mojzsis said, the crust of the northern hemisphere appears to be somewhat younger than the ancient southern highlands, which would agree with their findings.

“The surprising part is how well it fit into our understanding of the dynamics of planet formation,” said Mojzsis, referring to the theoretical impact. “Such a large impact event elegantly fits in to what we understand from that formative time.”

Such an impact would also be expected to have generated a ring of material around Mars that later coalesced into Phobos and Deimos; this explains in part why those moons are made of a mix of native and non-Martian material. 

In the future, Mojzsis will use CU Boulder’s collection of Martian meteorites to further understand Mars’ mineralogy and what it can tell us about a possible asteroid impact. Such an impact should have initially created patchy clumps of asteroid material and native Martian rock. Over time, the two material reservoirs became mixed. By looking at meteorites of different ages, Mojzsis can see if there’s further evidence for this mixing pattern and, therefore, potentially provide further support for a primordial collision.

“Good theories make predictions,” said Mojzsis, referring to how the impact theory may predict how Mars’ makeup. By studying meteorites from Mars and linking them with planet-formation models, he hopes to better our understanding of how massive, ancient asteroids radically changed the red planet in its earliest days.

Credit: colorado.edu

Scientists Reveal New Connections Between Small Particles and the Vast Universe

Scientists Reveal New Connections Between Small Particles and the Vast Universe:

Our observable universe is the largest object that physicists study: It spans a diameter of almost 100 billion light years. The density correlations in our universe, for example, correlations between numbers of galaxies at different parts of the universe, indicate that our vast universe has originated from a stage of cosmic inflation.

On the other hand, elementary particles are the smallest object that physicists study. A particle physics Standard Model (SM) was established 50 years ago, describing all known particles and their interactions.

Are density distributions of the vast universe and the nature of smallest particles related? In a recent research, scientists from the Hong Kong University of Science and Technology (HKUST) and Harvard University revealed the connection between those two aspects, and argued that our universe could be used as a particle physics "collider" to study the high energy particle physics. Their findings mark the first step of cosmological collider phenomenology and pave the way for future discovery of new physics unknown yet to mankind.

The research was published in the journal Physical Review Letters on June 29, 2017 (doi:10.1103/PhysRevLett.118.261302) and the preprint is available online (https://arxiv.org/abs/1610.06597).

"Ongoing observations of cosmological microwave background and large scale structures have achieved impressive precision, from which valuable information about primordial density perturbations can be extracted, " said Yi Wang, a co-author of the paper and an assistant professor at HKUST's department of physics. "A careful study of this SM background would be the prerequisite for using the cosmological collider to explore any new physics, and any observational signal that deviates from this background would then be a sign of physics beyond the SM."

The team carried out a two-step task to work out the background of the SM model. The first step was to work out the SM spectrum during inflation, which turned out to be dramatically different from that obtained from the particle physics calculation in flat space. The second one was to figure out how the SM fields entered the cosmological density correlation functions.

"Just like the line pattern of the light you see when observing a mercury lamp through a spectrometer, the mass distribution of the fundamental particles in SM also presents a special pattern, or a 'mass spectrum', which can be viewed as the fingerprint of SM," explained Zhong-Zhi Xianyu, a co-author and physicist at Center for Mathematical Sciences and Applications in Harvard University, "However, this fingerprint is subject to change if we change the ambient conditions. Just like the light spectrum changes when applying strong magnetic field to the lamp, the spectrum of the SM particles turns out to be very different at the time of inflation from it is now due to the inflationary background." The team carefully examined all effects from inflation and showed how the mass spectrum of SM would look like for different inflation models.

"Through inflation, the spectrum of elementary particles is encoded in the statistics of the distribution of the contents of the universe, such as the galaxies and cosmic microwave background, that we observe today", explains Xingang Chen, a co-author and scientist in the Harvard-Smithsonian Center for Astrophysics. "This is the connection between the smallest and largest."

Many problems along this direction remain to be explored. "In our minimal setup, the Standard Model particles interact with the inflaton (the driving force of inflation) rather weakly. But if some new particles can mediate stronger interactions between these two sectors, we would expect to observe a stronger signal of new physics," said Wang. "The cosmological collider is an ideal arena for new physics beyond SM."

Credit: eurekalert.org

Hubble Sees Phobos Orbiting the Red Planet

Hubble Sees Phobos Orbiting the Red Planet:

The sharp eye of NASA's Hubble Space Telescope has captured the tiny moon Phobos during its orbital trek around Mars. Because the moon is so small, it appears star-like in the Hubble pictures. Over the course of 22 minutes, Hubble took 13 separate exposures, allowing astronomers to create a time-lapse video showing the diminutive moon's orbital path. The Hubble observations were intended to photograph Mars, and the moon's cameo appearance was a bonus.

A football-shaped object just 16.5 miles by 13.5 miles by 11 miles, Phobos is one of the smallest moons in the solar system. It is so tiny that it would fit comfortably inside the Washington, D.C. Beltway.

The little moon completes an orbit in just 7 hours and 39 minutes, which is faster than Mars rotates. Rising in the Martian west, it runs three laps around the Red Planet in the course of one Martian day, which is about 24 hours and 40 minutes. It is the only natural satellite in the solar system that circles its planet in a time shorter than the parent planet's day.

About two weeks after the Apollo 11 manned lunar landing on July 20, 1969, NASA's Mariner 7 flew by the Red Planet and took the first crude close-up snapshot of Phobos. On July 20, 1976 NASA's Viking 1 lander touched down on the Martian surface. A year later, its parent craft, the Viking 1 orbiter, took the first detailed photograph of Phobos, revealing a gaping crater from an impact that nearly shattered the moon.

