Tag Archives: impact

Bizarre green meteorite NWA 7325 may be from Mercury

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Wow, that’s what I call green! Green, glassy fusion crust coats one side of Ralew’s new meteorite. This is the largest of the 35 fragments, weighing just over 100g. Cube at right is 1 cm across. Click for larger version. Credit: Stefan Ralew

In April 2012 Stefan Ralew, a meteorite collector from Berlin, found himself staring at a spread of 35 green meteorite fragments for sale by a dealer in Morocco

“It was offered as a Martian (meteorite) but for me it was simply far too green,” said Ralew. Moroccan meteorite always keep an eye out for green rocks in the belief that they’re of Martian origin. Sometimes however they turn out to be nothing more than Earth rocks. Since this one was expensive, Ralew would have normally declined, but he noticed that the pieces had fusion crust, that frothy, typically dark coating of melted rock that forms when a meteorite is heated during its fall through the atmosphere.

Stefan Ralew Credit: Mirko Graul

“It was a big risk because of the high price,” said Ralew, but he sealed the deal and mailed off a piece to Dr. Tony Irving at the University of Washington, well-known for his expertise in meteorites from other planets.

After chemical analysis, Irving discovered that Ralew’s green rock was a completely new type of achrondrite (ay-KON-drite), a class of igneous meteorite that forms deep within the crust of larger asteroids and planet-sized bodies. In fact, Ralew’s green meteorite shared similarities with the planet Mercury, making it a one-of-a-kind.

Many of the more familiar achondrites that scientists and meteorite hunters have picked up here on Earth were blasted from the surface of Vesta by meteorite and asteroid impacts. Still others have been liberated from the moon and Mars. They drift through space until swept up by the ceaseless Earth. Scientists have done the math and arrived at the conclusion that meteorites from Mercury impacts should also by lying around in the deserts of the world, preserved by arid air and lack of rain. But no one had definitely identified a rock from Mercury until the green meteorite entered the scene.

A closeup of a polished, cut face of NWA 7325 shows striking green crystals of chromium diopside (a silicate mineral with chromium) and gray crystals of plagioclase, a rock also common in Earth’s crust. Click for larger version. There are a total of 345 grams (about 12 ounces) mostly in small fragments. Credit: Stephan Ralew

Other classes of achondrites called aubrites and angrites were once believed to have originated on the innermost planet, but further research points to their home on a yet-unknown asteroid or planet.

Mercury photographed by MESSENGER. The planet’s crust lacks iron and is pockmarked by countless craters. One of these impacts possibly sent NWA 7325 our way. Credit: NASA

Stefan’s meteorite, now classified as NWA 7325 (NWA=Northwest Africa, its find location), is a near-match for rocks examined from orbit by Mercury MESSENGER space probe. NWA 7325 is rich in magnesium, calcium and a silicate material laced with chromium that lends it an emerald sparkle, but it lacks iron. And that’s the key. Surface rocks on Mercury are likewise igneous and depleted in iron.

The match isn’t perfect. NWA 7325 has more calcium than it should and lacks the silicate mineral enstatite (common on Mercury), but that doesn’t worry scientists too much. Because the rock was excavated from deeper down in the crust, it would be expected to have its own unique qualities.

Mars meteorites show evidence of shock from impact in their crystal structures, and the same would be expected for rocks delivered to us from Mercury. Plagioclase, a very common mineral in Earth’s crust, and found in abundance in NWA 7325, has been completely melted, likely due to shock from the impact that sent it flying from the planet long ago.

Bubbly fusion crust on another fragment of Stefan’s meteorite. Click for larger version. Credit: Stefan Ralew

While the evidence points to a Mercury origin, we won’t really know for certain whether Ralew’s rock originated from the innermost planet until further studies are done. Scientists are still working to determinewhen those gorgeous green crystals formed as well as how long the rock coasted through space before arriving on Earth.

“Ultimately, only a sample return from Mercury may provide an answer,” wrote Irving in his group’s recent report on NWA 7325. In the meantime, Stefan’s meteorite stands as one of the most singular finds to date. It couldn’t have happened to a better guy. Ralew has a been a great friend of meteorite collectors and the scientific community for years. You can check out his website HERE.

