April 05, 2016
  • A Japanese spacecraft's long-awaited Venus campaign is finally about to begin.

    Japan's Akatsuki probe was originally supposed to arrive at Venus in December 2010, but an engine failure caused the spacecraft to miss its target and zoom off into orbit around the sun. But this past December, Akatsuki's handlers managed to guide the craft back to Venus, and now the probe is just about ready to start science operations.

    "Akatsuki has been performing test observations by turning on its onboard observation instruments one by one," Japan Aerospace Exploration Agency (JAXA) officials wrote in an update on Friday (April 1).  [Japan at Venus: See the photos from Akatsuki]


    March 09, 2016
  • The first solar eclipse of 2016 occurred on March 8/9 and is the only total solar eclipse of the year. Learn more about that event below. The next one will be an annular solar eclipse (also known as a "ring of fire" solar eclipse) on Sept. 1, 2016.

    Main Story: Total Solar Eclipse Wows Skywatchers Across Indonesia, Pacific Region

    See photos of the 2016 total solar eclipse

    This photo of the partial solar eclipse of Sept. 13, 2015, was snapped by astrophotographer K.J. Mulder from his home in South Africa.

    This photo of the partial solar eclipse of Sept. 13, 2015, was snapped by astrophotographer K.J. Mulder from his home in South Africa.

    Credit: K.J. Mulder/Worlds in Ink


    A solar eclipse occurs when the moon gets between Earth and the sun, and the moon casts a shadow over Earth. A solar eclipse can only take place at the phase of new moon, when the moon passes directly between the sun and Earth and its shadows fall upon Earth’s surface. But whether the alignment produces a total solar eclipse, a partial solar eclipse or an annular solar eclipse depends on several factors, all explained below.

    The fact that an eclipse can occur at all is a fluke of celestial mechanics and time. Since the moon formed about 4.5 billion years ago, it has been gradually moving away from Earth (by about 1.6 inches, or 4 centimeters per year). Right now the moon is at the perfect distance to appear in our sky exactly the same size as the sun, and therefore block it out. But this is not always true.

    When is the next solar eclipse?

    The last solar eclipse was a total eclipse on March 20, 2015. [Related: Spectacular Solar Eclipse Kicks Off Spring]

    The next one will be a total solar eclipse on March 9, 2016 . According to Geoff Gaherty of Starry Night Education, the moon will be close to perigee for this eclipse, leading to a long period of totality, just over four minutes. The eclipse will begin over the Indian Ocean, and the moon’s shadow first makes landfall on the island of Sumatra, Indonesia.

    It then passes over Borneo, Sulawesi and Halmahera, before heading out into the Pacific Ocean, ending north of Hawaii. The partial eclipse will be visible over southern and eastern Asia, northern and western Australia, and much of the Pacific, including Hawaii. The times of maximum eclipse at major cities (Universal Time):

    • Darwin — 00:47
    • Fairbanks — 03:08
    • Guangzhou — 00:58
    • Ho Chi Minh — 00:34
    • Hong Kong — 00:58
    • Honolulu — 03:37
    • Jakarta — 00:22
    • Kuala Lumpur — 00:24
    • Madras — 00:51
    • Manila — 00:58
    • Phnom Pénh — 00:34
    • Singapore — 00:24
    • Tokyo — 02:09

    On Sept. 1, 2016, an annular eclipse will be visible over most of Africa, the southern Arabian Peninsula, and much of the Indian Ocean. Maximum eclipse occurs in Antarctica at 09:07 UT.

    Types of solar eclipses

    There are four types of solar eclipses: total, annular, partial and hybrid. Here’s what causes each type:

    Total solar eclipses

    These are a happy accident of nature. The sun's 864,000-mile diameter is fully 400 times greater than that of our puny moon, which measures just about 2,160 miles. But the moon also happens to be about 400 times closer to Earth than the sun (the ratio varies as both orbits are elliptical), and as a result, when the orbital planes intersect and the distances align favorably, the new moon can appear to completely blot out the disk of the sun. On the average a total eclipse occurs somewhere on Earth about every 18 months.

    There are actually two types of shadows: the umbra is that part of the shadow where all sunlight is blocked out. The umbra takes the shape of a dark, slender cone. It is surrounded by the penumbra, a lighter, funnel-shaped shadow from which sunlight is partially obscured.