​Phobos was discovered by Asaph Hall on August 17, 1877 at the U.S. Naval Observatory in Washington, D.C., six days after he found the smaller, outer moon, named Deimos. Hall was deliberately searching for Martian moons.

Both moons are named after the sons of Ares, the Greek god of war, who was known as Mars in Roman mythology. Phobos (panic or fear) and Deimos (terror or dread) accompanied their father into battle.

Close-up photos from Mars-orbiting spacecraft reveal that Phobos is apparently being torn apart by the gravitational pull of Mars. The moon is marred by long, shallow grooves that are probably caused by tidal interactions with its parent planet. Phobos draws nearer to Mars by about 6.5 feet every hundred years. Scientists predict that within 30 to 50 million years, it either will crash into the Red Planet or be torn to pieces and scattered as a ring around Mars.

Orbiting 3,700 miles above the Martian surface, Phobos is closer to its parent planet than any other moon in the solar system. Despite its proximity, observers on Mars would see Phobos at just one-third the width of the full moon as seen from Earth. Conversely, someone standing on Phobos would see Mars dominating the horizon, enveloping a quarter of the sky.

From the surface of Mars, Phobos can be seen eclipsing the sun. However, it is so tiny that it doesn't completely cover our host star. Transits of Phobos across the sun have been photographed by several Mars-faring spacecraft.

The origin of Phobos and Deimos is still being debated. Scientists concluded that the two moons were made of the same material as asteroids. This composition and their irregular shapes led some astrophysicists to theorize that the Martian moons came from the asteroid belt.

However, because of their stable, nearly circular orbits, other scientists doubt that the moons were born as asteroids. Such orbits are rare for captured objects, which tend to move erratically. An atmosphere could have slowed down Phobos and Deimos and settled them into their current orbits, but the Martian atmosphere is too thin to have circularized the orbits. Also, the moons are not as dense as members of the asteroid belt.

Phobos may be a pile of rubble that is held together by a thin crust. It may have formed as dust and rocks encircling Mars were drawn together by gravity. Or, it may have experienced a more violent birth, where a large body smashing into Mars flung pieces skyward, and those pieces were brought together by gravity. Perhaps an existing moon was destroyed, reduced to the rubble that would become Phobos.

Hubble took the images of Phobos orbiting the Red Planet on May 12, 2016, when Mars was 50 million miles from Earth. This was just a few days before the planet passed closer to Earth in its orbit than it had in the past 11 years.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

Credit: NASA

Asteroid 2017 BS5 to Pass by Earth on Sunday

Asteroid 2017 BS5 to Pass by Earth on Sunday:

An asteroid discovered in January is about to give Earth a close shave on Sunday, July 23. The object, designated 2017 BS5, will pass by our planet at 19:17 UTC at a safe distance of approximately 3.1 lunar distances (LD), or 1.19 million kilometers.

2017 BS5 was first observed on January 25, 2017 using the Asteroid Terrestrial-Impact Last Alert System (ATLAS) at Haleakala Observatory, Hawaii. It is an astronomical survey system for detection of dangerous asteroids a few weeks to days before their close approaches to Earth.

According to astronomers, 2017 BS5 is an Amor-type asteroid with an absolute magnitude of 24.1 and an estimated diameter between 28 and 90 meters. The object has a semimajor axis of about 1.0 AU and it takes it one year to fully orbit the sun. On Sunday, it will fly by our planet with a relative velocity of 5.8 km/s.

In the coming years 2017 BS5 will make close approaches to Earth twice a year. The next fly-by of this asteroid is expected to take place on January 17, 2018 when it will pass by our planet at a distance of approximately 41 LD.

Currently, there are 1,803 potentially hazardous asteroids (PHAs) detected to date. PHAs are space rocks larger than approximately 100 meters that can come closer to Earth than 19.5 LD. However, none of the known PHAs is on a collision course with our planet.

Ground-Breaking Ground-Based Images of Planets Obtained by Pic-Net Pro-Am Team

Ground-Breaking Ground-Based Images of Planets Obtained by Pic-Net Pro-Am Team:

The first observing run of a collaboration between amateur and professional astronomers to monitor our planetary neighbors has resulted in some of the best planetary images ever taken from the ground. The ‘Pic-Net’ project aims to use the one-meter diameter planetary telescope at the Pic du Midi Observatory in the French Pyrenees to monitor the meteorology of planets in our Solar System, measure global winds in their atmospheres, monitor impact of minor planet bodies producing giant fireballs in planetary atmospheres, and provide observational support for various space missions.

Last month, a small team of amateur astronomers carried out a pilot observing run during a workshop funded by the Europlanet 2020 Research Infrastructure (RI). Superb-quality images of Jupiter, Saturn, Venus and Jupiter’s moon Ganymede were obtained during four nights of observations, as well as images of Uranus and Neptune.

“The key to the success of this project is our highly-experienced team of observers, the optical quality of the telescope, the highly stable atmosphere at the Pic du Midi observatory and cutting-edge instrumentation,” said Francois Colas, astronomer at the Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE) and telescope and instrumentation lead of the Pic-Net project. “We believe that these are some of the best planetary observations from the ground to date.”

Repeated observations with ground-based telescopes provide a long-term, global view of planets that can put the detailed, close-up data collected by orbiting space missions into context. Amateur astronomers with relatively small telescopes can make extremely valuable scientific contributions by observing at dates where no equivalent data is available. Several observing runs like those from the Pic-Net pilot are needed over a year to understand the changes in the atmospheres of planets.

