Update on Russia’s Mega-Meteor

The asteroidal fragment that exploded over Chelyabinsk, Russia, last month delivered the kinetic-energy equivalent of at least 400 kilotons of TNT. Damage was limited because it disrupted so high up — but the situation could have been much worse.

It's been nearly a month since a big chunk of asteroid plunged into Earth's atmosphere on the morning of February 15th and put on a spectacular show in the skies over central Russia. Since then impact and meteorite specialists have raced not only to figure out where it came from but also to gather up and analyze as many fragments of the impactor as possible. From reports and interviews gathered by Sky & Telescope, they've had great success on both fronts.

First, let's recap where this interloper came from. Thanks to ample video recordings (many from the dashboard-mounted cameras of security-wary Russian drivers), it's been a snap to reconstruct the entry circumstances and, from those, the pre-impact orbit. But different teams come up with different values, as the table below reveals. (Uncertainties aren't shown; see the linked sources for those.)

Orbit of the Russian Mega-Meteor
Authors Semimajor axis Eccentricity Inclination Perihelion Aphelion
Borovicka & others 1.55 a.u. 0.50 3.6° 0.77 a.u. 2.33 a.u.
Zuluaga & Ferrin 1.73 a.u. 0.51 3.5° 0.82 a.u. 2.64 a.u.
Chodas & Chesley 1.73 a.u. 0.57 4.2° 0.75 a.u. 2.78 a.u.

The spread of values arises from how each team interprets the videos, derives the trajectory and speed as the bolide passed through the atmosphere, and then derives an orbit.

Orbit of the Cherbakul meteoroid
The orbit of the Chebarkul impactor stretched from the inner asteroid belt to near the orbit of Venus, a path the object had likely followed for many thousands of years, crossing the Earth's orbit every time on its outbound leg. Click on the image for a larger version.
Still, there's consensus that the object came from a well-populated section of the inner asteroid belt. How it got bumped inward toward Earth isn't known — yet. For example, the path's aphelion might overlap a location, 2½ a.u. from the Sun, at which there's a strong orbital resonance with Jupiter. In that case, gravitational perturbations by the giant planet could have yanked the object out of a nearly circular orbit and onto its eventual collision course with Earth.

A refined atmospheric trajectory and pre-crash orbit might eventually emerge from a team led by Peter Brown (University of Western Ontario). They're now analyzing star positions in nighttime images taken at the exact locations where several bolide videos were recorded.

Here's a "top five" list of video recordings compiled by Brown, along with the exact coordinates of the camera that took each one:

The intruder entered the atmosphere at roughly 12 miles (19 km) per second along an east-to-west track, more or less. A European weather satellite glimpsed it skirting Earth's limb (here's a reprojected view of that image). According to Juri Borovicka's team, the bolide's flight path had a slope of 16½°, and it started breaking apart relatively high up, 20 miles (32 km) above the ground.

Ground track of the Chebarkul meteoroid
The east-to-west ground track of the Chebarkul meteoroid over the last minute or so before impact. Blue numbers are the object's altitude, and an asterisk indicates the point of peak brightness, which occurred (according to NASA dynamicists) at an altitude of 14.5 miles (23.3 km).
NASA / JPL / S. Chesley
The dazzling light, brighter than the Sun, certainly got the attention of anyone looking its way — though some videos show apparently pedestrians unfazed by the bright-as-the-Sun spectacle. Purdue impact specialist H. Jay Melosh notes that what many are calling a contrail (as in "condensed water vapor") is actually a smoke trail. "Probably most of the mass ended up as fine dust that blew away," he says.

What certainly did get everyone's attention was the bolide's powerful shock wave, which reached the ground about 88 seconds later. This blast blew out countless windows in and near the city of Chelyabinsk. Although many were injured, no one was killed.

However, the damage could have been much worse. "All that blast energy was distributed over a large area," explains Mark Boslough (Sandia National Laboratories). If this half-megaton blast had been directed straight downward, he says, its fireball might have engulfed the ground. That's what happened during the 1908 Tunguska event, which involved a blast at least 10 times more powerful and much closer to the ground. But such a fate didn't befall the residents of Chelyabinsk or in the surrounding countryside, Boslough concludes. "The villages are still there."

Cherbakul meteorites
The largest known piece of the Chebarkul meteorite, weighing 4 pounds (1.8 kg) is seen here with two smaller fragments. So far hundreds of smaller pieces have been found.
Ural Federal University
Meanwhile, Russian meteorite specialists have been scrambling to collect as many pieces of the meteoritic shrapnel as they can. These fell over a wide area near the town of Chebarkul. In most cases, searchers simply looked for small holes in the ubiquitous snow cover and dug down to claim their cosmic prizes. Most of the pieces are small, no more than an inch across, and the largest fragment found to date weighs only 4 pounds (1.8 kg).

According to a team of analysts led by Viktor Grokhovsky (Ural Federal University), the fragments are a common stony meteorite type, called an ordinary chondrite, containing relatively little metallic iron. Given the power of the blast, the entry velocity, and the typical density of chondrites (about 3.6 g/cm3), Brown estimates the original object had a diameter of about 54 feet (17 m) and a mass of roughly 10,000 metric tons.

Melosh, who's studying how meteoroids break up in the much-thinner atmosphere of Mars, thinks the small-fry stones imply that the precursor object was loosely bound together, what's often termed a "rubble pile." he explains that objects slamming into the thin Martian air "break up multiple times — like a cosmic-ray cascade — so you don't get any large fragments."