    During a total solar eclipse, the moon casts its umbra upon Earth's surface; that shadow can sweep a third of the way around the planet in just a few hours. Those who are fortunate enough to be positioned in the direct path of the umbra will see the sun's disk diminish into a crescent as the moon's dark shadow rushes toward them across the landscape.

    During the brief period of totality, when the sun is completely covered, the beautiful corona — the tenuous outer atmosphere of the sun — is revealed. Totality may last as long as 7 minutes 31 seconds, though most total eclipses are usually much shorter.



    On Jan. 4, 2011, the moon passed in front of the sun in a partial solar eclipse - as seen from parts of Earth. Here, the joint Japanese-American Hinode satellite captured the same breathtaking event from space. The unique view created what's called an annular solar eclipse.

    On Jan. 4, 2011, the moon passed in front of the sun in a partial solar eclipse - as seen from parts of Earth. Here, the joint Japanese-American Hinode satellite captured the same breathtaking event from space. The unique view created what's called an annular solar eclipse.

    Credit: Hinode/XRT

    March 10, 2016
  • Don't panic, but our planet is doomed. It's just going to take a while. Roughly 6 billion years from now, the Earth will probably be vaporized when the dying Sun expands into a red giant and engulfs our planet.

    But the Earth is just one planet in the solar system, the Sun is just one of hundreds of billions of stars in the galaxy, and there are hundreds of billions of galaxies in the observable universe. What's in store for all of that? How does the universe end?

    The science is much less settled on how that will happen. We're not even sure if the universe will come to a firm, defined end, or just slowly tail off. Our best understanding of physics suggests there are several options for the universal apocalypse. It also offers some hints on how we might, just maybe, survive it.


    Our universe has been expanding since it began (Credit: Chris Butler/SPL)

    Our universe has been expanding since it began (Credit: Chris Butler/SPL)


    Our first clue to the end of the universe comes from thermodynamics, the study of heat. Thermodynamics is the wild-eyed street preacher of physics, bearing a cardboard placard with a simple warning: "THE HEAT DEATH IS COMING".

    The heat death is far worse than being burnt to a crisp

    Despite the name, the heat death of the universe isn't a fiery inferno. Instead, it's the death of all differences in heat.

    This may not sound scary, but the heat death is far worse than being burnt to a crisp. That's because nearly everything in everyday life requires some kind of temperature difference, either directly or indirectly.

    For instance, your car runs because it's hotter inside its engine than outside. Your computer runs on electricity from the local power plant, which probably works by heating water and using that to power a turbine. And you run on food, which exists thanks to the enormous temperature difference between the Sun and the rest of the universe.


    The universe will end in one of four ways (Credit: Carlos Clarivan/SPL)

    The universe will end in one of four ways (Credit: Carlos Clarivan/SPL)


    However, once the universe reaches heat death, everything everywhere will be the same temperature. That means nothing interesting will ever happen again.

    Heat death looked like the only possible way the universe could end

    Every star will die, nearly all matter will decay, and eventually all that will be left is a sparse soup of particles and radiation. Even the energy of that soup will be sapped away over time by the expansion of the universe, leaving everything just a fraction of a degree above absolute zero.

    In this "Big Freeze", the universe ends up uniformly cold, dead and empty.

    After the development of thermodynamics in the early 1800s, heat death looked like the only possible way the universe could end. But 100 years ago, Albert Einstein's theory of general relativity suggested that the universe had a far more dramatic fate.


    Galaxies like M74 are rushing away from us (Credit: Chris Butler/SPL)

    Galaxies like M74 are rushing away from us (Credit: Chris Butler/SPL)


    General relativity says that matter and energy warp space and time. This relationship between space-time and matter-energy (stuff) — between the stage and the actors on it — extends to the entire universe. The stuff in the universe, according to Einstein, determines the ultimate fate of the universe itself.

    The universe began as something incredibly small, and then expanded incredibly quickly

    The theory predicted that the universe as a whole must either be expanding or contracting. It could not stay the same size. Einstein realized this in 1917, and was so reluctant to believe it that he fudged his own theory.

    Then in 1929, the American astronomer Edwin Hubble found hard evidence that the universe was expanding. Einstein changed his mind, calling his previous insistence on a static universe the "greatest blunder" of his career.