“Images obtained through Pic-Net can provide important, ongoing support for space missions,” said Marc Delcroix, an amateur astronomer who has piloted the use of the one-meter diameter telescope and is the organizer of the Europlanet workshop. “For instance, the high quality of Pic-Net observations of Saturn, which show clearly the hexagon feature surrounding the north polar vortex, atmospheric bands and cloud features, will also provide an avenue for continued study of Saturn and build on the legacy of the Cassini mission, which ends in September.”

Over the last 15 years, amateur astronomers have proven their skills, experience and potential in planetary imaging using new fast cameras that ‘freeze’ optical distortions introduced by the atmosphere on high-resolution telescopic observations. Professional astronomers collaborate closely with amateurs in many areas of planetary sciences, including the study of the atmospheres of planets like Venus, Jupiter or Saturn.

The ultimate goal of the Pic-Net project is to provide experienced observers with more access to the Pic-Midi facility in order to extract the full potential of the telescope and the observing site over time. Regular visits with an enlarged team of observers are envisioned as part of the Pic-Net project.

“The Pic-Net program provides invaluable support for the Juno mission and complements other Earth-based observations from professional astronomers,” noted Glenn Orton of Jet Propulsion Laboratory, California Institute of Technology, who is the Juno science team member in charge of coordinating Earth-based observations to extend and enhance the science return from Juno’s investigation of Jupiter and its magnetosphere.

Orton added, “These observations not only provide details on planetary cloud morphology that are close to what we might expect from the Hubble Space Telescope, but also such a program of regular observing allows us to understand the evolution of intermediate- to small-sized features on a variety of time scales, helping Juno scientists to understand the history of features for which the spacecraft only gets one or two ‘snapshots’ on each close approach.”

Javier Peralta, team member of JAXA’s Akatsuki mission commented, “In the case of Venus, the amateur observations have experienced incredible steps forward in the last years. Images in ultraviolet and near-infrared wavelengths permit the study of winds at two altitudes of the dayside clouds, even when Venus is close to being at its furthest point from Earth, while smart combinations of infrared filters for nightside observations now allow us to clearly resolve many surface elevations. These are much needed in support of the Akatsuki mission.”

Credit: europlanet-eu.org

Spiral Arms Allow School Children to Weigh Black Holes

Spiral Arms Allow School Children to Weigh Black Holes:

Astronomers from Swinburne University of Technology, Australia, and the University of Minnesota Duluth, USA, have provided a way for armchair astronomers, and even primary school children, to merely look at a spiral galaxy and estimate the mass of its hidden, central black hole. The research was supported by the Australian Research Council and has been published in the journal Monthly Notices of the Royal Astronomical Society​.

Given that black holes emit no discernible light, they have traditionally been studied via highly technical observations of the stars and gas orbiting around them, which in turn provide a measurement of how massive they must be.

Now, new research based on these pre-existing measurements has shown that a black hole’s mass can be accurately estimated by simply looking at the spiral arms of its host galaxy.

Nearly a century ago, Sir James Jeans and Edwin Hubble noted how spiral galaxies with large central bulges possess tightly wound spiral arms, while spiral galaxies with small bulges display wide open spiral arms. Since then, hundreds of thousands, if not millions, of spiral galaxies have been classified as type Sa, Sb, Sc, Sd, depending on their spiral arms.

Prof Marc Seigar, Associate Dean of the Swenson College of Science and Engineering at the University of Minnesota Duluth, and co-author of the study, discovered a relationship between central black hole mass and the tightness of a galaxy’s spiral arms nearly a decade ago.

Dr Benjamin Davis and Prof Alister Graham, from Swinburne’s Centre for Astrophysics and Supercomputing, led the new research revising this connection between black hole mass and spiral arm geometry.

After carefully analyzing a larger sample of galaxies, imaged by an array of space telescopes, the researchers observed an unexpectedly strong relationship, and one which predicts lower mass black holes in galaxies with open spiral arms (types Sc and Sd).

“The strength of the correlation is competitive with, if not better than, all our other methods used to predict black hole masses,” says Dr Davis. “Anyone can now look at an image of a spiral galaxy and immediately gauge how massive its black hole should be.”

Given that it is the discs of galaxies that host the spiral pattern, the study highlights the poorly-known connection between galaxy discs and black holes. Moreover, the procedure allows for the prediction of black hole masses in pure disc galaxies with no stellar bulge. “This implies that black holes and the discs of their host galaxies must co-evolve,” says Dr Davis.

"It's now as easy as 'a,b,c' to unlock this mystery of our Universe and reveal the black hole masses in spiral galaxies,” says Prof Graham.

“Importantly, the relation will also help searches for the suspected, but currently missing, population of intermediate-mass black holes with masses between 100 and 100,000 times the mass of our Sun. Difficult to pin down, they have masses greater than that of any single star, but are smaller than the supermassive black holes which grow to billions of times the mass of our Sun in giant galaxies,” Prof Graham says.

Working within the Australian Research Council’s OzGrav Centre for Excellence, the astronomers intend to hunt down these elusive black holes, and investigate implications for the production of gravitational waves: those ripples in the fabric of Einstein’s space-time that were first announced by the LIGO and Virgo collaborations in 2016.

Credit: ras.org.uk

Scientists Get Best Measure of Star-forming Material in Galaxy Clusters in Early Universe

Scientists Get Best Measure of Star-forming Material in Galaxy Clusters in Early Universe:

The international Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) collaboration based at the University of California, Riverside has combined observations from several of the world’s most powerful telescopes to carry out one of the largest studies yet of molecular gas – the raw material which fuels star formation throughout the universe – in three of the most distant clusters of galaxies ever found, detected as they appeared when the universe was only four billion years old.