Magnetic map of Lake Cherbakul
A map of the magnetic field measured at the bottom of Lake Chebarkul. The area shown measures 100 by 60 meters. Red areas might indicate the location of large fragments of the Chebarkul meteorite, which fell in countless pieces across the region on February 15, 2013.
Ural Federal University
But what about that big, mysterious 50-foot (16-m) hole created in the ice covering Lake Chebarkul? Grokhovsky believes it was created when a large chunk of meteorite, 2 feet (60 cm) long and weighing roughly 200 pounds (100 kg) fell into the lake. That's what divers expected to find lying on the lake bottom, about 35 feet (10 m) down, but after exploring the murky, silty conditions they came up empty-handed.

However, earlier today researcher Evgeny Narkhov (also at Ural Federal University), released a preliminary map of magnetometer readings taken over an area the size of a football field. The lakebed map shows several hot spots, suggesting that the meteorite likely broke apart on impact. "There are not small pieces and a large one, as you might think, but several large fragments," Narkhov notes in a university news statement. Analysis is continuing, but I'm guessing the divers will be heading back down very soon.

Meanwhile, after ignoring some initial offers that were clearly fraudulent, meteorite collectors report that genuine bits of the Chebarkul fall are finally making their way into the marketplace. The going rate is $30 to $40 per gram. But nationalistic pride and protectionism are involved, and the Russian Duma is considering a proposal to prohibit the exporting of meteorites — a practice that is permitted for now.

13 thoughts on “Update on Russia’s Mega-Meteor

  1. John Sheff

    Kelly, I’m confused about something: Was the damage caused by a sonic boom as the object entered the atmosphere moving faster than sound, or was the damage caused by the explosion of the object at the end of its trajectory?
    – John Sheff

  2. Grassychops

    "One minute and 28 seconds later, shock waves from its deceleration and explosion collapsed walls and blew out roughly 100,000 square meters (1 million square feet) of windows."

  3. Peter WilsonPeter

    John: The sonic boom and the shockwave from the explosion add together. Guess the moral of the story is that if you see an extremely bright light outside in the sky, turn away from the windows, not towards them.

  4. Eric Holcomb

    As I understand it, the meteor "explosion" can be thought of as a greatly intensified sonic boom resulting from the large increase in surface area and drag when an object travelling at hypersonic speed breaks apart. There is no chemical or nuclear release of energy, but the kinetic energy involved is enormous. Without the mid-air breakup, the energy would be released much more slowly (with much less "boom") … until impacting the ground.

  5. Anthony BarreiroAnthony Barreiro

    Thanks Kelly. It’s very cool that we’re able to understand so much about this meteor, from its original orbit in the asteroid belt all the way to its steaming entry into a frozen lake.

  6. Krzysztof Wlodarczyk

    I would like to present the results of my computations:
    a=1.55AU, i=6.8 deg, e=0.6, q=0.63, Q=2.47. I is quite unusual that the nodes of this orbit roughly correspond to those of 2012 DA14 ! In addition, I have a light curve in V and R. The visual brightness at Chelyabinsk center reached -33.8 magnitude, thus 700x brighter than the Sun ! I would like to present the light curve, so please send me an e-mail address to send it.

  7. Babu G. Ranganathan

    ASTEROIDS, COMETS, AND METEORS ORIGINATED FROM EARTH: In the Earth’s past there were powerful volcanic explosions propelling millions of tons of earth soil and rock (now asteroids and meteors) containing organic molecules. Read my popular Internet article, ANY LIFE ON MARS CAME FROM EARTH. The article explains how millions of tons of Earth soil may exist on Mars, and how debris we call asteroids and meteors could have originated from Earth. According to a Newsweek article of September 21, 1998, p. 12 that quotes a NASA scientist, SEVEN MILLION tons of Earth soil may exist on Mars! How could this be possible? Read and find out.

    Even if the right chemicals exist, life cannot arise by chance. The molecules that make-up life have to be in a sequence, just like the letters found in a sentence. Please read my popular Internet articles listed below:

    Check out my most recent Internet articles and sites: THE SCIENCE SUPPORTING CREATION and WAR AMONG EVOLUTIONISTS (2nd Edition)

    Babu G. Ranganathan*
    B.A. Bible/Biology

    *I have given successful lectures (with question and answer period afterwards) defending creation before evolutionist science faculty and students at various colleges and universities. I’ve been privileged to be recognized in the 24th edition of Marquis "Who’s Who in The East" for my writings on religion and science

  8. Bruce

    Mr. Ranganathan, while I find some of your comment and writings to be interesting, the opening statement in your post is most implausible. While it is conceivable that some meteoric material is returning fragments that where once blasted off earth (either by super volcanoes as you suggest or by great impacts from large asteroids or comets), your opening assertion seems to be that all or most “asteroids, comets, and meteors originated from earth.” Are you contending that the asteroid belt between Mars and Jupiter came from Earth? Comets are observed coming in from the outermost reaches of the solar system. To claim that asteroids and comets came from earth causes you to undermine your credibility. It pains me to point this out, since other writings of yours that you mentioned are very well reasoned, and I hope that others will read them and judge them for themselves. A scriptural principle that comes to mind is Phil. 4:5. Please know that I mean no offense. Sincerely, mayfield.bruce@ymail.com

  9. Krzysztof Wlodarczyk

    I would like to present the light curve in V derived from video taken in Kamensk Uralsky. The visual magnitude at maximum air burst was "only" -24.5 in Kamensk, -27.5 in Chelyabinsk and -28.5 mag in Korkino.

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