    If the universe is expanding, it must once have been much smaller than it is now. This realization led to the Big Bang theory: the idea that the universe began as something incredibly small, and then expanded incredibly quickly. We can see the "afterglow" of the Big Bang even today, in the cosmic microwave background radiation – a constant stream of radio waves, coming from all directions in the sky.


    The cosmic microwave background (Credit: ESA Planck Collaboration/SPL)

    The cosmic microwave background (Credit: ESA Planck Collaboration/SPL)


    The fate of the universe, then, hinges on a very simple question: will the universe continue to expand, and how quickly?

    If there's too much stuff, the expansion of the universe will slow down and stop

    For a universe containing normal "stuff", such as matter and light, the answer to this question depends on how much stuff there is. More stuff means more gravity, which pulls everything back together and slows the expansion.

    As long as the amount of stuff doesn't go over a critical threshold, the universe will continue to expand forever, and eventually suffer heat death, freezing out.

    But if there's too much stuff, the expansion of the universe will slow down and stop. Then the universe will begin to contract. A contracting universe will shrink smaller and smaller, getting hotter and denser, eventually ending in a fabulously compact inferno, a sort of reverse Big Bang known as the Big Crunch.


    The universe might collapse on itself, in a "Big Crunch" (Credit: Mark Garlick/SPL)

    The universe might collapse on itself, in a "Big Crunch" (Credit: Mark Garlick/SPL)


    For most of the 20th century, astrophysicists weren't sure which of these scenarios would play out. Would it be the Big Freeze or the Big Crunch? Ice or fire?

    Dark energy pulls the universe apart

    They tried to perform a cosmic census, adding up how much stuff there is in our universe. It turned out that we're strangely close to the critical threshold, leaving our fate uncertain.

    That all changed at the end of the 20th century. In 1998, two competing teams of astrophysicists made an astonishing announcement: the expansion of the universe is speeding up.

    Normal matter and energy can't make the universe behave this way. This was the first evidence of a fundamentally new kind of energy, dubbed "dark energy", which didn't behave like anything else in the cosmos.

    Dark energy pulls the universe apart. We still don't understand what it is, but roughly 70% of the energy in the universe is dark energy, and that number is growing every day.


    The Big Crunch would bring our universe to a fiery end (Credit: Mehau Kulyk/SPL)

    The Big Crunch would bring our universe to a fiery end (Credit: Mehau Kulyk/SPL)


    The existence of dark energy means that the amount of stuff in the universe doesn't get to determine its ultimate fate.

    Instead, dark energy controls the cosmos, accelerating the expansion of the universe for all time. This makes the Big Crunch much less likely.

    But that doesn't mean that the Big Freeze is inevitable. There are other possibilities.

    One of them originated, not in the study of the cosmos, but in the world of subatomic particles. This is perhaps the strangest fate for the universe. It sounds like something out of science fiction, and in a way, it is.


    Water can sometimes stay liquid below its freezing point (Credit: Tomas Sobek, CC by 2.0)

    Water can sometimes stay liquid below its freezing point (Credit: Tomas Sobek, CC by 2.0)


    In Kurt Vonnegut's classic sci-fi novel Cat's Cradle, ice-nine is a new form of water ice with a remarkable property: it freezes at 46 °C, not at 0 °C. When a crystal of ice-nine is dropped into a glass of water, all the water around it immediately patterns itself after the crystal, since it has lower energy than liquid water.

    There's nowhere for the ice to start forming

    The new crystals of ice-nine do the same thing to the water around them, and in the blink of an eye, the chain reaction turns all the water in the glass — or (spoiler alert!) all of Earth's oceans — into solid ice-nine.

    The same thing can happen in real life with normal ice and normal water. If you put very pure water into a very clean glass, and cool it just below 0°C, the water will become supercooled: it stays liquid below its natural freezing point. There are no impurities in the water and no rough patches on the glass, so there's nowhere for the ice to start forming. But if you drop a crystal of ice into the glass, the water will freeze rapidly, just like ice-nine.

    Ice-nine and supercooled water may not seem relevant to the fate of the universe. But something similar could happen to space itself.


