Month: March 2019

  • NASA's Mars Helicopter Completes Flight Tests

    PIA23151_hiresThis image of the flight model of NASA's Mars Helicopter was taken on Feb. 14, 2019, in a cleanroom at NASA's Jet Propulsion Laboratory in Pasadena, California. The aluminum base plate, side posts, and crossbeam around the helicopter protect the helicopter's landing legs and the attachment points that will hold it to the belly of the Mars 2020 rover. Image Credit: NASA/JPL-Caltech

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  • Asteroid (6478) Gault

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    About this image

    Hubble Witnesses Asteroid Coming Unglued

    This Hubble Space Telescope image reveals the gradual self-destruction of an asteroid, whose ejected dusty material has formed two long, thin, comet-like tails. The longer tail stretches more than 500,000 miles (800,000 kilometers) and is roughly 3,000 miles (4,800 kilometers) wide. The shorter tail is about a quarter as long. The streamers will eventually disperse into space.

    These unusual, transient features are evidence that the asteroid, known as (6478) Gault, is beginning to come apart by gently puffing off material in two separate episodes. Hubble's sharp view reveals that the tails are narrow streamers, suggesting that the dust was released in short bursts, lasting anywhere from a few hours to a few days.

    The first tail was spotted on Jan. 5, 2019; the second in mid-January. An analysis of both tails suggests the two dust releases occurred around Oct. 28 and Dec. 30, 2018.

    Astronomers think the tiny asteroid, only 2.5 miles wide, is disintegrating due to the long-term subtle effects of sunlight, which can slowly speed up its spin until it begins to shed material. In fact, the self-destruction may have been started more than 100 million years ago. Pressure from sunlight very slowly began spinning up the diminutive asteroid at an estimated rate of 1 second every 10,000 years.

    The asteroid is located 214 million miles from the Sun, between the orbits of Mars and Jupiter.

  • The Mars paradox: Why we still don't understand water on Mars

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    How did your water flow?NASA/JPL-Caltech/Univ. of Arizona

    By Chelsea Whyte

    SOMETHING doesn’t add up. Mars has ice caps, and there is evidence in the terrain that water flowed in rivers and lakes there billions of years ago. We have a decent understanding of how water behaves on Earth, and there’s no reason to think the laws of physics are different on Mars. And yet, we can’t figure out how water could have existed in liquid form on young Mars.

    Every time we try to replicate the conditions under which the liquid water could have existed, a new complication throws a wrench into our models. Last week, yet another paper tried to chip away at the mystery (PNAS, doi.org/bzjh). And like so many before it, instead of resolving the problem, it introduced another.

    This 40-year-old mystery is known as the Mars paradox. If and when we resolve it, we might need to throw away a lot of textbooks.

    Today, Mars’s cold, rocky terrain is dry and blanketed in dust. But observations of clay minerals and remnants of lake and river deposits are unequivocal: water flowed freely between 3.5 and 4 billion years ago

    The trouble starts when you look at the conditions on Mars at that time. Even today, Mars’s thin atmosphere and distance from the sun keep it, on average, at about -61°C, cold enough to hold existing water in permanent polar deposits. Billions of years ago, under a younger, less-heating sun, it was even colder.

    So given that the freezing point of water is the same on Earth as Mars, how was Mars ever warm enough for liquid water to flow? One plausible explanation is that greenhouse gases trapped heat in the way they do on Earth. These gases could have been produced by many sources, including volcanic eruptions. The gas with the best track record of trapping heat is carbon dioxide, because we know how much high concentrations heat Earth.

    “Every time we think we understand it, a new complication throws a wrench into the models”

    The problem is, no amount of CO2 can warm Mars enough for liquid water. Even with an atmosphere of pure CO2, the closest you get is -33°C.

    Not that the early Martian atmosphere was pure CO2. Last week’s paper examined sediments laid down 3.5 billion years ago, and found that the atmosphere then contained only scant amounts of carbon dioxide.

    Perhaps the maths could work if you added some methane or hydrogen? No. With that little CO2, it doesn’t matter how much hydrogen or methane or other gases you add into the equation. You need a thick atmosphere to begin with to shield these sensitive greenhouse gases from solar radiation.

    Last week’s paper offered another alternative: water salty enough to remain liquid even at water-freezing temperatures. Then the atmosphere wouldn’t need much CO2.

    But this too could fall short. Ultra-saline water can flow – on Earth at least – but a Mars that cold wouldn’t allow enough precipitation to account for the standing water etched into Mars’ sandstone and mudstone over millions of years.