New asteroid book good medicine for the doomsday blues

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Don Yeoman’s new book on asteroids is a great read. Photo: Bob King

I just finished reading Donald Yeomans’ excellent new book “Earth-Approaching Asteroids: Finding Them Before They Find Us” and figured many of you might enjoy hearing about it. The book is published by Princeton University Press and available from Amazon for $15.73.

Author Donald Yeomans might be known to some of you already for his youtube video debunking 2012 doomsday predictions.  He works as a senior research scientist at the Jet Propulsion Lab, where he manages NASA’s Near-Earth Object Program Office. His book offers an excellent introduction to the layperson on near-Earth asteroids (NEAs), those objects that can potentially pass within about 29 million miles of Earth as they orbit around the sun.

Yeomans’ primary focus is on a smaller group within the NEAs called the PHAs or potentially hazardous asteroids. These pass within 4.65 million miles of the planet and span at least 500 feet across, large enough to cause significant destruction should they impact Earth. Close-approaching comets are also discussed.

The book is 161 pages long and divided into 10 chapters, starting with asteroid and comet basics and moving on to how astronomers calculate orbits and name names. Next is an overview of the new Nice model (developed in Nice, France) of the solar system’s evolution, where we learn that the giant planets did not form where they now reside.

Author Donald Yeomans

Gravitational interactions of Jupiter, Saturn, Uranus and Neptune with each other and the small asteroid-like building blocks of the solar system called planetesimals caused the outer planets to migrate over time. As they moved to their current locations, they scattered planetesimals hither and yon to form the current main asteroid belt between Mars and Jupiter and the distant Kuiper Belt beyond Neptune. It’s a fascinating read and goes far in explaining the present-day layout of the solar system.

With the Nice model as background, Yeomans delves into how asteroids from the main belt – the origin of nearly all NEAs – are delivered into Earth-crossing orbits through a combination of the Yarkovsky effect and gravitational nudges from Jupiter and Saturn. Heat absorbed by a rotating asteroid from the sun radiates back into space, giving it a little push and causing the asteroid to spiral toward or away from the sun – this is the Yarkovsky effect. Once the asteroid crosses into a “resonance” point with Jupiter or Saturn, it can then get tossed into the near-Earth neighborhood.

Because near-Earth objects, both comets and asteroids, are composed of primitive materials from early days of the solar system’s history, Yeomans believes they’re critical to understanding our origins. These small bodies may well have delivered much of the water and organic (carbon-containing) compounds necessarily for life to have evolved on Earth.

Plot showing the rapid increase in near-Earth asteroid (NEA) discoveries beginning in the late 1990s due to the increase in telescopic surveys and use of CCD technology. Credit: Alan Chamberlain, NASA-JPL/Caltech

The first near-Earth asteroid, 433 Eros, was discovered in 1898, while the first dedicated survey to hunt for them didn’t begin until 1973, when Gene Shoemaker and Eleanor Helin used the 18-inch Schmidt telescope on Mt. Palomar to search for small, fast-moving asteroids.

Yeomans describes accelerating efforts to find and track NEAs in the 1980s and 1990s thanks to workshops and papers by asteroid researchers, the discovery of the dinosaur extinction-asteroid connection and introduction of CCD technology (electronic cameras) that allowed for much more rapid and efficient surveys.

As scientists and legislators realized the potential destruction power of near-Earth objects, part of NASA’s budget was directed toward creating the Near-Earth Objects Observations Program in 1998. Its goal: to detect, track and characterize 90 percent of near-Earth asteroids 1 km and larger. The lower limit for an asteroid or comet to cause a global disaster is 0.9 miles (1.5 km).

Especially interesting is how the notification system works should a potential threat be detected during a survey run. I’ll leave it for you to read, but let’s just say, there are many checks before an announcement would be made.

Table from the book showing average asteroid impact results by size. Credit: Don Yeomans

Yeomans describes asteroids’ and comets’ compositions and how we might mine near-Earth asteroids for materials to build space ports and rockets. Much of our planet’s metal content long ago sank to the core or is otherwise deep beneath the surface. Asteroids wear their metals on their sleeves so to speak, with abundant iron, nickel and precious metals like platinum and rhodium much more easily available.