Results were recently published in The Astrophysical Journal Letters. Allison Noble, a postdoctoral researcher at the Massachusetts Institute of Technology, led this newest research from the SpARCS collaboration.

Clusters are rare regions of the universe consisting of tight groups of hundreds of galaxies containing trillions of stars, as well as hot gas and mysterious dark matter. First, the research team used spectroscopic observations from the W. M. Keck Observatory on Mauna Kea, Hawai’i, and the Very Large Telescope in Chile that confirmed 11 galaxies were star-forming members of the three massive clusters. Next, the researchers took images through multiple filters from NASA’s Hubble Space Telescope, which revealed a surprising diversity in the galaxies’ appearance, with some galaxies having already formed large disks with spiral arms.

One of the telescopes the SpARCS scientists used is the extremely sensitive Atacama Large Millimeter Array (ALMA) telescope capable of directly detecting radio waves emitted from the molecular gas found in galaxies in the early universe. ALMA observations allowed the scientists to determine the amount of molecular gas in each galaxy, and provided the best measurement yet of how much fuel was available to form stars.

The researchers compared the properties of galaxies in these clusters with the properties of “field galaxies” (galaxies found in more typical environments with fewer close neighbors). To their surprise, they discovered that cluster galaxies had higher amounts of molecular gas relative to the amount of stars in the galaxy, compared to field galaxies. The finding puzzled the team because it has long been known that when a galaxy falls into a cluster, interactions with other cluster galaxies and hot gas accelerate the shut off of its star formation relative to that of a similar field galaxy (the process is known as environmental quenching).

“This is definitely an intriguing result,” said Gillian Wilson, a professor of physics and astronomy at UC Riverside and the leader of the SpARCS collaboration. “If cluster galaxies have more fuel available to them, you might expect them to be forming more stars than field galaxies, and yet they are not.”

Noble, a SpARCS collaborator and the study’s leader, suggests several possible explanations: It is possible that something about being in the hot, harsh cluster environment surrounded by many neighboring galaxies perturbs the molecular gas in cluster galaxies such that a smaller fraction of that gas actively forms stars. Alternatively, it is possible that an environmental process, such as increased merging activity in cluster galaxies, results in the observed differences between the cluster and field galaxy populations.

“While the current study does not answer the question of which physical process is primarily responsible for causing the higher amounts of molecular gas, it provides the most accurate measurement yet of how much molecular gas exists in galaxies in clusters in the early universe,” Wilson said.

The SpARCS team has developed new techniques using infrared observations from NASA’s Spitzer Space Telescope to identify hundreds of previously undiscovered clusters of galaxies in the early universe. In the future, they plan to study a larger sample of clusters. The team has recently been awarded additional time on ALMA, the W. M. Keck Observatory, and the Hubble Space Telescope to continue investigating how the neighborhood in which a galaxy lives determines for how long it can form stars.

Credit: ucr.edu

Astronomer Develops New Ways to See the Formation of Stars and Discovers Never-Before Seen Areas in Our Milky Way Galaxy

Astronomer Develops New Ways to See the Formation of Stars and Discovers Never-Before Seen Areas in Our Milky Way Galaxy:

A research team led by Adler Planetarium astronomer Dr. Grace Wolf-Chase has discovered new evidence of stars forming in our Milky Way Galaxy. By using a telescope equipped to detect infrared light invisible to our eyes, this exciting new science is revealing how stars, including our very own Sun, grow up within clusters and groups. The Astrophysical Journal has published a paper on the subject titled, “MHOs toward HMOs: A Search for Molecular Hydrogen Emission-Line Objects toward High-Mass Outflows.”

The team found huge gas clouds moving outward from areas where “baby” stars are forming, using a new way of disentangling these outflows from other processes in densely-populated stellar nurseries. These stellar nurseries can produce dozens or even hundreds of stars with different sizes and masses.

“The Sun, though isolated from other stars today, is thought to have formed in a cluster with many other stars, so the environments we’re studying can tell us a lot about the origin of our own Solar System,” said Wolf-Chase.

Stars form when cold, rotating clouds of gas and dust in space are pulled together by gravity into flattened “disks” that spin faster as they shrink, similar to what happens when twirling figure skaters pull their outstretched arms in toward their bodies. In order for a star to form at the center of a spinning disk, the rotation of the disk must slow down. This happens through powerful outflows of gas that are channeled into tight streams, known as “jets.” Jets can span more than 10 trillion miles, even though the disks that launch them are “mere” billions of miles across (comparable to the size of our Solar System.) Since planets can form in the disks, the presence of a jet can be a good indicator of a nascent planetary system, even when the disk isn’t observed directly. Stars more than eight times as massive as the Sun bathe their surroundings in intense ultraviolet radiation that destroys their natal clouds quickly, so it’s not clear if these massive stars develop disks and jets similar to stars like the Sun.

The researchers used an instrument called NICFPS (which stands for Near-Infrared Camera and Fabry-Perot Spectrometer) on the Astrophysical Research Consortium (ARC) 3.5-meter telescope at the Apache Point Observatory (APO) in Sunspot, New Mexico. NICFPS peered into 26 dusty clouds thought to be forming clusters containing massive stars. Using a combination of infrared filters that allowed them to distinguish jets from infant stars from other types of light produced by the radiation in these massive stellar nurseries, they identified 36 jets across 22 of the regions. These results provide compelling evidence that, like their lower-mass siblings, massive stars also launch powerful jets. The jet shuts off shortly after radiation from the massive star begins to disrupt its environment.

