This image taken by NASA's Spitzer Space Telescope shows the comet Encke riding along its pebbly trail of debris. Every October, Earth passes through Encke's wake, resulting in the well-known Taurid meteor shower.
As comets travel along their orbit they dump material along the way. A stream of debris known as the Taurid swarm has been keeping astronomers attention. It’s thought the debris is the remains of comet Encke which has also been fuelling the Taurid meteor shower. The swarm is believed to be composed of mostly harmless, tiny objects but there has been concern that there may be some larger, kilometre size chunks. Thankfully, new observations reveal there are of the order of 9-14 of these 1km rocks.
Before you read the rest of this article know there are no known threats to life on Earth! We shouldn’t sit complacently on this tiny rock in space though so NASA have been working on ways to neutralise potential asteroid threats should they arise. The DART mission proved it was possible to alter the trajectory of an asteroid in space. Direct impact though where a probe smashes into the rock is one way but potentially not the best. A team of researchers have now been exploring ways that a nuclear explosion near an asteroid may send a blast of X-rays sufficiently powerful to vaporise material generating thrust to redirect the asteroid.
Mining asteroids might be necessary for humanity to expand into the Solar System. But what effect would asteroid mining have on the world's economy? Credit: ESA.
Gazing at the night sky can evoke a sense of wonder regarding humanity’s place in the Universe. But that’s not all it can evoke. If you’re knowledgeable about asteroid strikes like the one that wiped out the dinosaurs, then even a fleeting meteorite can nudge aside your enjoyable sense of wonder. What if?
Luckily, planetary defence is at the top of mind for some scientists and engineers. One of those scientists is Professor Philip Lubin from the University of California Santa Barbara. Lubin is developing his idea called PI-Terminal Defense for Humanity. The PI stands for Pulverize It, and Lubin thinks pulverizing an incoming impactor into tiny pieces is our best bet to protect ourselves from an asteroid on short notice.
Mocked up illustration of touchdown impact on Antarctica. Credit: Mark A. Garlick.
The effects of ancient asteroid impacts on Earth are still evident from the variety of impact craters across our planet. And from the Chelyabinsk event back in 2013, where an asteroid exploded in the air above a Russian town, we know how devastating an “airburst” event can be.
Now, researchers in Antarctica have discovered evidence of a strange intermediate-type event – a combination of an impact and an airburst. The event was so devastating, its effects are still apparent even though it took place 430,000 years ago.
Incoming: The Earth-Moon system has company tonight.
The Asteroid: Near Earth Asteroid 2010 WC9 is back. Discovered by the Catalina Sky Survey outside Tucson, Arizona on November 30th, 2010, this asteroid was lost after a brief 10 day observation window and was not recovered until just earlier this month. About 71 meters in size, 2010 WC9 is one of the largest asteroids to pass us closer than the Earth-Moon distance.
A closeup of the passage of asteroid 2010 WC9 through the Earth-Moon system on May 15th. Credit: NASA-JPL
2010 WC9 poses no threat to the Earth. About the size of the Statue of Liberty from the ground level to her crown, the asteroid is over three times bigger than the one that exploded over Chelyabinsk, Russia on the morning of February 15th, 2013.
The view from asteroid 2010 WC9 on closest approach. Credit: Starry Night
The Pass: 2010 WC9 passes just 0.5 times the Earth-Moon distance (126,500 miles or 203,500 kilometers) on Tuesday, May 15th at 22:05 UT/6:05 PM EDT. That’s only roughly five times the distance of satellites in geosynchronous orbit. The asteroid is also a relative fast mover, whizzing by at over 12 kilometers per second. An Apollo-type asteroid, 2010 WC9 orbits the Sun once every 409 days, ranging from a perihelion of 0.78 astronomical units (AU) outside the orbit of Venus out to 1.38 AU, just inside the orbit of Mars. This is the closest passage of the asteroid by the Earth for this century.