Later chapters go into detail about the potential threats of near-Earth objects, how orbits are refined through continued observation and the protocols in place should an alert need to be issued. Already about 90 percent of NEAs 0.9 mile and larger have been discovered; no known asteroids of this size will impact Earth for at least the next 100 years.

The final chapter describes what we’d do to deflect a potentially threatening asteroid. The slow-pull gravity tractor method (changing its trajectory by “towing” into a safer orbit via gravity from a neighboring spacecraft) and detonating a nuclear device on or near an asteroid are explored.

I highly recommend the book. Since it covers so many aspects of these fascinating asteroids, I found it comprehensive and a great read. While Yeoman covers a topic that some of us worry about, he provides the facts needed to stay cool yet informed. One very small criticism – a list of web resources on the topic in the index would have been nice addition.

I liked the occasional touches of humor, such as when the author wondered why there wasn’t a “rhodium” credit card yet, since that metal’s even more precious than the vaunted “platinum”. We’ll finish with the book’s final sentence:

“Near-Earth objects are among the smallest members of the solar system, but their diminutive size is in no way proportional to their importance. When it comes to their role in the development and future of humankind, next to the sun itself, theirs is the most important realm.”

Meteor likely cause of Jupiter flash; Saturn’s B-ring gets scrambled

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Jupiter on September 11 through a 12-inch telescope. The Great Red Spot is visible plus a smaller red spot nearby. The little bump at bottom left is the moon Ganymede. Credit: James Willinghan

Still no sign of an impact in Jupiter’s cloud belts by amateur and professional astronomers. I’ve looked at lots of pictures of the planet since Monday and while there are plenty of odd-looking swirls and patches in the clouds, but nothing like the spots that appeared in 2004 and 2009. Odd is the norm when it comes to the solar system’s biggest planet. Jupiter’s ever changing cloudscapes defy the imagination in their weird variety, making it the most rewarding to follow in a telescope. The weather and cloud patterns change constantly much like they do on Earth.

The flash location has been corrected to longitude 345 degrees (System I) and +2 degrees north, putting it squarely within the white Equatorial Zone we talked about yesterday. Based on its brightness and lack of a dark scar, Dr. Michael Wong, assistant researcher University of California astronomy department, concluded that the object that struck Jupiter was too small to singe the cloudtops.

Dramatic dark clouds from the impact of fragments of Comet Shoemaker-Levy 9 were visible even in small telescopes in July 1994. Credit: NASA/ESA

The impacting meteoroid is estimated to have been under 33 feet (10 meters) across. Had an object this size hit Earth’s atmosphere, it would have flared at least as bright as the sun and perhaps sprinkled meteorites along its path.

Unfortunately it appears the space rock that hit Jupiter didn’t have the energy to affect the chemistry of its atmosphere enough to leave a visible trace. In this regard, it resembles the previous two impacts in 2010.

Jupiter’s a big planet with a lot of gravitational pull. Meteors must routinely come crashing in and burn up in its atmosphere. We almost certainly miss most of them just as we do on Earth when bright meteors flash across vast, remote locales like the central Pacific and Canadian Arctic.

Still, not much gets by Earth’s army of amateur astronomers who love the sky and spend countless hours watching and recording it. To date, there have been five confirmed instances of meteoroids/comets bashing Jupiter. The first one was predicted to happen after astronomers discovered that a busted comet would rain down on the planet in July 1994. All the remaining events were discovered by amateurs.

The inner edge of the B-ring (left) shows a clumpy texture from ring particles – mostly ice – bunched together by the gravitational tugs of the moon Mimas. The photo was taken on July 10, 2009 from 198,000 miles away. Credit: NASA/JPL/SSI

NASA released a wonderful picture this week of the outer edge of Saturn’s clumpy B-ring taken by the Cassini orbiter. The other rings appear smooth because the chunks of ice they’re composed of are too small be resolved by the camera. That’s where the moon Mimas comes into play. Mimas (ME-muss or MY-muss) orbits Saturn once for every two orbits the icy particles in the B-ring complete. Regular, repeated nudges by the moon’s gravity are thought to give the ring its sharp edge as well as compress the particles into visible clumps.

Pure speculation on my part, but I wonder if Mimas might create tiny temporary moonlets through its interaction with the B-ring. Could a clump get big enough to gather into an evanescent moonlet before Saturn’s gravity gains the upper hand and disassembles it?