Grace Wolf-Chase, an Astronomer at the Adler Planetarium, is first author of this paper. Coauthors are former Postdoctoral Scholar at the Adler Planetarium, Kim Arvidsson, who is currently Assistant Professor of Physics in the Trull School of Sciences and Mathematics at Schreiner University in Kerrville, Texas; and Michael Smutko, Professor of Instruction in the Department of Physics and Astronomy at Northwestern University and former Astronomer at the Adler Planetarium. Astronomical research at the Adler Planetarium is funded in part through a generous grant from the Brinson Foundation. This project also received a Research Seed Grant through NASA’s Illinois Space Grant Consortium.

Credit: adlerplanetarium.org

Holographic Imaging Could Be Used to Detect Signs of Life in Space

Holographic Imaging Could Be Used to Detect Signs of Life in Space:

We may be capable of finding microbes in space—but if we did, could we tell what they were, and that they were alive? This month the journal Astrobiology is publishing a special issue dedicated to the search for signs of life on Saturn's icy moon Enceladus. Included is a paper from Caltech's Jay Nadeau and colleagues offering evidence that a technique called digital holographic microscopy, which uses lasers to record 3-D images, may be our best bet for spotting extraterrestrial microbes.

No probe since NASA's Viking program in the late 1970s has explicitly searched for extraterrestrial life—that is, for actual living organisms. Rather, the focus has been on finding water. Enceladus has a lot of water—an ocean's worth, hidden beneath an icy shell that coats the entire surface. But even if life does exist there in some microbial fashion, the difficulty for scientists on Earth is identifying those microbes from 790 million miles away.

"It's harder to distinguish between a microbe and a speck of dust than you'd think," says Nadeau, research professor of medical engineering and aerospace in the Division of Engineering and Applied Science. "You have to differentiate between Brownian motion, which is the random motion of matter, and the intentional, self-directed motion of a living organism."

Enceladus is the sixth-largest moon of Saturn, and is 100,000 times less massive than Earth. As such, Enceladus has an escape velocity—the minimum speed needed for an object on the moon to escape its surface—of just 239 meters per second. That is a fraction of Earth's, which is a little over 11,000 meters per second.

Enceladus's minuscule escape velocity allows for an unusual phenomenon: enormous geysers, venting water vapor through cracks in the moon's icy shell, regularly jet out into space. When the Saturn probe Cassini flew by Enceladus in 2005, it spotted water vapor plumes in the south polar region blasting icy particles at nearly 2,000 kilometers per hour to an altitude of nearly 500 kilometers above the surface. Scientists calculated that as much as 250 kilograms of water vapor were released every second in each plume. Since those first observations, more than a hundred geysers have been spotted. This water is thought to replenish Saturn's diaphanous E ring, which would otherwise dissipate quickly, and was the subject of a recent announcement by NASA describing Enceladus as an "ocean world" that is the closest NASA has come to finding a place with the necessary ingredients for habitability.

Water blasting out into space offers a rare opportunity, says Nadeau. While landing on a foreign body is difficult and costly, a cheaper and easier option might be to send a probe to Enceladus and pass it through the jets, where it would collect water samples that could possibly contain microbes.

Assuming a probe were to do so, it would open up a few questions for engineers like Nadeau, who studies microbes in extreme environments. Could microbes survive a journey in one of those jets? If so, how could a probe collect samples without destroying those microbes? And if samples are collected, how could they be identified as living cells?

The problem with searching for microbes in a sample of water is that they can be difficult to identify. "The hardest thing about bacteria is that they just don't have a lot of cellular features," Nadeau says. Bacteria are usually blob-shaped and always tiny—smaller in diameter than a strand of hair. "Sometimes telling the difference between them and sand grains is very difficult," Nadeau says.

Some strategies for demonstrating that a microscopic speck is actually a living microbe involve searching for patterns in its structure or studying its specific chemical composition. While these methods are useful, they should be used in conjunction with direct observations of potential microbes, Nadeau says.

"Looking at patterns and chemistry is useful, but I think we need to take a step back and look for more general characteristics of living things, like the presence of motion. That is, if you see an E. coli, you know that it is alive—and not, say, a grain of sand—because of the way it is moving," she says. In earlier work, Nadeau suggested that the movement exhibited by many living organisms could potentially be used as a robust, chemistry-independent biosignature for extraterrestrial life. The motion of living organisms can also be triggered or enhanced by "feeding" the microbes electrons and watching them grow more active.

To study the motion of potential microbes from Enceladus's plumes, Nadeau proposes using an instrument called a digital holographic microscope that has been modified specifically for astrobiology.

In digital holographic microscopy, an object is illuminated with a laser and the light that bounces off the object and back to a detector is measured. This scattered light contains information about the amplitude (the intensity) of the scattered light, and about its phase (a separate property that can be used to tell how far the light traveled after it scattered). With the two types of information, a computer can reconstruct a 3-D image of the object—one that can show motion through all three dimensions.

"Digital holographic microscopy allows you to see and track even the tiniest of motions," Nadeau says. Furthermore, by tagging potential microbes with fluorescent dyes that bind to broad classes of molecules that are likely to be indicators of life—proteins, sugars, lipids, and nucleic acids—"you can tell what the microbes are made of," she says.

To study the technology's potential utility for analyzing extraterrestrial samples, Nadeau and her colleagues obtained samples of frigid water from the Arctic, which is sparsely populated with bacteria; those that are present are rendered sluggish by the cold temperatures.