The passage of asteroid 2010 WC9 through the constellation Ophiuchus on May 15th from 00:00 to 16:00 UT. Credit Starry Night.
Observing: This one grabbed our attention when it cropped up on the Space Weather page for close asteroid passes this past weekend: a large, fast mover passing close to the Earth is a true rarity. At closest approach, 2010 WC9 will be moving at 0.22 degrees (that’s 13 arcminutes, about half the span of a Full Moon) per minute through the constellation Pavo the Peacock shining at magnitude +10, making it a good telescopic object for observers based in South Africa as it heads over the South Pole.
The southern hemisphere passage of asteroid 2010 WC9 on May 15th from 19:00 to 23:00 UT.
North American and European observers get their best look at the asteroid tonight into early tomorrow morning while it’s still twice the distance of the Moon, shining at 13th magnitude and moving southward through the constellation Ophiuchus and across the ecliptic plane.
The best strategy to ambush the space rock is to simply aim a low power field of view at the right coordinates at the right time (see below), and watch. You should be able to see the asteroid moving slowly against the starry background, in real time.
Keep in mind, the charts we made here are geocentric, assuming you’re observing from the center of the Earth. Parallax comes into play on a close asteroid pass, and the Earth’s gravity will deflect 2010 WC9’s orbit considerably. Your best bet for generating a refined track for the asteroid is to use NASA JPL’s Horizons web interface to generate Right Ascension/Declination coordinates for the 2010 WC9 for your location.
How do you ‘lose an asteroid?” Often, an initial observation arc for a distant asteroid is too short to pin down a refined orbit. We have a blind spot sunward, for example, and fast moving asteroids can also be difficult to track across rich star fields and movement from one celestial hemisphere to the next. Recovery of 2010 WC9 earlier this month now gives us a solid seven year observation arc to peg its orbit down to a high accuracy.
Clouded out, or live in the wrong hemisphere? Slooh will carry an observing session for 2010 WC9 starting tonight at 24:00 UT/ 8:00 PM EDT. The Northholt Branch Observatories in London, England will also stream the pass live via Facebook tonight. Check their page for a start time.
Children ice skating in Khakassia, Russia react to the fall of a bright fireball two nights ago on Dec.6
In 1908 it was Tunguska event, a meteorite exploded in mid-air, flattening 770 square miles of forest. 39 years later in 1947, 70 tons of iron meteorites pummeled the Sikhote-Alin Mountains, leaving more than 30 craters. Then a day before Valentine’s Day in 2013, hundreds of dashcams recorded the fiery and explosive entry of the Chelyabinsk meteoroid, which created a shock wave strong enough to blow out thousands of glass windows and litter the snowy fields and lakes with countless fusion-crusted space rocks.
Documentary footage from 1947 of the Sikhote-Alin fall and how a team of scientists trekked into the wilderness to find the craters and meteorite fragments
Now on Dec. 6, another fireball blazed across Siberian skies, briefly illuminated the land like a sunny day before breaking apart with a boom over the town of Sayanogorsk. Given its brilliance and the explosions heard, there’s a fair chance that meteorites may have landed on the ground. Hopefully, a team will attempt a search soon. As long as it doesn’t snow too soon after a fall, black stones and the holes they make in snow are relatively easy to spot.
This photo shows trees felled from a powerful aerial meteorite explosion. It was taken during Leonid Kulik’s 1929 expedition to the Tunguska impact event in Siberia in 1908. Credit: Kulik Expedition
OK, maybe Siberia doesn’t get ALL the cool fireballs and meteorites, but it’s done well in the past century or so. Given the dimensions of the region — it covers 10% of the Earth’s surface and 57% of Russia — I suppose it’s inevitable that over so vast an area, regular fireball sightings and occasional monster meteorite falls would be the norm. For comparison, the United States covers only 1.9% of the Earth. So there’s at least a partial answer. Siberia’s just big.