Wide view of Mimas and Saturn taken by Cassini. The B-ring is Saturn’s largest and brightest ring. It’s separated by the outer A ring by a dark gap called Cassini’s Division. Mimas is responsible for removing much of the ring material in the gap. Credit: NASA

Jupiter impact and video update; the moon and Venus show off at dawn

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Flash from a possible impact on Jupiter about 6:30 a.m. (CDT) Monday morning Sept. 10. Frame from video clip. Credit: George Hall

I just had to get up for a look. Any dark spot on Jupiter from Monday’s potential impact was straight up in view at 4:15 a.m. Before the neighborhood rooster crowed, I had the 10-inch reflector pointed at Jupiter. The air was fluttery and unsteady but there were occasional moments when the planet sharpened up for a clear view at 212x. Nothing obvious was visible, nor has there been a “spot sighting” by other observers either visually through a telescope or by camera. That doesn’t mean an impact didn’t happen; maybe the scar hasn’t grown big enough to see yet.

The white circle shows the approximate location of the where the flash was observed early Monday morning. This photo was taken this morning September 11 and shows no evidence of an impact. Credit: Wayne Jaeschke

George Hall’s 4-second video clip shows a clear rise to peak brightness followed by a quick fade. It really does look like Jupiter got hit. One thing you’ll notice is that the flash happens further south of the dark North Equatorial Belt in broad, pale zone astronomers call the Equatorial Zone (EZ). My guess is that the position of the possible impact will be revised.

There will be lots of eyes and telescopes pointed at the planet in the coming days and weeks. Hopefully we’ll know one way or another soon. Below is a short list of times (CDT) when the “impact zone” will be face on and most easily viewed in a telescope. The times are Universal Time, so remember to subtract 5 hours for Central Daylight time, 4 for Eastern, 6 for Mountain and 7 for Pacific:

Sept.11 –  19:00
Sept.12 — 04:51
Sept.12 — 14:41
Sept.13 — 00:32
Sept.13 — 10:22
Sept.13 — 20:13
Sept.14 — 06:03

Look to the east tomorrow (Sept. 12) at dawn to see the two brightest nighttime sky objects right next door to each other. Created with Stellarium

OK, so Jupiter’s pretty cool right now. Let’s not forget there’s a nice conjunction of the crescent moon and Venus tomorrow morning at dawn. The two won’t approach the snugness of the Jupiter-moon pairing a few days ago but will still be a beautiful sight before sunrise. They’ll be about 4 degrees apart for Midwestern viewers. Closest approach happens in daylight for the U.S. at 10 a.m. (CDT). Venus will then be 3.6 degrees due north of the crescent.

Venus, a very overexposed crescent moon, Jupiter and Orion around 5 a.m. this morning September 11. Photo: Bob King

Once again, if you can spot the moon high in the southern sky around that time, binoculars will easily show Venus. Through a small telescope Venus looks like a miniature version of the last quarter moon.

Possible bright impact seen on Jupiter

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Bright flash of a potential comet or asteroid striking Jupiter’s atmosphere earlier this morning (Sept. 10). This is single frame from a video made with a webcam by amateur astronomer George Hall. Credit: George Hall

Stop the presses! Word comes this evening of a possible new impact on Jupiter observed by amateur astronomer Dan Peterson of Racine, Wis. He saw “a bright white two second long explosion just inside Jupiter’s eastern limb” at 11:25:30 Universal Time (6:25 a.m. CDT) on September 10. Peterson was using a 12″ telescope at a magnification of 400x. The brief flash was located inside the southern edge of Jupiter’s North Equatorial Belt (NEB).

In an amazing bit of serendipity, George Hall, an amateur astronomer from Dallas, Texas, was also observing Jupiter at the same time and recorded a bright flash with a webcam mounted on his 12″ telescope at about 6:30 a.m. CDT.

The dark spot at the top of Jupiter appeared in the wake of an impact by a small asteroid into the planet’s clouds. It was first seen by Australian amateur astronomer Anthony Wesley on July 19, 2009. Credit: Anthony Wesley

If the impact is real, we should see a dark “sooty” cloud develop in the aftermath of the burnup/explosion similar to dark spots that developed after earlier hits by Comet Shoemaker-Levy 9 in 1994 and smaller ones in 2009 and 2010.