With holographic microscopy, Nadeau was able to identify organisms with population densities of just 1,000 cells per milliliter of volume, similar to what exists in some of the most extreme environments on Earth, such as subglacial lakes. For comparison, the open ocean contains about 10,000 cells per milliliter and a typical pond might have 1–10 million cells per milliliter. That low threshold for detection, coupled with the system's ability to test a lot of samples quickly (at a rate of about one milliliter per hour) and its few moving parts, makes it ideal for astrobiology, Nadeau says. 

Next, the team will attempt to replicate their results using samples from other microbe-poor regions on Earth, such as Antarctica.

Nadeau collaborated with Caltech graduate student Manuel Bedrossian and Chris Lindensmith of JPL.

Credit: caltech.edu

Flashes of Light on the Dark Matter

Flashes of Light on the Dark Matter:

A web that passes through infinite intergalactic spaces, a dense cosmic forest illuminated by very distant lights and a huge enigma to solve. These are the picturesque ingredients of a scientific research - carried out by an international team composed of researchers from the International School for Adavnced Studies (SISSA) and the Abdus Salam International Center for Theoretical Physics (ICTP) in Trieste, the Institute of Astronomy of Cambridge and the University of Washington - that adds an important element for understanding one of the fundamental components of our Universe: the dark matter.

In order to study its properties, scientists analyzed the interaction of the "cosmic web" - a network of filaments made up of gas and dark matter present in the whole Universe - with the light coming from very distant quasars and galaxies. Photons interacting with the hydrogen of the cosmic filaments create many absorption lines defined "Lyman-alpha forest". This microscopic interaction succeeds in revealing several important properties of the dark matter at cosmological distances. The results further support the theory of Cold Dark Matter, which is composed of particles that move very slowly. Moreover, for the first time, they highlight the incompatibility with another model, i.e. the Fuzzy Dark Matter, for which dark matter particles have larger velocities. The research was carried out through simulations performed on international parallel supercomputers and has recently been published in Physical Review Letters.

Although constituting an important part of our cosmos, the dark matter is not directly observable, it does not emit electromagnetic radiation and it is visible only through gravitational effects. Besides, its nature remains a deep mystery. The theories that try to explore this aspect are various. In this research, scientists investigated two of them: the so-called Cold Dark Matter, considered a paradigm of modern cosmology, and an alternative model called Fuzzy Dark Matter (FDM), in which the dark matter is deemed composed of ultralight bosons provided with a non-negligible pressure at small scales. To carry out their investigations, scientists examined the cosmic web by analyzing the so-called Lyman-alpha forest. The Lyman-alpha forest consists of a series of absorption lines produced by the light coming from very distant and extremely luminous sources, that passes through the intergalactic space along its way toward the earth's telescopes. The atomic interaction of photons with the hydrogen present in the cosmic filaments is used to study the properties of the cosmos and of the dark matter at enormous distances.

Through simulations carried out with supercomputers, researchers reproduced the interaction of the light with the cosmic web. Thus they were able to infer some of the characteristics of the particles that compose the dark matter. More in particular, evidence showed for the first time that the mass of the particles, which allegedly compose the dark matter according to the FDM model, is not consistent with the Lyman-alpha Forest observed by the Keck telescope (Hawaii, US) and the Very Large Telescope (European Southern Observatory, Chile). Basically, the study seems not to confirm the theory of the Fuzzy Dark Matter. The data, instead, support the scenario envisaged by the model of the Cold Dark Matter.

The results obtained - scientists say - are important as they allow to build new theoretical models for describing the dark matter and new hypotheses on the characteristics of the cosmos. Moreover, these results can provide useful indications for the realization of experiments in laboratories and can guide observational efforts aimed at making progress on this fascinating scientific theme.

Credit: sissa.it

Hunting Molecules with the MWA

Hunting Molecules with the MWA:

Astronomers have used an Australian radio telescope to observe molecular signatures from stars, gas and dust in our galaxy, which could lead to the detection of complex molecules that are precursors to life. Using the Murchison Widefield Array (MWA), a radio telescope located in the Murchison region of Western Australia, the team successfully detected two molecules called the mercapto radical (SH) and nitric oxide (NO).

“The molecular transitions we saw are from slow variable stars—stars at the end of their lives that are becoming unstable,” said Chenoa Tremblay from the International Centre for Radio Astronomy Research (ICRAR) and Curtin University.

“We use molecules to probe the Milky Way, to better understand the chemical and physical environments of stars, gas and dust,” she said.

“One of the unique aspects of this survey is that until now, no one has ever reported detections of molecules within the 70-300MHz frequency range of the MWA and this is the widest field-of-view molecular survey of the Milky Way ever published.”

Since the 1980s, frequencies greater than 80GHz have been used for this type of work due to the freedom from radio frequency interference emitted by our mobile phones, televisions and orbiting satellites. But the extreme “radio quietness” of the Murchison Radio-astronomy Observatory, where the telescope is located, allows astronomers to study molecular signatures from stars and star-forming regions at lower frequencies.

“Before this study, the mercapto radical had only been seen twice before at infrared wavelengths, in a different part of the electromagnetic spectrum,” said Dr Maria Cunningham from the University of New South Wales.

“This shows that molecules are emitting photons detectable around 100MHz and we can detect these molecular signatures using the MWA—it’s very exciting for us,” she said.

Following on from the pilot study, a survey of the Orion region is now in progress, again using the MWA, in the frequency range of 99-270MHz. The Orion nebula is a chemical-rich environment and one of the closest star-forming regions to Earth. The aim is to detect more chemical tracers in stars, compare these regions to the observations from the Galactic Centre pilot region and to better understand the emission mechanisms of these molecules.