A naturally sculpted iron-nickel meteorite recovered from the Sikhote-Alin meteorite fall in February 1947. The dimpling or “thumb-printing” occurs when softer minerals are melted and sloughed away as the meteorite is heated by the atmosphere while plunging to Earth. Credit: Svend Buhl
Every day about 100 tons of meteoroids, which are fragments of dust and gravel from comets and asteroids, enter the Earth’s atmosphere. Much of it gets singed into fine dust, but the tougher stuff — mostly rocky, asteroid material — occasionally makes it to the ground as meteorites. Every day then our planet gains about a blue whale’s weight in cosmic debris. We’re practically swimming in the stuff!
Meteors are pieces of comet and asteroid debris that strike the atmosphere and burn up in a flash. Here, a brilliant Perseid meteor streaks along the Summer Milky Way this past August. Credit: Jeremy Perez
Most of this mass is in the form of dust but a study done in 1996 and published in the Monthly Notices of the Royal Astronomical Society further broke down that number. In the 10 gram (weight of a paperclip or stick of gum) to 1 kilogram (2.2 lbs) size range, 6,400 to 16,000 lbs. (2900-7300 kilograms) of meteorites strike the Earth each year. Yet because the Earth is so vast and largely uninhabited, appearances to the contrary, only about 10 are witnessed falls later recovered by enterprising hunters.
A couple more videos of the Dec. 6, 2016 fireball over Khakassia and Sayanogorsk, Russia
Meteorites fall in a pattern from smallest first to biggest last to form what astronomers call a strewnfield, an elongated stretch of ground several miles long shaped something like an almond. If you can identify the meteor’s ground track, the land over which it streaked, that’s where to start your search for potential meteorites.
Meteorites indeed fall everywhere and have for as long as Earth’s been rolling around the sun. So why couldn’t just one fall in my neighborhood or on the way to work? Maybe if I moved to Siberia …
36 years ago today, a strange event was detected over the Southern Indian Ocean that remains controversial. On September 22nd, 1979, an American Vela Hotel satellite detected an atmospheric explosion over the southern Indian Ocean near the Prince Edward Islands. The event occurred at 00:53 Universal Time on the pre-dawn nighttime side of the Earth. Vela’s gamma-ray and x-ray detectors rang out in surprise, along with its two radiometers (known as Bhangmeters) which also captured the event.
The approximate location of the flash seen by the Vela-5b satellite Image credit: Wikimedia Commons/public domain
What was it?
Even today, the source of the Vela Incident remains a mystery. Designed to detect nuclear detonations worldwide and enforce the Partial Nuclear Test Ban Treaty, the Vela satellites operated for about ten years and were also famous for discovering evidence for extra-galactic gamma-ray bursts.
A Vela payload in the lab. Image credit: The U.S. Department of Defense
Vela-5B was the spacecraft from the series that detected the mysterious flash. A Titan-3C rocket launched Vela 5B (NORAD ID 1969-046E) on May 23rd, 1969 from Vandenberg Air Force Base in California.
One of the first things scientists realized early on in the Cold War is that the Universe is a noisy place, and that this extends across the electromagnetic spectrum. Meteors, lightning, cosmic rays and even distant astrophysical sources can seem to mimic certain signature aspects of nuclear detonations. The ability to discern the difference between human-made and natural events became of paramount importance and remains so to this day: the hypothetical scenario of a Chelyabinsk-style event over two nuclear armed states already on a political hair-trigger edge is a case in point.
Over the years, the prime suspect for the Vela Incident has been a joint South African-Israeli nuclear test. The chief piece of evidence is the characteristic ‘double-flash’ recorded by Vela, characteristic of a nuclear detonation. Said event would’ve been an approximately 3 kiloton explosion; for context, the bomb dropped on Hiroshima had a 15 kiloton yield, and the Chelyabinsk event had an estimated equivalent explosive force of 500 kilotons. As a matter of fact, the Vela Incident became a topic of discussion on the day Chelyabinsk occurred, as we sought to verify the assertion of whether Chelyabinsk was ‘the biggest thing’ since the 1908 Tunguska event.