    So is there some planetary mechanism we still don’t understand? A mixture of greenhouse gases we haven’t yet hit on? Perhaps the real trouble is our understanding of water itself. We already know it can bedevil a few laws of physics, like when colder water flows to the top of a glass. Whatever the answer, we’re running out of obvious solutions. We’re going to be in truly alien territory when the mystery is solved.

    This article appeared in print under the headline “Why water on Mars still doesn’t make sense”

  • Wild cosmic ducks

    Wild cosmic ducks

    This star-studded image shows us a portion of Messier 11, an open star cluster in the southern constellation of Scutum (The Shield). Messier 11 is also known as the Wild Duck Cluster, as its brightest stars form a “V” shape that somewhat resembles a flock of ducks in flight.

    Messier 11 is one of the richest and most compact open clusters currently known. By investigating the brightest, hottest main sequence stars in the cluster astronomers estimate that it formed roughly 220 million years ago. Open clusters tend to contain fewer and younger stars than their more compact globular cousins, and Messier 11 is no exception: at its centre lie many blue stars, the hottest and youngest of the cluster’s few thousand stellar residents.

    The lifespans of open clusters are also relatively short compared to those of globular ones; stars in open clusters are spread further apart and are thus not as strongly bound to each other by gravity, causing them to be more easily and quickly drawn away by stronger gravitational forces. As a result Messier 11 is likely to disperse in a few million years as its members are ejected one by one, pulled away by other celestial objects in the vicinity.

    Credit:

    ESA/Hubble & NASA, P. Dobbie et al.

  • We’ve found 4000 exoplanets but almost zero are right for life

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    Kepler-452b is the only known exoplanet with the right stuff for life – and even that’s a maybeNASA Ames/JPL-Caltech/T. Pyle

    By Leah Crane

    We have found more than 4000 planets orbiting distant stars, but it turns out that probably none of them have the right conditions for life to evolve, making Earth even more special than we thought.

    We normally consider a planet capable of hosting life if its surface is the right temperature for liquid water. This depends on how close it orbits its star – too far and any water will freeze, but too close and it will boil away. The area around each star where these water-friendly orbits lie is called the habitable zone.

    But just being technically habitable does not mean that a world has the right conditions for life to arise. One leading explanation for life’s emergence on Earth is that ultraviolet light from the sun played a role. The idea is that UV light hitting simple molecules gave them enough energy to react with one another, forming the more complicated compounds required to make a living organism.

    In 2018, researchers introduced a concept called the abiogenesis zone: the area around a star where a planet could get enough UV light to start this prebiotic chemistry, but not so much that the planet would be sterilised.

    Because one is based on temperature and the other on the strength of particular wavelengths of light, the habitable zone and the abiogenesis zone around any star do not always overlap.

    Marcos Jusino-Maldonado and Abel Méndez at the University of Puerto Rico at Arecibo applied the requirements for the abiogenesis zone to a list of known exoplanets in the habitable zone, of which we have found 49. Only eight worlds matched the criteria.

    “Even these eight are bad because they have a large radius, which means they might not be rocky,” says Jusino-Maldonado, who presented the work this week at the Lunar and Planetary Science Conference in Texas.

    Bigger planets tend to accrete gas as they grow, becoming gas giants like Neptune or Jupiter instead of rocky worlds like Earth or Mars. Previous work has suggested that planets larger than 1.7 times Earth’s radius are likely to be gassy.

    “If the planet is too big, it’d be hard to think how life as we know it could evolve,” says Ramses Ramirez at the Tokyo Institute of Technology. Of the eight planets inside both zones, only one has a radius less than 1.7 times Earth’s: a planet called Kepler-452b, which orbits a sun-like star 1400 light years away. Its radius is 1.63 Earth radii, so it is right on the edge.

    This means that out of more than 4000 exoplanets, we may have only found one where life could evolve – or perhaps even none, if Kepler-452b turns out to be a gas planet. The only two planets we know for sure to be rocky and in both the habitable and abiogenesis zones are Earth and Mars. As far as we can tell, Mars doesn’t have any life.

    This shows just how difficult it is likely to be for life to arise. “If our goal is to find life, we need to be finding a lot more exoplanets than we can see with the technology we have now,” says Ramirez.

    Plus, there is no guarantee that a planet where life could arise will actually have anything living on it. “It’s getting harder to find origins of life,” says Jusino-Maldonado. “It seems very unlikely.”