Amateurs who’d like to confirm these observations are urged to look at Jupiter at the earliest opportunity. The impact location is at System I longitude 335 degrees, latitude +12 degrees north. You can download Meridian to help you find out when that location is best visible from your time zone.

South is up and east to the right as you’d see the planet in a typical astronomical telescope. Credit: Claude Duplessis’ Meridian software

You can also use this frame grab from Meridian (left) with the approximate location of the flash shown by the white box. The possible impact zone will face observers tomorrow morning around 4 a.m. CDT (5 a.m. EDT, 2 a.m. PDT) when Jupiter is well placed for viewing high in the eastern sky.

GRS in the illustration stands for Great Red Spot, which is currently very pale pink.

Shocking news about Earth’s 182 craters

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Meteor Crater, also known as Barringer Crater, was excavated by an iron meteorite 54 yards wide 50,000 years ago. It's 3/4 mile in diameter and 570 feet deep. Credit: NASA

Yesterday we touched on Mars and moon craters. Earth also had the pleasure of meteorite and asteroid pummeling over its 4.6 billion-year history. While it’s easy to spot craters on the moon with little more than 10x binoculars, finding them on our planet takes scientific sleuthing. Most have long since been erased by water and wind erosion, glaciers, volcanoes and the ever-changing jigsaw puzzle of our planet’s crustal wanderings known as plate tectonics.

Can you spot the crater? The Sudbury Basin in Ontario, Canada is the large, tilted oval across the center of the picture. It's 39 miles long x 19 miles wide. Sudbury, the second largest crater on Earth, formed during an impact 1.85 billion years ago . Originally round, its shape has been distorted by geological processes. A second crater called Wanapitei (upper right) formed 37 million years and is now a lake. Credit: NASA

To date 182 confirmed craters or impact structures have been discovered on terra firma. Most blend into the landscape and wouldn’t be known if it weren’t for telltale shock features found in local rocks. Others, like Meteor Crater near Flagstaff, Arizona, stick out like a sore thumb.  In only a small minority have fragments of the impactor been found around the craters – Meteor Crater, Kamil (Egypt), Henbury (Australia), Sikhote-Alin (Russia), Wabar (Saudi Arabia) and Campo del Cielo (Argentina) to name a few.

Iron-nickel fragment from Meteor Crater. The metal crystal pattern is peculiar to iron meteorites and not found in earthly iron. Photo: Bob King

The pieces are almost always iron-nickel meteorites. Though much rarer than stony meteorites, irons are more resistant to weathering than rocky meteorites and more likely to survive passage through the atmosphere intact.

Without meteorites as clues, how do scientists know whether a suspected Earth crater has an extraterrestrial origin? This or that hole or depression might just as well be an ancient lake bottom or sculpted by a volcanic explosion.

No meteorites were found at the Tenoumer crater in Mauritania in Africa but shocked rocks and frothy impact melt glass like the 4-inch wide slice (inset) clinched its extraterrestrial origin. Click photo to learn more. Credit: NASA and Bob King (inset)

The key discovery was made by geologist Eugene Shoemaker in 1960 when he uncovered strongly shocked forms of quartz called coesite (KOH-site) and stishovite in sand and rocks in Meteor Crater in Arizona.

The 1.1 mile diameter Lonar Crater in India is filled with a saltwater lake. Shocked quartz as well as impact breccia mixed with glass (inset) were found within the crater's rocks. Lonar formed between 35,000 and 50,000 years ago. Click photo to learn more. Credit: Wiki and Bob King (inset)

Under the extreme pressures and temperatures experienced during a large meteorite impact, quartz is transformed into these new minerals. No volcano nor any other force on the surface of the Earth, except the detonation of a nuclear bomb, has the power to alter quartz in this way.

Sand-sized quartz grain from the Chesapeake Bay impact structure showing two sets of shock lines at angles to one another. Credit: U.S. Geological Survey

Scientists could now use shocked quartz as a litmus test to identify impact craters. And since the mineral abounds on Earth, all they need to do is gather pieces from a suspected impact crater and bring them back to the lab. There they examine the specimen under a powerful microscope for tiny crystals of coesite and stishovite.

Meteoric impact also leaves behind “tracks” as multiple sets of shock veins within quartz crystals (above).