    Empty vacuum could suddenly drop to a lower energy level (Credit: Richard Kail/SPL)

    Empty vacuum could suddenly drop to a lower energy level (Credit: Richard Kail/SPL)


    Quantum physics dictates that even in a totally empty vacuum, there is a small amount of energy. But there might also be some other kind of vacuum, which holds less energy.

    The new vacuum will "convert" the old vacuum around it

    If that's true, then the entire universe is like a glass of supercooled water. It will only last until a "bubble" of lower-energy vacuum shows up.

    Fortunately, there are no such bubbles that we're aware of. Unfortunately, quantum physics also dictates that if a lower-energy vacuum is possible, then a bubble of that vacuum will inevitably dart into existence somewhere in the universe.

    When that happens, just like ice-nine, the new vacuum will "convert" the old vacuum around it. The bubble would expand at nearly the speed of light, so we'd never see it coming.


    Even completely empty space contains energy (Credit: Equinox Graphics/SPL)

    Even completely empty space contains energy (Credit: Equinox Graphics/SPL)


    Inside the bubble, things would be radically different, and not terribly hospitable.

    Humans, planets and even the stars themselves would be destroyed

    The properties of fundamental particles like electrons and quarks could be entirely different, radically rewriting the rules of chemistry and perhaps preventing atoms from forming.

    Humans, planets and even the stars themselves would be destroyed in this Big Change. In a 1980 paper, Physicists Sidney Coleman and Frank de Luccia called it "the ultimate ecological catastrophe".

    Adding insult to injury, dark energy would probably behave differently after the Big Change. Rather than driving the universe to expand faster, dark energy might instead pull the universe in on itself, collapsing into a Big Crunch.


    Phantom dark energy could destroy everything (Credit: Detlev van Ravenswaay/SPL)

    Phantom dark energy could destroy everything (Credit: Detlev van Ravenswaay/SPL)


    There is a fourth possibility, and once again dark energy is at centre stage. This idea is very speculative and unlikely, but it can't yet be ruled out. Dark energy might be even more powerful than we thought, and might be enough to end the universe on its own, without any intervening Big Change, Freeze, or Crunch.

    Dark energy has a peculiar property. As the universe expands, its density remains constant. That means more of it pops into existence over time, to keep pace with the increasing volume of the universe. This is unusual, but doesn't break any laws of physics.

    However, it could get weirder. What if the density of dark energy increases as the universe expands? In other words, what if the amount of dark energy in the universe increases more quickly than the expansion of the universe itself?

    This idea was put forward by Robert Caldwell of Dartmouth College in Hanover, New Hampshire. He calls it "phantom dark energy". It leads to a remarkably strange fate for the universe.


    The Big Rip would begin by tearing galaxies apart (Credit: Detlev van Ravenswaay/SPL)

    The Big Rip would begin by tearing galaxies apart (Credit: Detlev van Ravenswaay/SPL)


    If phantom dark energy exists, then the dark side is our ultimate downfall, just like Star Wars warned us it would be.

    Atoms themselves would shatter, a fraction of a second before the universe itself ripped apart

    Right now, the density of dark energy is very low, far less than the density of matter here on Earth, or even the density of the Milky Way galaxy, which is much less dense than Earth. But as time goes on, the density of phantom dark energy would build up, and tear the universe apart.

    In a 2003 paper, Caldwell and his colleagues outlined a scenario they called "cosmic doomsday". Once the phantom dark energy becomes more dense than a particular object, that object gets torn to shreds.

    First, phantom dark energy would pull the Milky Way apart, sending its constituent stars flying. Then the solar system would be unbound, because the pull of dark energy would be stronger than the pull of the Sun on the Earth.

    Finally, in a few frantic minutes the Earth would explode. Then atoms themselves would shatter, a fraction of a second before the universe itself ripped apart. Caldwell calls this the Big Rip.


    The Big Rip would literally tear planets and stars apart (Credit: Nicolle R. Fuller/SPL)

    The Big Rip would literally tear planets and stars apart (Credit: Nicolle R. Fuller/SPL)


    The Big Rip is, by Caldwell's own admission, "very outlandish" – and not just because it sounds like something out of an over-the-top superhero comic.

    This is a remarkably grim portrait of the future

    Phantom dark energy flies in the face of some fairly basic ideas about the universe, like the assumption that matter and energy can't go faster than the speed of light. There are good reasons not to believe in it.