    More on these topics:

  • New, "pristine" fossils reveal secrets of Cambrian explosion

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    The Cambrian Period was a time of remarkable diversification of life when many of the animal groups that exist today first appear in the fossil record. (Ocean Portal / Smithsonian Institution)
    March 21, 2019

    The fossils from the Cambrian Period include dozens of new species and provide a window into life more than 500 million years ago

    smithsonian.com
    March 21, 2019

    The Cambrian was a time of vibrant, wonderful life. Fossil-packed sites like the Burgess Shale in Canada have revealed the unique nature of early animals around 508 million years ago. The strange creatures found in the rock are so delicately preserved that the ancient deposit seemed like a rarity, showing the unusual appendages and body shapes of the time.

    In the century since the Burgess Shale discovery, however, other fossil wonderlands of similar age have been uncovered elsewhere on the planet. The latest to be recognized was found in southern China: the Qingjiang Biota.

    In a paper published today in the journal Science, Paleontologist Dongjing Fu of Xi’an’s Northwest University and colleagues describes the Cambrian Period fossils. At 518 million years old, the collection is about 10 million years older than the Burgess Shale. The way the fossils formed, however, is similar to those in North America. Visible in high contrast as dark fossils on gray stone, the organisms of the Qingjiang Biota are preserved down to the finest details. The fossils include trilobites, jellyfish, shrimp-like arthropods and even tadpole-like animals from the earliest days of the vertebrate family.

    Dozens of these species have never been seen before. “What makes the Qingjaing special compared to other Cambrian sites with soft parts preserved, such as the Burgess Shale and Chengjiang Biota [in southern China], is the fact that there is over fifty percent entirely new taxa of animals and algae that are previously unknown to science,” says University of Lausanne paleontologist Allison Daley. Even better, she notes, is that the fossils are of “truly exceptional quality,” preserving the anatomy of the species without some of the natural distortions that sometimes result from the fossilization process.

    image: https://thumbs-prod.si-cdn.com/Ei0tukt3NcMomr5-docWArTOa14=/fit-in/1072x0/filters:focal(633x560:634x561)/https://public-media.si-cdn.com/filer/50/92/5092cdf9-d99a-43cd-9109-f84d03cd75f4/f2large_1.jpg

    Fossils

    (A) Leanchoilia sp., showing fine anatomical details, including those of the great appendages. (B) New megacherian preserved with internal soft tissues. (C) A possible kinorhynch scalidophoran, with segmented body armored by scalids. (D) Lobopodian. (E) Priapulid worm. (Dongjing Fu et al., Science 363:1338 (2019))

    “It shows how we have these little windows back to the past and how finding another site can change what we know,” says University of Bristol paleontologist Jakob Vinther.

    Some of the most beautiful specimens from the site are of soft-bodied creatures that don’t easily enter the geologic record. “The presence of so many stunning cnidarians was an absolute pleasure to see,” Daley says, referring to the jellyfish and sea anemones that thrived in this ancient ecosystem and are some of the key fossils that make the Qingjiang Biota stand out. “The significance of this site is in the way it fills several gaps in knowledge about key animal groups,” including cnidarians, strange invertebrates known as “mud dragons” and comb jellies. Representatives of all these groups are still alive today, making them some of the most ancient and successful animals in the world.

    This wealth of squishy-bodied specimens hasn’t been visible at other Cambrian sites. “The diversity of cnidarians and ctenophores and sponges seems unique and therefore may give us a lot of clues to the origin and evolution of these groups that other sites couldn’t,” Vinther says.

    The seeming flash fossilization of the Qingjiang Biota preserves an entire community of species, as close as paleontologists can get to time traveling back to 518 million years ago. “The fact that the assemblage of taxa is so different from other sites will also reveal the characteristics that influence what taxa live together in the same place at the same time,” Daley says, “and show us information about their ecological interactions.”

    The Qingjiang Biota also adds a new wrinkle to the ongoing fossiliferous debate about the Cambrian explosion. The “explosion” was a dramatic diversification of life during the Cambrian Period, but paleontologists are still discussing whether the evolutionary event was a real, sudden change or if it simply looks that way because of incomplete fossil sampling. While the Qingjiang Biota doesn’t necessarily resolve the debate, Daley says, it adds to the picture of amazing evolutionary radiation during the Cambrian.

    image: https://thumbs-prod.si-cdn.com/mWna73TVYMlYHnbEs_va90sIFIA=/fit-in/1072x0/https://public-media.si-cdn.com/filer/3c/11/3c11cb63-0158-4e38-a42c-aa7149cfe401/fu2hr.jpg

    Cambrian Fossils

    Digging up a Qingjiang fossil on a bank of the Danshui River, near its junction with the Qingjiang River, Hubei Province, China. (Dong King Fu)

    The fact that the Qingjiang Biota is about the same age as the nearby Chengjiang Biota, but contains many previously unknown species, indicates that the Cambrian hosted more unusual organisms than paleontologists previously imagined. The diversity of life at the time could be a signal of a much earlier flurry of evolutionary activity that gave rise to many new species preserved at sites like Qingjiang and the Burgess Shale.