“This new technique paves the way for deeper surveys that can probe the Milky Way and other galaxies in search of molecular precursors to life,” said Tremblay.

“We might even discover signatures from long chain amino acids in the cold gas environments we’re observing—which is where they are likely to be most stable.”

‘A First Look for Molecules between 103 and 133MHz using the Murchison Widefi eld Array’, was published in the Monthly Notices of the Royal Astronomical Society on July 21, 2017.

Credit: icrar.org

Superluminous Supernova Marks the Death of a Star at Cosmic High Noon

Superluminous Supernova Marks the Death of a Star at Cosmic High Noon:

The death of a massive star in a distant galaxy 10 billion years ago created a rare superluminous supernova that astronomers say is one of the most distant ever discovered. The brilliant explosion, more than three times as bright as the 100 billion stars of our Milky Way galaxy combined, occurred about 3.5 billion years after the big bang at a period known as "cosmic high noon," when the rate of star formation in the universe reached its peak.

Superluminous supernovae are 10 to 100 times brighter than a typical supernova resulting from the collapse of a massive star. But astronomers still don't know exactly what kinds of stars give rise to their extreme luminosity or what physical processes are involved.

The supernova known as DES15E2mlf is unusual even among the small number of superluminous supernovae astronomers have detected so far. It was initially detected in November 2015 by the Dark Energy Survey (DES) collaboration using the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile. Follow-up observations to measure the distance and obtain detailed spectra of the supernova were conducted with the Gemini Multi-Object Spectrograph on the 8-meter Gemini South telescope.

The investigation was led by UC Santa Cruz astronomers Yen-Chen Pan and Ryan Foley as part of an international team of DES collaborators. The researchers reported their findings in a paper published July 21 in the Monthly Notices of the Royal Astronomical Society.

The new observations may provide clues to the nature of stars and galaxies during peak star formation. Supernovae are important in the evolution of galaxies because their explosions enrich the interstellar gas from which new stars form with elements heavier than helium (which astronomers call "metals").

"It's important simply to know that very massive stars were exploding at that time," said Foley, an assistant professor of astronomy and astrophysics at UC Santa Cruz. "What we really want to know is the relative rate of superluminous supernovae to normal supernovae, but we can't yet make that comparison because normal supernovae are too faint to see at that distance. So we don't know if this atypical supernova is telling us something special about that time 10 billion years ago."

Previous observations of superluminous supernovae found they typically reside in low-mass or dwarf galaxies, which tend to be less enriched in metals than more massive galaxies. The host galaxy of DES15E2mlf, however, is a fairly massive, normal-looking galaxy.

"The current idea is that a low-metal environment is important in creating superluminous supernovae, and that's why they tend to occur in low mass galaxies, but DES15E2mlf is in a relatively massive galaxy compared to the typical host galaxy for superluminous supernovae," said Pan, a postdoctoral researcher at UC Santa Cruz and first author of the paper.

Foley explained that stars with fewer heavy elements retain a larger fraction of their mass when they die, which may cause a bigger explosion when the star exhausts its fuel supply and collapses.

"We know metallicity affects the life of a star and how it dies, so finding this superluminous supernova in a higher-mass galaxy goes counter to current thinking," Foley said. "But we are looking so far back in time, this galaxy would have had less time to create metals, so it may be that at these earlier times in the universe's history, even high-mass galaxies had low enough metal content to create these extraordinary stellar explosions. At some point, the Milky Way also had these conditions and might have also produced a lot of these explosions."

"Although many puzzles remain, the ability to observe these unusual supernovae at such great distances provides valuable information about the most massive stars and about an important period in the evolution of galaxies," said Mat Smith, a postdoctoral researcher at University of Southampton. The Dark Energy Survey has discovered a number of superluminous supernovae and continues to see more distant cosmic explosions revealing how stars exploded during the strongest period of star formation.

In addition to Pan, Foley, and Smith, the coauthors of the paper include Lluís Galbany of the University of Pittsburgh, and other members of the DES collaboration from more than 40 institutions. This research was funded the National Science Foundation, The Alfred P. Sloan Foundation, and the David and Lucile Packard Foundation.

Credit: ucsc.edu

Scientists Spy New Evidence of Water in the Moon’s Interior

Scientists Spy New Evidence of Water in the Moon’s Interior:

A new study of satellite data finds that numerous volcanic deposits distributed across the surface of the Moon contain unusually high amounts of trapped water compared with surrounding terrains. The finding of water in these ancient deposits, which are believed to consist of glass beads formed by the explosive eruption of magma coming from the deep lunar interior, bolsters the idea that the lunar mantle is surprisingly water-rich.

Scientists had assumed for years that the interior of the Moon had been largely depleted of water and other volatile compounds. That began to change in 2008, when a research team including Brown University geologist Alberto Saal detected trace amounts of water in some of the volcanic glass beads brought back to Earth from the Apollo 15 and 17 missions to the Moon. In 2011, further study of tiny crystalline formations within those beads revealed that they actually contain similar amounts of water as some basalts on Earth. That suggests that the Moon’s mantle — parts of it, at least — contain as much water as Earth’s.

“The key question is whether those Apollo samples represent the bulk conditions of the lunar interior or instead represent unusual or perhaps anomalous water-rich regions within an otherwise ‘dry’ mantle,” said Ralph Milliken, lead author of the new research and an associate professor in Brown’s Department of Earth, Environmental and Planetary Sciences. “By looking at the orbital data, we can examine the large pyroclastic deposits on the Moon that were never sampled by the Apollo or Luna missions. The fact that nearly all of them exhibit signatures of water suggests that the Apollo samples are not anomalous, so it may be that the bulk interior of the Moon is wet.”