Space station astronauts and surveillance satellites find occasional new craters from orbit that are later confirmed by ground expeditions. Even regular folks have spotted potential impacts from the comfort of their homes and offices using Google Earth.  The recent Kamil crater in Egypt was discovered in satellite imagery by a former museum curator in 2008. An expedition to the remote hole in 2009 turned up 1.6 metric tons of iron meteorite fragments!

Beautiful shattered rock called breccia in specimens from Lake Wanapitei (left) and Gardnos Crater in Norway. Click to learn more. Photo: Bob King

Along with shocked quartz, meteorite impacts blast, tumble and mix local rocks into a tutti-frutti of fragments that are compacted over time into breccias (breh-chuhs) . The heat and pressure of a strike also melts rocks, forging curious varieties of glass called impact melts.

Breccias and impact-made glasses are known collectively as impactites. Some impactites even contain bits of the original impactor. While not as exotic as meteorites, these altered rocks represent Earth’s inaction with meteorites and are fascinating materials in their own right.

Year 2000 map of Earth impact craters. Several of the featured craters are shown. Click to visit the Earth Impact Database.

Tomorrow we’ll look at another type of impact debris on Earth – the enigmatic tektites.

Amateur astronomers record probable lunar impact

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The northern lights put on a great show south of Tromsø, Norway last week. Details: Canon 5D Mark II, 14 mm lens at f/2.8, ISO 2500 and 2-second exposure. Credit: Ole Salomonsen

While observers in the northern U.S.  and southern Canada have seen little to no northern lights in the wake of recent solar flares, that hasn’t been true for people living in the Arctic north. This photo is proof of that. It was taken on Valentine’s Day near Tromsø, Norway, the aurora capital of the world. Although the moon was out at the time (upper left), it did little to compromise such a beautiful picture. In fact, the sparkle it added to the snow in the foreground gives us a feeling of really being there. Click HERE to see more of Ole’s aurora photos.

A likely meteorite hitting the moon caught on video on February 11. Credit: Stefano Sposetti

Last week the online lunar studies magazine Selenology Today reported that two European amateur astronomers simultaneously detected a probable meteor impact on the moon on February 11. Stefano Sposetti and Marco Iten, both of southern Switzerland, were monitoring the earth-lit portion of the crescent moon through their telescopes. Each captured the sudden flash along the moon’s dark limb on video around 9:37 p.m. local time.

No word in how large an object created the flash, but judging from its brightness, it must have been at least a few inches across. In other words, a nice-sized rock.

The small spot at left shows the location of the observed impact along the extreme western edge of the moon. Credit: courtesy Selenology Today

We’re used to hearing about the occasional meteorite landing on Earth, but don’t often consider the same happens on the moon.

Most meteors burn up as they’re seared by our atmosphere. If not, the air reduces a meteor’s speed from around 50,000 mph to no more than that of a rock tossed off a tall building. It lands with a hard smack, but unless a meteorite is substantial, most don’t make craters and only monster ones vaporize on impact.

The moon is different. Even though it’s smaller and has less gravity to pull on incoming space rocks, it lacks an atmosphere to slow them down. Meteorites hit the moon’s surface at their original cosmic velocities of dozens of miles per second. Many vaporize on impact – the flash you see in the video – and gouge surprisingly large craters for their size. Even a rock as small as five inches across can make a crater 10 feet in diameter. The meteorite’s energy comes from its speed, which converts it into a powerful, rock-excavating machine on impact.

The first meteor seen to strike the moon was in 1999. A handful of others have been recorded since.  Scientists are very interested in how often meteorites strike the moon because if we ever send astronauts back there to build a permanent base, we’ll have to consider where and how to build to safely avert the occasional meteorite. My suggestion: underground.

Prettiest sight in the universe

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A summer of sun and rain makes for a bountiful tomato harvest. Photo: Bob King

I’ve seen a few pretty sights in this universe but few compare to the tub of tomatoes I took out of my garden yesterday afternoon. Man, look at those shiny beauties, each an edible red dwarf of the first magnitude.

Now that a second impact has been seen on Jupiter within a span of less than three months, amateur and professional astronomers are considering ways to keep the planet under 24/7 surveillance to find out how common these events really are. To do it, you’d have to coordinate efforts among astronomers spread across the globe. Since amateurs are passionate about such things and have more time than professionals to devote to a project like this, the time is right.