    Based on our observations of the expansion of the universe, and particle physics experiments, it seems much more likely that the ultimate fate of our universe is a Big Freeze, possibly followed by a Big Change and a final Big Crunch.

    But this is a remarkably grim portrait of the future — aeons of cold emptiness, finally terminated by a vacuum decay and a final implosion into nothingness. Is there any escape? Or are we doomed to book a table at the Restaurant at the End of the Universe?


    All this shall pass, but not for a very long time (Credit: Allan Morton/Dennis/Milon/SPL)

    All this shall pass, but not for a very long time (Credit: Allan Morton/Dennis/Milon/SPL)


    There's certainly no reason for us, individually, to worry about the end of the universe. All of these events are trillions of years into the future, with the possible exception of the Big Change, so they're not exactly an imminent problem.

    Also, there's no reason to worry about humanity. If nothing else, genetic drift will have rendered our descendants unrecognizable long before then. But could intelligent feeling creatures of any kind, human or not, survive?

    If the universe is accelerating, that's really bad news

    Physicist Freeman Dyson of the Institute for Advanced Studies in Princeton, New Jersey considered this question in a classic paper published in 1979. At the time, he concluded that life could modify itself to survive the Big Freeze, which he thought was less challenging than the inferno of the Big Crunch.

    But these days, he's much less optimistic, thanks to the discovery of dark energy.

    "If the universe is accelerating, that's really bad news," says Dyson. Accelerating expansion means we'll eventually lose contact with all but a handful of galaxies, dramatically limiting the amount of energy available to us. "It's a rather dismal situation in the long run."

    The situation could still change. "We really don't know whether the expansion is going to continue since we don't understand why it's accelerating," says Dyson. "The optimistic view is that the acceleration will slow down as the universe gets bigger." If that happens, "the future is much more promising."

    But what if the expansion doesn't slow down, or if it becomes clear that the Big Change is coming? Some physicists have proposed a solution that is solidly in mad-scientist territory. To escape the end of the universe, we should build our own universe in a laboratory, and jump in.


    Just after it was born, the universe inflated rapidly (Credit: David Parker/SPL)

    Just after it was born, the universe inflated rapidly (Credit: David Parker/SPL)


    One physicist who has worked on this idea is Alan Guth of MIT in Cambridge, Massachusetts, who is known for his work on the very early universe.

    You would jump-start the creation of an entirely new universe

    "I can't say that the laws of physics absolutely imply that it's possible," says Guth. "If it is possible, it would require technology vastly beyond anything that we can foresee. It would require huge amounts of energy that one would need to be able to obtain and control."

    The first step, according to Guth, would be creating an incredibly dense form of matter — so dense that it was on the verge of collapsing into a black hole. By doing that in the right way, and then quickly clearing the matter out of the area, you might be able to force that region of space to start expanding rapidly.

    In effect, you would jump-start the creation of an entirely new universe. As the space in the region expanded, the boundary would shrink, creating a bubble of warped space where the inside was bigger than the outside.


    The Big Bang: the birth of a universe (Credit: Detlev van Ravenswaay/SPL)

    The Big Bang: the birth of a universe (Credit: Detlev van Ravenswaay/SPL)


    That may sound familiar to Doctor Who fans, and according to Guth, the TARDIS is "probably a very accurate analogy" for the kind of warping of space he's talking about.

    We don't really know if it's possible or not

    Eventually, the outside would shrink to nothingness, and the new baby universe would pinch off from our own, spared from whatever fate our universe may meet.

    It's far from certain that this scheme would actually work. "I would have to say that it's unclear," says Guth. "We don't really know if it's possible or not."

    However, Guth also points out that there is another source of hope beyond the end of the universe – well, hope of a sort.


    Other universe may be appearing all the time (Credit: Detlev van Ravenswaay/SPL)

    Other universe may be appearing all the time (Credit: Detlev van Ravenswaay/SPL)


    Guth was the first to propose that the very early universe expanded astonishingly fast for a tiny fraction of a second, an idea known as "inflation". Many cosmologists now believe inflation is the most promising approach for explaining the early universe, and Guth's plan for creating a new universe relies on recreating this rapid expansion.

    The multiverse as a whole is genuinely eternal

    Inflation has an intriguing consequence for the ultimate fate of the universe. The theory dictates that the universe we inhabit is just one small part of a multiverse, with an eternally inflating background continually spawning "pocket universes" like our own.

