NORWAY - Skydiver's Close-Call With Meteor

A multiple frame picture of the meteorite falling.  Credit and copyright: Anders Helstrup, used by permission.

"Norwegian Skydiver Almost Gets Hit by Falling Meteor — and Captures it on Film" by Nancy Atkinson, Universe Today 4/3/2014

Excerpt

It sounds like a remarkable story, almost unbelievable: Anders Helstrup went skydiving nearly two years ago in Hedmark, Norway and while he didn’t realize it at the time, when he reviewed the footage taken by two cameras fixed to his helmet during the dive, he saw a rock plummet past him.  He took it to experts and they realized he had captured a meteorite falling during its “dark flight” — when it has been slowed by atmospheric braking, and has cooled and is no longer luminous.

Norwegian astrophysicist Pål Brekke confirmed to Universe Today that the story is true.  “I was part of the investigation – and kept secret for two years – in hope of finding the meteorite,” Brekke said via Twitter.

Since the search for the meteorite has come up empty so far, Helstrup’s story and video has been released in an effort to recruit more people to look for the rock.

“It has been a little hard to keep it as a secret,” Helstrup told Universe Today via email, “but everyone has been loyal to the project and helped us out!”

Helstrup has been searching with friends, family and volunteers after getting advice from experts from the Geological Museum in Oslo, Norwegian Space Centre and Norwegian meteor network, making painstaking efforts to pinpoint the location of where the meteorite fell.

“The meteorite has for sure some possible hiding spots,” Helstrup said.  “There is a forest with lots of different places it can easily disappear.  Even if there is several areas where it would be found easily, there is a river, some marshy spots and areas and lots of high grass.  Therefore the best chance of a finding would be in springtime.  But we have high hopes!”

Finding the rock would provide the definitive confirmation it really was a space rock that Helstrup captured on film.  And in fact, it is Helstrup who might be most skeptical this was a meteor.  There are experts who say there is no doubt.

“It can’t be anything else,” said geologist Hans Amundsen, quoted in the Norwegian publication NRK.  “The shape is typical of meteorites – a fresh fracture surface on one side, while the other side is rounded.”

He added that the meteorite may have been part of a larger rock that had exploded perhaps 20 kilometers above Helstrup.

What if the rock would have hit Helstrup or his diving partner?  Amundson said the rock would have cut him in half.

“Imagine a 5 kilo rock hitting you in the chest at 300 kilometers per hour,” Amundson says in the video.  “That would have led to quite an accident investigation.”

This is unique because this is the first time a meteor in dark flight has been captured on film.

“Fireballs entering the atmosphere have been filmed many times,” says Morten Bilet in the video.  Bilet is a meteorite expert.  “This is unique because it was filmed during its so called “dark flight” – after it has been burned out.  That’s never been done before so this is something new and exciting.”

SPACE - Meteor Strikes Happen 10 Times More Often

"As estimates of meteor strikes rise, how can Earth avoid destruction?" PBS Newshour 11/7/2013

Excerpt

JUDY WOODRUFF (Newshour):  It's not just in scifi movies.  Asteroids really are moving closer to Earth more frequently and chunks of them are hitting too.

The one that caught everyone's attention struck last February, when a meteor hit near the Russian city of Chelyabinsk.  It was only 60 feet wide, but injured more than 1,200 people.

New research about that meteor and other asteroids was published yesterday.  Experts say fragments are hitting 10 times more often than known before.

NewsHour science correspondent Miles O'Brien fills us in.

Miles, hello there.

So what was it about this incident in Russia that has caused scientists to believe that these rocks may be hitting Earth more often?

HUMOR - Dilbert on Meteors

Dilbert
2/21/2013

SCIENCE - Universe Just Keeps Trying to Kill Us

"The Universe Just Keeps Trying to Kill Us" by Ethan, Science Blogs 2/15/2013

Excerpt

“Don’t wake me for the end of the world unless it has very good special effects.” -Roger Zelazny

It’s always the ones you least expect that get you the worst, it seems.  I went to bed last night excited that Asteroid 2012 DA14, a 200,000 ton asteroid, was going to pass within just 28,000 km (or 17,000 miles) of Earth’s surface, which would make it the closest pass of an asteroid that large that we’ve ever observed.

Image credit:  NASA / JPL Near-Earth Object Program Office

I thought that would be the best way to celebrate today, which would be Galileo‘s 449th birthday.  After all, it was Galileo who first discovered that there was no way that Earth could be at the center of all the heavens.  By looking at Jupiter through a telescope, he discovered that it had its own set of large moons that very clearly orbited their own planet, indifferent to the workings of Earth.

We now know that these moons orbit Jupiter because of Jupiter’s gravity; this is the same reason all planets, moons and solid objects move the way they do in space.  Jupiter is the second largest gravitational source in our Solar System, behind only the Sun.  And since it’s been orbiting the Sun for over four billion years, it’s had literally hundreds of millions of passes by each object in the asteroid belt.

Every solar system has an asteroid belt, and here’s why:  as you move away from the Sun (or any star), the temperature of the interplanetary space around you drops.  Near the planet Mercury, interstellar space is somewhere around 800 °F, out by Pluto, it’s nearly -400 °F.  But there’s a critical place — out beyond Mars but before Jupiter in our Solar System — where the temperature is too cold for water to exist in any state other than frozen ice.

And once you reach that point, you’re going to get little frozen chunks of ice and rock mixed together.  So every solar system has an asteroid belt. But ours also has a large planet nearby, and over billions of years and millions of passes outside this asteroid belt, Jupiter changes the orbits of these rocky objects.