You’d need a moderate-sized telescope and video camera dedicated to taping the planet when it’s well-placed in the sky from your location. If several amateurs spaced every 4 time zones or so across the planet were involved, Jupiter could be watched 24 hours a day. Assuming three observers per region – in case of clouds at one location or another – the job could be handled by a couple dozen very dedicated people. Remember, even though a telescope can track a planet automatically through the night, someone still has to look through the data. We’re talking a lot of work. Perhaps a computer whiz could write software to ferret out only those images containing point-like flashes.

Since 1994, Jupiter's been hit four times that we know of by solar system debris. Clockwise from upper left: Fragments of Comet Shoemaker-Levy 9 created these dark clouds in the planet's atmosphere in July 1994; the dark impact spot discovered July 2009; the bright flash of impact on June 3 this year and another fireball from this weekend's event. Credit: NASA/ESA (upper left), Anthony Wesley (upper right and lower left) and Masayuki Tachikawa

Whether that happens or not, small asteroids and comets are smacking the planet more often than anyone ever thought. Being the largest planet in the solar system with the greatest surface area and strongest gravitational pull, we shouldn’t be surprised at its dust-buster prowess. As far as my own observing is concerned, I’ll be training my eye and keeping watch in anticipation of seeing one of these fireballs for myself one evening.

Look for Vega due south near the zenith at the same time its skymate Arcturus shines in the west. Can you see the color difference between the two? This map shows the sky at 10 p.m. in late August. Created with Stellarium

Last night I was out at 10 and immediately noticed that Arcturus, the 4th brightest star in the sky, was due west and twinkling in a frenzy. At the same time, the sky’s 5th brightest star, Vega, was due south near the top of the sky. Because of its greater altitude, Vega’s light was less troubled by the more turbulent, denser air at lower elevations and so twinkled less. Take a look for yourself and compare. Arcturus stood 40 degrees or “four fists” above the horizon. The lower we direct our gaze, the more our line of sight passes through the lower or denser part of the atmosphere where additional air layers and winds shove a star’s light about. The lower atmosphere also contains more water vapor and particulates which combine to dim a star’s light as it approaches the horizon.

Tonight the moon will be nearly as full as tomorrow night, the calendar date of full moon. That’s because the moment of full moon is 12:05 p.m. Central time Tuesday. Look at the moon tonight at 10 and you’re seeing it 14 hours before full; tomorrow night at 10, you’re seeing it 10 hours after full. Before full moon, there’s a slight bit of shading along the moon’s eastern (left) edge. After full, the eastern side is fully illuminated by sunlight but now the western (right) edge starts to show a five o’clock shadow. The difference in shading is very apparent in a telescope, but can you see this subtlety in your binoculars? Give a look and let us know.

The shadow will expand over the coming nights to consume the moon by degrees until nothing’s left but a crescent at dawn. The moon is ever on the move as it orbits the Earth, changing its angle between us and the sun and waxing and waning in phase over the course of a month.

News flash – Another Jupiter fireball!

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A frame from Tachikawa's video with an arrow pointing to the flash.The Great Red Spot is at top. Credit: Masayuki Tachikawa

Japanese amateur astronomer Masayuki Tachikawa, 52,  of Japan, captured video of a possible new impact on Jupiter at 3:32 a.m. local time (1:32 p.m. CDT) August 21. The small, 2-second duration brightening near the north edge of Jupiter’s Northern Equatorial Belt (rough position is 140 degrees System II, +17)  looks very similar to another flash seen by Jupiter observers Anthony Wesley and Christopher Go back on June 3. That spot was likely caused by the impact of a small comet or meteoroid in the planet’s atmosphere.  Tachikawa’s flash was later confirmed by Tokyo amateur Aoki Kazuo whose photo you can see HERE.

The two observers were separated by hundreds of miles and recorded the impact at the same time and location on the planet, ruling out any chance it might have been a glitch in a particular camera or glint from a satellite. Observers have been on the lookout for impact-related debris during later rotations of Jupiter but have yet to see anything.

To watch a video of the event, please click HERE. More information can be found on Kelly Beatty’s blog at Sky and Telescope’s website.