    "If that's the case, even if we're convinced that an individual pocket universe will ultimately die through refrigeration, the multiverse as a whole will go on living forever, with new life being created in each pocket universe as it's created," says Guth. "In this picture, the multiverse as a whole is genuinely eternal, at least eternal into the future, even as individual pocket universes live and die."

    In other words, Franz Kafka may have been right on the money when he said that there is "plenty of hope, an infinite amount of hope—but not for us."

    March 10, 2016
  • Extraterrestrial life[n 1] is life that does not originate from Earth. It is also called alien life, or, if it is a sentient and/or relatively complex individual, an "extraterrestrial" or "alien" (or, to avoid confusion with the legal sense of "alien", a "space alien"). These as-yet-hypothetical life forms range from simple bacteria-like organisms to beings with civilizations far more advanced than humanity. Although many scientists expect extraterrestrial life to exist, there is no unambiguous evidence for its existence so far.

    The science of extraterrestrial life is known as exobiology. The science of astrobiology also considers life on Earth as well, and in the broader astronomical context. Meteorites that have fallen to Earth have sometimes been examined for signs of microscopic extraterrestrial life. In 2015, "remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia, when the young Earth was about 400 million years old. According to one of the researchers, "If life arose relatively quickly on Earth ... then it could be common in the universe."

    Since the mid-20th century, there has been an ongoing search for signs of extraterrestrial intelligence, from radios used to detect possible extraterrestrial signals, to telescopes used to search for potentially habitable extrasolar planets. It has also played a major role in works of science fiction. Over the years, science fiction works, especially Hollywood's involvement, has increased the public's interest in the possibility of extraterrestrial life. Some encourage aggressive methods to try to get in contact with life in outer space, whereas others argue that it might be dangerous to actively call attention to Earth.

    March 10, 2016
  • A fireball exploded over the south Atlantic Ocean on Feb. 6 in the most powerful such event since February 2013, when a similar "airburst" injured more than 1,200 people in the Russian city of Chelyabinsk.

    Last month's fireball packed the energy equivalent of 13,000 tons (13 kilotons) of TNT, but it exploded in a remote location, so no eyewitness reports are known. (The event was recorded on NASA's Fireball and Bolide Reports page.)

    Meteors burn up in Earth's atmosphere every day, but most are small and therefore fly completely under the radar. Fireballs as dramatic as the Feb. 6 event — which was caused by an object estimated to be 16 to 23 feet (5 to 7 meters) wide — occur about once every two to three years, according to Peter Brown, a professor at the University of Western Ontario in Canada and a member of the Western Meteor Physics Group. [Photos: Russian Meteor Explosion of Feb. 15, 2013]

    The Feb. 6 fireball, while powerful, would probably not have caused damage even if it had hit Earth over a populated area, Brown added.

    "The only way you might get damaged is if rocks hit the ground and you are unlucky enough to be hit by some debris," he told 

    Brownincoming ly. 

    The object that exploded above Chelyabinsk three years ago was about 65 feet (20 m) wide, experts say, and had an estimated explosive energy of 500 kilotons. The blast shattered hundreds of windows; the reported injuries were almost all caused by shards of flying glass.

    Meteor terminology can get confusing, so here's a quick primer: An asteroid is a space rock. A meteoroid is a space rock about to hit Earth, a meteor is a space rock burning in Earth's atmosphere, and a meteorite is a space rock that made it all the way to the ground. (And, technically speaking, a fireball is a meteor that shines at least as brightly as the planet Venus in the sky.) 

    Varying damage potential
    Meteoroids can come in several different forms. A small percentage of them (perhaps 5 percent) are made of solid iron. Others are more like comets — collections of ice and dust — and still others are rubble piles composed of bits of rock, dust and ice.

    If the meteoroid is solid iron and large enough, a fraction of it can survive its trip through Earth's atmosphere and make it all the way to the ground, Brown said. A more loosely-held-together meteoroid, however, will break up in the air.

    Both the Chelyabinsk rock and the Feb. 6 object likely came into the atmosphere at a shallow angle of about 20 degrees, subjecting each to relatively little heating and allowing each to penetrate deep into the atmosphere. Both rocks also each exploded at about 19 miles (30 kilometers) above the ground.