And these repeated gravitational interactions of asteroids with the other planets — primarily Jupiter — changes their orbits over time.  This is important to us here on Earth for a few reasons, but nothing makes it more apparent than seeing the havoc a collision with one of these asteroids can wreak here on our world.

This is meteor crater, from an asteroid strike about 50,000 years ago, of an asteroid that was comparable in size (maybe 50 meters in diameter) to 2012 DA14, the one that just missed us today.  Asteroids of this size — 40 meters or larger in diameter — strike Earth a couple of times every 100,000 years, and could wipe out an entire London-sized city if they struck there.

One of the big problems is that we only know of about 1% of the asteroids that are that size, so we can’t even tell when most of them are coming.  It’s only the ones that we get a good view of for a long time that we can track well enough to predict when they’re going to strike us.  The hardest ones to predict are the ones that come towards us from the direction of the Sun; we literally never see those coming.

Which is why it was such a shock when this meteor appeared in the skies over Russia early this morning!

What exactly happened here?  A much smaller asteroid than the ones we aspire to track, one only maybe 2-3 meters* in diameter, entered the Earth’s atmosphere.  Asteroids this small rate a zero on the Torino scale, as they pose no serious danger to Earth, but that doesn’t mean they can’t cause destruction.

The physics of what’s going on here is amazing.  Let’s do some Q&A about this:

• Q:  Why does it make a fireball in the sky?
  
  A:  The Solar System is a fast-moving place.  Most objects move in excess of 25,000 miles per hour relative to Earth, and you probably think the wind was problematic when you put your arm out of the window while driving down the highway!  At the astronomical speeds achieved by meteors, the outside of the meteor heats up tremendously, by many hundreds of degrees, and the fire you see is from a heat so hot that the meteor is disintegrating before your eyes.

• Q:  Why does it appear to explode in mid-path?
  
  A:  Because it really does explode!  Think about it, you’re heating this mostly frozen ice-and-rock-ball by hundreds and hundreds of degrees.  Inside the meteor, you’ve got frozen water, frozen methane, and other weird, carbon-rich molecules.  What happens when you heat these ices up?  They melt, and eventually boil.  As this boiling causes fissures in the meteor, oxygen — common in our atmosphere but rare everywhere else — can combine with these combustible gases under very high heats.
  
  And that combination of things very quickly goes boom.

• Q:  Why — like this one and the Tunguska event — do so many of these occur over Russia?
  
  A:  They don’t preferentially occur over Russia, if that’s what you’re asking.  Events like these — I call them super-bolides — occur on average about once every few years.  There was a comparable one, another 50-100 ton asteroid, that encountered our atmosphere and burned up over Indonesia in 2009; in reality, most of them occur over the ocean and so go unobserved and unrecorded.
  
  The Tunguska event was special: it’s the largest one in recorded history, and was probably just a little smaller than the asteroid that made meteor crater.  The reason these feel like they occur over Russia is simply because Russia has a huge amount of land area.

• Q:  Why didn’t we see this one coming?
  
  A:  First off, it’s small.  It’s very difficult to see something that’s just two-three meters across until you get very close to it, even with the most powerful telescopes in the world.  Even the most ambitious survey proposals of asteroids that could be potentially hazardous to Earth don’t go smaller than about ten times the volume of this one.  And second off, it came from the direction of the Sun, the hardest direction to monitor.  (Because if you’re going to build an expensive telescope, the first rule is do not fry your optics, which you’ll do if you point it too close to the Sun!)

• Q:  THIS IS A HOAX! IF IT WAS REAL WHY DIDN’T NASA PHOTOGRAPH IT FROM SPACE?
  
  A:  NASA doesn’t monitor all places on Earth all the time from space.  But this part of the world was actually monitored at the time, by the EU’s Meteosat program.

• Q:  How much damage did it cause, and how did it happen?
  
  A:  There was some localized property damage, and probably around 1,200 injured people.  When the big “flash” (or explosion) occurs, both a sonic boom and an intense pressure wave emanate from the source.  This can do things like blow out windows (imagine the damage if one hit New York City!), damage eardrums, and — in the case of Tunguska — knock even large objects completely over.  The building above had its roof collapse from the blast.
  
  But this doesn’t destroy the meteor, it just breaks it up into smaller chunks.  Many of these fragments reach the surface, still traveling at speeds that are often in excess of terminal velocity and capable of causing some pretty intense damage, similar to a cannonball strike.  The ice, below, had this giant hole created in it from a meteorite fragment.
  
  So what you hear reports of come from a combination of the initial blast wave and the secondary falling debris.

• Q:  How long before the big one strikes, and all of humanity dies?
  
  A:  Believe it or not, an event like the one that caused the mass extinction of the dinosaurs is thought to occur only every few hundred million years.  These events occur at random, which means — like getting struck by lightning — there’s no way to predict it, not with our current state of knowledge.
  
  But we could know this, what we’d have to do is find and start tracking each one of these potential Earth-killers, or any asteroid larger than a few kilometers in size.  And we could do it with our current technology, too; all we’d have to do is invest in it.

SPACE - Cosmic Coincidences

"Meteor Explosion of Atomic Bomb Strength Injures 1,000 in Russia" (Part-1) PBS Newshour 2/15/2013



"Cosmic Coincidence:  Asteroid Careens by as Meteor Delivers 'Buzz Cut' to Earth" (Part-2) PBS Newshour 2/15/2013

Excerpt

SUMMARY:  On the same day as a meteor hit Russia, an asteroid careened towards Earth.  Jeffrey Brown talks to astrophysicist Neil deGrasse Tyson about this cosmic coincidence, how the meteor and asteroid came so close to Earth, what risks it poses and why this is a 'wake-up call.'