A bolide event captured over Pennsylvania in early 2015. Image credit: Bill Ingalls/NASA
The Carter administration played down the Vela Incident at the time, though U.S. Air Force dispatched several WC-135B surveillance aircraft to the area, which turned up naught. Though detectors worldwide reported no increase of radioactive fallout, the ionospheric observatory at Arecibo did detect an atmospheric wave on the same morning as the event.
Israel ratified the Limited Test Ban Treaty in 1964. To date, Israel has never acknowledged that the test took place or the possession of nuclear weapons. Over the years, other suspect states have included Pakistan, France and India. Today, probably the only true final confirmation would come from someone stepping forward who was directly involved with the test, as it must have required the silence of a large number of personnel.
A comparison of the Vela event with a known nuclear test and a typical “zoo event’. Image credit: Vela Event Alert 747, Los Alamos Nat’l Laboratory
Was it a reentry or a bolide? Again, the signature double flash seen by the Vela satellite makes it unlikely. A micrometeoroid striking the spacecraft could have caused an anomalous detection known as a ‘zoo event,’ mimicking a nuclear test. Los Alamos researchers who have analyzed the event over the years remain convinced in the assertion that the 1979 Vela Incident had all the hallmark signatures of a nuclear test.
A U.S. nuclear detonation during Operation Upshot-Knothole in 1953. Image credit: National Nuclear Security Administration/Public Domain
Shortly after the Cold War, the U.S. Department of Defense made much of its atmospheric monitoring data public, revealing that small meteorites strike us much more often than realized. Sadly, this type of continual monitoring accompanied by public data release has declined in recent years mostly due to budgetary concerns, though monitoring of the worldwide environment for nuclear testing via acoustic microphone on land, sea and eyes overhead in space continues.
And it’s frightening to think how close we came to a nuclear exchange during the Cold War on several occasions. For example: in 1960, an Distant Early Warning System based in Thule, Greenland mistook the rising Moon for a Soviet missile launch (!) The United States also conducted nuclear tests in space shortly before the Test Ban Treaty went into effect, including Starfish Prime:
The Vela Incident remains a fascinating chapter of the Cold War, one where space and the geopolitical intrigue overlap. Even today, parsing out the difference between human-made explosions and the cataclysmic events that pepper the cosmos remains a primary concern for the continued preservation of our civilization.
Tactical nuclear weapons from around the world seen on display at the Nuclear Science Museum in Albuquerque, New Mexico. Image credit: Dave Dickinson
-Listen to an interesting discussion on monitoring nuclear plants worldwide via neutrino emissions.
-For a fascinating in-depth discussion on the continued relevance of the Vela Incident, check out this recent article by The Bulletin of Atomic Scientists.
All right, sure – there are a lot of asteroids that don’t hit us. And of course quite a few that do… Earth is impacted by around 100 tons of space debris every day (although that oft-stated estimate is still being researched.) But on March 10, 2015, a 12–28 meter asteroid dubbed 2015 ET cosmically “just missed us,” zipping past Earth at 0.3 lunar distances – 115,200 kilometers, or 71, 580 miles.*
The video above shows the passage of 2015 ET across the sky on the night of March 11–12, tracked on camera from the Crni Vrh Observatory in Slovenia. It’s a time-lapse video (the time is noted along the bottom) so the effect is really neat to watch the asteroid “racing along” in front of the stars… but then, it was traveling a relative 12.4 km/second!
UPDATE 3/14: As it turns out the object in the video above is not 2015 ET; it is a still-undesignated NEO. (My original source had noted this incorrectly as well.) Regardless, it was an almost equally close pass not 24 hours after 2015 ET’s! Double tap. (ht to Gerald in the comments.) UPDATE #2: The designation for the object above is now 2015 EO6.