    A much more powerful airburst took place over the Tunguska region of Siberia on June 30, 1908, flattening about 770 square miles (2,000 square km) of forest. 

    The best current estimates, Brown said, have the Tunguska object exploding with a force of between 5 and 15 megatons, or about 10 to 30 times the total energy of Chelyabinsk. Experts think the Tunguska meteor was at least 100 feet (30 m) wide, and they believe it detonated about three times closer to the ground than the Chelyabinsk object did — between 4.3 to 6.2 miles (7 to 10 km) above the Siberian treetops. [What If Tunguska Event Happened Over New York City? (Video)] 

    Tough to track
    NASA and other agencies have a robust asteroid-tracking program that can detect objects about 16 to 32 feet (5 to 10 m) wide depending on their proximity to Earth, lighting conditions and other factors. 

    So far, surveys have found two asteroids of this size shortly before they impacted Earth: 2008 TC3, which came in over Sudan in 2008, and 2014 AA, which impacted over the middle of the Atlantic Ocean on Jan. 2, 2014.

    The main observatories for this work, Brown said, are the University of Arizona's Catalina Sky Survey and the University of Hawaii's Pan-STARRS (Panoramic Survey Telescope & Rapid Response System). Catalina found both 2008 TC3 and 2014 AA. Both Catalina and Pan-STARRS are continually improving their capabilities and will likely be able to detect more objects of this type in the coming years, he said.

    Also coming online in the next few months the University of Hawaii's Asteroid Terrestrial-impact Last Alert System (ATLAS). This asteroid-detection system is optimized to pick up meteoroids impacting Earth, and will scan the sky a couple of times a night in search of them. The aim is to give a few days' or weeks' notice ahead of an impact. 

    But such tracking efforts are concerned primarily with big, potentially dangerous objects, not small fry like the one that caused the Feb. 6 airburst.

    "They are too hard to detect ahead of impacting Earth’s atmosphere, and almost never do any damage — Chelyabinsk being a notable exception," Lindley Johnson, lead program executive at NASA's newly created Planetary Defense Coordination Office (PDCO), told via email. 

    "This size object hit and no one noticed," Johnson added, referring to the Feb. 6 rock. "Except we in the NASA PDCO did and put it on our fireball reports page, and that’s why everyone now knows about it."

    Follow Elizabeth Howell @howellspace, or @Spacedotcom. We're also on Facebook and Google+. Originally published on


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    March 10, 2016
  • NASA Targets May 2018 Launch of Mars InSight Mission

    Artist's concept of InSight

    NASA has set a new launch opportunity, beginning May 5, 2018, for the InSight mission to Mars. This artist's concept depicts the InSight lander on Mars after the lander's robotic arm has deployed a seismometer and a heat probe directly onto the ground. InSight is the first mission dedicated to investigating the deep interior of Mars. The findings will advance understanding of how all rocky planets, including Earth, formed and evolved.

    Credits: NASA/JPL-Caltech

    NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission to study the deep interior of Mars is targeting a new launch window that begins May 5, 2018, with a Mars landing scheduled for Nov. 26, 2018.


    InSight’s primary goal is to help us understand how rocky planets – including Earth – formed and evolved. The spacecraft had been on track to launch this month until a vacuum leak in its prime science instrument prompted NASA in December to suspend preparations for launch.


    InSight project managers recently briefed officials at NASA and France's space agency, Centre National d'Études Spatiales (CNES), on a path forward; the proposed plan to redesign the science instrument was accepted in support of a 2018 launch.


    “The science goals of InSight are compelling, and the NASA and CNES plans to overcome the technical challenges are sound," said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington. "The quest to understand the interior of Mars has been a longstanding goal of planetary scientists for decades. We’re excited to be back on the path for a launch, now in 2018.”  


    NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, will redesign, build and conduct qualifications of the new vacuum enclosure for the Seismic Experiment for Interior Structure (SEIS), the component that failed in December. CNES will lead instrument level integration and test activities, allowing the InSight Project to take advantage of each organization’s proven strengths. The two agencies have worked closely together to establish a project schedule that accommodates these plans, and scheduled interim reviews over the next six months to assess technical progress and continued feasibility. 


    The cost of the two-year delay is being assessed. An estimate is expected in August, once arrangements with the launch vehicle provider have been made. 