    The study by Dongjing Fu and colleagues is a preliminary report, announcing the discovery of many species that have yet to be named and intensively studied. There may be more fossils out there as well. The researchers note that the geologic formation in which the Qingjiang Biota resides is found in other places in China and could yield additional fossils.

    The identities and interactions of the Qingjiang Biota creatures have yet to fully come into focus. For now, they offer a new window to a time we know little about, and, Daley says, “I can’t wait to see the detailed studies on these amazing fossils in the future.”

    Read more: https://www.smithsonianmag.com/science-nature/fossil-treasure-trove-ancient-animals-unearthed-china-180971769/#8SdhzFRgdbYrPMIS.99
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  • Stunning picture shows dead star racing away from a massive explosion

    Screen Shot 2019-03-22 at 8.03.28 AM

    Wooosh!Jayanne English, University of Manitoba; F. Schinzel et al.; NRAO/AUI/NSF; DRAO/Canadian Galactic Plane Survey; and NASA/IRAS.

    By Chelsea Whyte

    Need a kick-start? You would be hard-pressed to find one more powerful than a supernova – a sudden explosion in which a dying star ejects most of its mass. That is what happened to the pulsar pictured here, sending it racing away from its home with a tail of particles and magnetic energy stretching behind it for 13 light years. In the image above, the star is at the left end of the yellow tail and is heading away from the big bubble.

    “It’s very rare for a pulsar to get enough of a kick for us to see this,” said Frank Schinzel, of the National Radio Astronomy Observatory in Virginia, in a statement. He and his colleagues observed the pulsar – an extremely dense corpse of a star – with a radio telescope in New Mexico called the Very Large Array, and reported their results at a meeting of the American Astronomical Society in California.

    The pulsar is known as PSR J0002+6216 and is located 6500 light years from Earth. It is speeding away from the supernova at more than 1100 kilometres per second – much faster than most pulsars, which average about 240 kilometres per second, and enough to let it escape the Milky Way.

    The expanding debris initially outpaced the pulsar, but slowed as it met up with dust and gas in the surrounding space. After 5000 years, the pulsar caught up with edge of the supernova remnant and busted free. It has been another 5000 years since then, and the pulsar is now 53 light years away from the centre of the remnant.

  • Invisible X-rays

    Invisible X-rays

    This fuzzy orb of light is a giant elliptical galaxy filled with an incredible 200 billion stars. Unlike spiral galaxies, which have a well-defined structure and boast picturesque spiral arms, elliptical galaxies appear fairly smooth and featureless. This is likely why this galaxy, named Messier 49, was discovered by French astronomer Charles Messier in 1771. At a distance of 56 million light-years, and measuring 157 000 light-years across, M49 was the first member of the Virgo Cluster of galaxies to be discovered, and it is more luminous than any other galaxy at its distance or nearer.

    Elliptical galaxies tend to contain a larger portion of older stars than spiral galaxies and also lack young blue stars. Messier 49 itself is very yellow, which indicates that the stars within it are mostly older and redder than the Sun. In fact, the last major episode of star formation was about six billion years ago — before the Sun was even born!

    Messier 49 is also rich in globular clusters; it hosts about 6000, a number that dwarfs the 150 found in and around the Milky Way. On average, these clusters are 10 billion years old. Messier 49 is also known to host a supermassive black hole at its centre with the mass of more than 500 million Suns, identifiable by the X-rays pouring out from the heart of the galaxy (as this Hubble image comprises infrared observations, these X-rays are not visible here).

    Credit:

    ESA/Hubble & NASA, J. Blakenslee, P Cote et al.

  • Spread of cancers halted by smart bacteria that trigger immune attack

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    Bacteria can shrink cancer cells

    STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY

    By Michael Le Page Of New Scientist

    GENETICALLY modified “smart” bacteria injected into tumours can shrink growths and trigger an immune response that stops cancer spreading, tests in animals show.

    The engineered bacteria exploit the vulnerability of solid tumours to infections. This vulnerability comes about because tumours evolve all kinds of tricks for evading immune system attack, from physically keeping out immune cells to releasing chemicals that tell the cells not to attack. But this leaves tumours open to infection by bacteria and viruses that would be rapidly wiped out elsewhere in the body. …