This diagram maps data gathered from 1994-2013 on small asteroids impacting Earth's atmosphere to create very bright meteors (bolides). The location of impacts from objects ranging from 1 meter (3 feet) to nearly 20 meters (60 feet) in size such as Chelyabinsk asteroid are shown globally. (Credit: Planetary Science, NASA)
How hazardous are the thousands and millions of asteroids that surround the third rock from the Sun – Earth? Since an asteroid impact represents a real risk to life and property, this is a question that has been begging for answers for decades. But now, scientists at NASA’s Jet Propulsion Laboratory have received data from a variety of US Department of Defense assets and plotted a startling set of data spanning 20 years.
This latest compilation of data underscores how frequent some of these larger fireballs are, with the largest being the Chelyabinsk event on February 15, 2013 which injured thousands in Russia. The new data will improve our understanding of the frequency and presence of small and large asteroids that are hazards to populated areas anywhere on Earth.
On Feb. 28, 2009, Peter Jenniskens (SETI/NASA), finds his first 2008TC3 meteorite after an 18-mile long journey. “It was an incredible feeling,” Jenniskens said. The meteorite which impacted in the Nubian Desert of Africa on Oct 7, 2008 was the first asteroid whose impact with Earth was predicted while still in space approaching Earth. Meteorite 2008TC3 and Chelyabinsk’s are part of the released data set. (Credit: NASA/SETI/P.Jenniskens)
The data from “government sensors” – meaning “early warning” satellites to monitor missile launches (from potential enemies) as well as infrasound ground monitors – shows the distribution of bolide (fireball) events. The data first shows how uniformly distributed the events are around the world. This data is now released to the public and researchers for more detailed analysis.
The newest data released by the US government shows both how frequent bolides are and also how effectively the Earth’s atmosphere protects the surface. A subset of this data had been analyzed and reported by Dr. Peter Brown from the University of Western Ontario, Canada and his team in 2013 but included only 58 events. This new data set holds 556 events.
The newly released data also shows how the Earth’s atmosphere is a superior barrier that prevents small asteroids’ penetration and impact onto the Earth’s surface. Even the 20 meter (65 ft) Chelyabinsk asteroid exploded mid-air, dissipating the power of a nuclear blast 29.7 km (18.4 miles, 97,400 feet) above the surface. Otherwise, this asteroid could have obliterated much of a modern city; Chelyabinsk was also saved due to sheer luck – the asteroid entered at a shallow angle leading to its demise; more steeply, and it would have exploded much closer to the surface. While many do explode in the upper atmosphere, a broad strewn field of small fragments often occurs. In historical times, towns and villages have reported being pelted by such sprays of stones from the sky.
NASA and JPL emphasized that investment in early detection of asteroids has increased 10 fold in the last 5 years. Researchers such as Dr. Jenniskens at the SETI Institute has developed a network of all-sky cameras that have determined the orbits of over 175,000 meteors that burned up in the atmosphere. And the B612 Foundation has been the strongest advocate of discovering of all hazardous asteroids. B612, led by former astronauts Ed Lu and Rusty Schweikert has designed a space telescope called Sentinel which would find hazardous asteroids and help safeguard Earth for centuries into the future.
Speed is everything. While Chelyabinsk had just 1/10th the mass of Nimitz-class super carrier, it traveled 1000 times faster. Its kinetic energy on account of its speed was 20 to 30 times that released by the nuclear weapons used to end the war against Japan – about 320 to 480 kilotons of TNT. Briefly, asteroids are considered to be any space rock larger than 1 meter and those smaller are called meteoroids.
Two earlier surveys can be compared to this new data. One by Eugene Shoemaker in the 1960s and another by Dr. Brown. The initial work by Shoemaker using lunar crater counts and the more recent work of Dr. Brown’s group, utilizing sensors of the Department of Defense, determined estimates of the frequency of asteroid impacts (bolide) rates versus the size of the small bodies. Those two surveys differ by a factor of ten, that is, where Shoemaker’s shows frequencies on the order of 10s or 100s years, Brown’s is on the order of 100s and 1000s of years. The most recent data, which has adjusted Brown’s earlier work is now raising the frequency of hazardous events to that of the work of Shoemaker.