    The seismometer instrument's main sensors need to operate within a vacuum chamber to provide the exquisite sensitivity needed for measuring ground movements as small as half the radius of a hydrogen atom. The rework of the seismometer's vacuum container will result in a finished, thoroughly tested instrument in 2017 that will maintain a high degree of vacuum around the sensors through rigors of launch, landing, deployment and a two-year prime mission on the surface of Mars.


    The InSight mission draws upon a strong international partnership led by Principal Investigator Bruce Banerdt of JPL. The lander's Heat Flow and Physical Properties Package is provided by the German Aerospace Center (DLR). This probe will hammer itself to a depth of about 16 feet (five meters) into the ground beside the lander.


    SEIS was built with the participation of the Institut de Physique du Globe de Paris and the Swiss Federal Institute of Technology, with support from the Swiss Space Office and the European Space Agency PRODEX program; the Max Planck Institute for Solar System Research, supported by DLR; Imperial College, supported by the United Kingdom Space Agency; and JPL.


    "The shared and renewed commitment to this mission continues our collaboration to find clues in the heart of Mars about the early evolution of our solar system," said Marc Pircher, director of CNES's Toulouse Space Centre.


    The mission’s international science team includes researchers from Austria, Belgium, Canada, France, Germany, Japan, Poland, Spain, Switzerland, the United Kingdom and the United States.


    JPL manages InSight for NASA's Science Mission Directorate. InSight is part of NASA's Discovery Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama. The InSight spacecraft, including cruise stage and lander, was built and tested by Lockheed Martin Space Systems in Denver. It was delivered to Vandenberg Air Force Base, California, in December 2015 in preparation for launch, and returned to Lockheed Martin's Colorado facility last month for storage until spacecraft preparations resume in 2017.


    NASA is on an ambitious journey to Mars that includes sending humans to the Red Planet, and that work remains on track. Robotic spacecraft are leading the way for NASA’s Mars Exploration Program, with the upcoming Mars 2020 rover being designed and built, the Opportunity and Curiosity rovers exploring the Martian surface, the Odyssey and Mars Reconnaissance Orbiter spacecraft currently orbiting the planet, along with the Mars Atmosphere and Volatile Evolution Mission (MAVEN) orbiter, which is helping scientists understand what happened to the Martian atmosphere.

    NASA and CNES also are participating in ESA’s (European Space Agency's) Mars Express mission currently operating at Mars. NASA is participating on ESA’s 2016 and 2018 ExoMars missions, including providing telecommunication radios for ESA's 2016 orbiter and a critical element of a key astrobiology instrument on the 2018 ExoMars rover.

    October 01, 2016
  • On Tuesday (Sept. 27), billionaire entrepreneur Elon Musk outlined plans to get hundreds of people to Mars. But are those plans really feasible? 

    Musk, who is founder and CEO of the private spaceflight company SpaceX, outlined a plan to build spacecraft that could each transport on the order of 100 people to the Red Planet. The plan would also include a giant new SpaceX rocket, spacecraft and support systems to help get those people to Mars (or destinations beyond). The even-longer-term goal that tops off Musk's vision is for humans alter Mars' atmosphere and environment to make the planet hospitable to life. 

    The plan is ambitious in nearly every way, from the technology Musk presented to the time line on which he hopes to accomplish these goals, not to mention the funding that will be required. Even so, the experts we talked to said it doesn't seem impossible, or even unachievable.[Images: SpaceX's Interplanetary Transport for Mars Colonization]

    October 24, 2016
  • Weird waves in Uranus' rings suggest there might be two tiny, unknown moonlets orbiting there.

    Researchers know little about the distant, icy planet Uranus compared to other planets in the solar system. Only one spacecraft has flown by it, Voyager 2 in 1986, and scientists have pieced together the rest of their observations through views from Earth-based and orbiting telescopes. The planet has rings — narrower and much darker in color than most of Saturn's, with uneven widths and strange, sharp edges — and is tilted dramatically on its side, giving rise to decades-long seasons and extreme weather patterns.

    Uranus has a crowded consortium of at least 27 moons named for literary figures, some orbiting in tight, unstable-looking formations. And now, new analysis of data from the Voyager 2 flyby suggests that two more tiny moons lurk even closer to the planet than those already known.