The research, which Milliken co-authored with Shuai Li, a postdoctoral researcher at the University of Hawaii and a recent Brown Ph.D. graduate, is published in Nature Geoscience. The work was part of Li's Ph.D. thesis.

Detecting the water content of lunar volcanic deposits using orbital instruments is no easy task. Scientists use orbital spectrometers to measure the light that bounces off a planetary surface. By looking at which wavelengths of light are absorbed or reflected by the surface, scientists can get an idea of which minerals and other compounds are present.

The problem is that the lunar surface heats up over the course of a day, especially at the latitudes where these pyroclastic deposits are located. That means that in addition to the light reflected from the surface, the spectrometer also ends up measuring heat.

“That thermally emitted radiation happens at the same wavelengths that we need to use to look for water,” Milliken said. “So in order to say with any confidence that water is present, we first need to account for and remove the thermally emitted component.”

To do that, Li and Milliken used laboratory-based measurements of samples returned from the Apollo missions, combined with a detailed temperature profile of the areas of interest on the Moon’s surface. Using the new thermal correction, the researchers looked at data from the Moon Mineralogy Mapper, an imaging spectrometer that flew aboard India’s Chandrayaan-1 lunar orbiter.

The researchers found evidence of water in nearly all of the large pyroclastic deposits that had been previously mapped across the Moon’s surface, including deposits near the Apollo 15 and 17 landing sites where the water-bearing glass bead samples were collected.

“The distribution of these water-rich deposits is the key thing,” Milliken said. “They’re spread across the surface, which tells us that the water found in the Apollo samples isn’t a one-off. Lunar pyroclastics seem to be universally water-rich, which suggests the same may be true of the mantle.”

The idea that the interior of the Moon is water-rich raises interesting questions about the Moon’s formation. Scientists think the Moon formed from debris left behind after an object about the size of Mars slammed into the Earth very early in solar system history. One of the reasons scientists had assumed the Moon’s interior should be dry is that it seems unlikely that any of the hydrogen needed to form water could have survived the heat of that impact.

“The growing evidence for water inside the Moon suggest that water did somehow survive, or that it was brought in shortly after the impact by asteroids or comets before the Moon had completely solidified,” Li said. “The exact origin of water in the lunar interior is still a big question.”

In addition to shedding light on the water story in the early solar system, the research could also have implications for future lunar exploration. The volcanic beads don’t contain a lot of water — about .05 percent by weight, the researchers say — but the deposits are large, and the water could potentially be extracted.

“Other studies have suggested the presence of water ice in shadowed regions at the lunar poles, but the pyroclastic deposits are at locations that may be easier to access,” Li said. “Anything that helps save future lunar explorers from having to bring lots of water from home is a big step forward, and our results suggest a new alternative.”

Credit: brown.edu

Choose Your Star: First Gaia Data Release Catalogs More than Billion Celestial Objects

Choose Your Star: First Gaia Data Release Catalogs More than Billion Celestial Objects:

European Space Agency’s (ESA) Gaia satellite is on a crucial mission to create the most detailed ever 3D map of our Milky Way galaxy. Last year, the agency has published first data release provided by Gaia, which contains more than one billion stars with information about their brightness and precise position on the sky.

Finding an interesting star could be now as easy as browsing offers in order to find the best car for you on websites like Cars.com. Just like this site lists a plenitude of models from Acura to Volvo, the Gaia Data Release 1 (or DR1 for short) allows astronomers to investigate a variety of peculiar objects in the sky. While car buyers and enthusiasts can choose among a diversity of models, including Toyota Gaia, the scientific community has its own Gaia, flying in space and delivering essential astronomical data.

DR1 is a real treasure trove for astronomers studying stars in our galaxy. The catalog consists of astrometry and photometry data for over one billion sources brighter than magnitude 20.7 in the white-light photometric band G of the Gaia satellite. It is the largest all-sky survey of celestial objects to date.

ESA scientists underline that DR1 shows the density of stars measured by Gaia across the entire sky, and confirms that it has already collected superb data since the beginning of its operational life in July 2014. They note that the satellite charts the sky at precision that have never been achieved before.

In particular, DR1 contains about 1.14 billion stars with precise measurements of their position on the sky and brightness. The dataset allows astronomers to estimate distance and proper motion for over two billion stars in common with the earlier Hipparcos and Tycho-2 catalogs, based on data from ESA's Hipparcos mission. Moreover, DR1 also contains nearly 3,200 variable stars, including details about their brightness variations as well as positions and brightness of more than 2,000 quasi-stellar objects (quasars).

The promising results provided by DR1 leave the researchers hungry for more. Gaia mission scientists are convinced that subsequent data releases will revolutionize our understanding of how stars are distributed and move across the Milky Way.

“1,000 days after launch and thanks to the great work of everyone involved, we are thrilled to present this first dataset and are looking forward to the next release, which will unleash Gaia’s potential to explore our galaxy as we have never seen it before,” Fred Jansen, Gaia mission manager at ESA, said on September 14, 2016, when DR1 was published.

In general, DR1 confirms that Gaia is well on track of achieving it main goal – charting the positions, distances, and motions of one billion stars. It will be a 3D map of about one percent of the Milky Way’s stellar content – all with an unprecedented accuracy. Gaia’s second data release is currently planned for April 2018.