The work of Dr. Brown and co-investigators led to the following graph showing the frequency of collisions with the Earth of asteroids of various sizes. This plot from a Letter to Nature by P. Brown et al. used 58 bolides from data accumulated from 1994 to 2014 from government sensors. Brown and others will improve their analysis with this more detailed dataset. The plot shows that a Chelyabinsk type event can be expected approximately every 30 years though the uncertainty is high. The new data may reduce this uncertainty. Tungunska events which could destroy a metropolitan area the size of Washington DC occur less frequently – about once a century.
The estimated cumulative flux of impactors at the Earth. The bolide impactor flux at Earth (Bolide flux 1994-2013 – black circles) based on ~20 years of global observations from US Government sensors and infrasound airwave data. Global coverage averages 80% among a total of 58 observed bolides with E > 1 kt and includes the Chelyabinsk Chelyabinsk bolide (far right black circle). This coverage correction is approximate and the bolide flux curve is likely a lower limit. The full caption is at bottom. (Credit: P. Brown, Letter to Nature, 2013, Figure 3)
Asteroids come in all sizes. Smaller asteroids are much more common, larger ones less so. A common distribution seen in nature is represented by a bell curve or “normal” distribution. Fortunately the bigger asteroids number in the hundreds while the small “city busters” count in the 100s of thousands, if not millions. And fortunately, the Earth is small in proportion to the volume of space even just the space occupied by our Solar System. Additionally, 69% of the Earth’s surface is covered by Oceans. Humans huddle on only about 10% of the surface area of the Earth. This reduces the chances of any asteroid impact effecting a populated area by a factor of ten.
Altogether the risk from asteroids is very real as the Chelyabinsk event underscored. Since the time of Tugunska impact in Siberia in 1908, the human population has quadrupled. The number of cities of over 1 million has increased from 12 to 400. Realizing how many and how frequent these asteroid impacts occur plus the growth of the human population in the last one hundred years raises the urgency for a near-Earth asteroid discovery telescope such as B612’s Sentinel which could find all hazardous objects in less than 10 years whereas ground-based observations will take 100 years or more.
The estimated cumulative flux of impactors at the Earth. The bolide impactor flux at Earth (Bolide flux 1994-2013 – black circles) based on ~20 years of global observations from US Government sensors and infrasound airwave data. Global coverage averages 80% among a total of 58 observed bolides with E > 1 kt and includes the Chelyabinsk Chelyabinsk bolide (far right black circle). This coverage correction is approximate and the bolide flux curve is likely a lower limit. The brown-coloured line represents an earlier powerlaw fit from a smaller dataset for bolides between 1 – 8 m in diameter15. Error bars represent counting statistics only. For comparison, we plot de-biased estimates of the near-Earth asteroid impact frequency based on all asteroid survey telescopic search data through mid- 2012 (green squares)8 and other earlier independently analysed telescopic datasets including NEAT discoveries (pink squares) and finally from the Spacewatch (blue squares) survey, where diameters are determined assuming an albedo of 0.1. Energy for telescopic data is computed assuming a mean bulk density of 3000 kgm-3 and average impact velocity of 20.3 kms-1. The intrinsic impact frequency for these telescopic data was found using an average probability of impact for NEAs as 2×10-9 per year for the entire population. Lunar crater counts converted to equivalent impactor flux and assuming a geometric albedo of 0.25 (grey solid line) are shown for comparison9, though we note that contamination by secondary craters and modern estimates of the NEA population which suggest lower albedos will tend to shift this curve to the right and down. Finally, we show estimated influx from global airwave measurements conducted from 1960-1974 which detected larger (5-20m) bolide impactors (upward red triangles) using an improved method for energy estimation compared to earlier interpretations of these same data.
