By Sergei L. Loiko This post has been corrected and updated. See link below for details.
October 17, 2013, 8:54 a.m.
ST. PETERSBURG, Russia — Ukrainian astronomers say an asteroid might collide with Earth in a couple of decades, a Russian news service reported Thursday.
Space watchers from the observatory in the Crimean peninsula said they discovered an asteroid about 1,345 feet in diameter, which they call 2013 TV135, that is approaching Earth at a potentially dangerous trajectory, RIA Novosti said.
The astronomers calculated the date of a potential collision as Aug. 26, 2032, the news service said, but they acknowledged the odds of an impact as 1 in 63,000.
The force of such a possible collision could be the equivalent of setting off about 2,500 megatons of TNT, RIA Novosti reported.
The first comet discovered this year, Comet C/2013 A1, is currently projected to pass within about 23,000 miles (37,000 km) of the surface of Mars late in 2014. While this event in itself promises spectacular views for astronomers, the uncertainty of the comet’s orbit includes a significant chance of an impact on Mars. If this happens, the impact would be hundreds of times more powerful than the asteroid impact that wiped out the dinosaurs on Earth.
C/2013 A1 was discovered on January 3, 2013, by experienced comet hunter Robert McNaught, who has discovered 74 comets and 467 asteroids. The discovery was made using a 0.5 m (20-inch) Schmidt telescope at Siding Spring Observatory in New South Wales, Australia. After his discovery, astrographs showing the comet on December 8 were found from the Catalina Sky Survey, and used to help establish the orbit.
At discovery, the new comet was well beyond the orbit of Jupiter. It is approaching the inner solar system from south of the ecliptic on a hyperbolic orbit, and is presently moving sunward at about 35 km/s (22 m/s). Based on its brightness and distance, the size of the new comet is estimated at roughly 20-40 kilometers (12.5-25 miles). For comparison, asteroid DA14, which recently passed within 27,700 km (17,200 miles) of Earth’s surface, was only about 30 m (100 ft) in diameter.
What is not typical is that, based on the latest observations, the new comet’s orbit passes Mars on October 19, 2014 at a distance of less than 37,000 km (23,200 miles). The comet’s velocity relative to Mars at that point will be about 56 km/s (35 m/s). The uncertainty in the orbit indicates a collision with Mars is possible.
This would not be a minor collision. Rather, it would be a once in a billion years collision, generating a crater roughly 500 km (300 mi) in diameter. The equivalent explosive force would be in the range of five to twenty billion megatons of TNT. I’m not sure that any number can really let us understand the magnitude of the collision – does half a trillion Hiroshima bombs convey a more comprehensible image? Another comparison is that the impact is about equal to a tenth of a second of the Sun’s total energy output focused on one spot on the Martian surface. Not a pleasant experience for any planet.
The first firm details of the 15 February asteroid impact in Russia, the largest in more than a century, are becoming clear. ESA is carefully assessing the information as crucial input for developing the Agency’s asteroid-hunting effort.
At 03:20 GMT on 15 February, a natural object entered the atmosphere and disintegrated in the skies over Chelyabinsk, Russia.
Extensive video records indicate a northeast to southwest path at a shallow angle of 20° above the horizontal. The entry speed is estimated at around 18 km/s - more than 64 000 km/h.
According to calculations by Peter Brown at the University of Western Ontario, Canada, drawing on extremely low-frequency sound waves detected by a global network, the object is estimated to have been about 17 m across with a mass of 7000-10 000 tonnes when it hit atmosphere.
It exploded with a force of nearly 500 kilotons of TNT - some 30 times the energy released by the Hiroshima atomic bomb - around 15-20 km above the ground.
With our current understanding of near-Earth objects, events of this magnitude are expected once every several of tens to 100 years.
Unlike Earth, the moon has no global magnetic field, but patches of the satellite’s surface are magnetic. What gives?
According to new models, these unusually magnetic pockets come from an asteroid that slammed into the moon when it had a magnetic field, billions of years ago, according to Mark Wieczorek, director of research at the Institute of Earth Physics of Paris.
In general, heating metal in a rock and then cooling it imparts magnetic properties—the most common way Earth rocks get magnetized.
“Many of the meteorites we see on the Earth contain large abundances of metallic iron. They’re roughly a hundred times more magnetic than typical rocks you can see on the moon,” said Wieczorek, who co-authored a new study on the phenomenon.
On the moon, “if we can get enough of these asteroid materials”—heated by impact—“in a certain region, that would create a magnetic anomaly that would be a hundred times stronger” than the rest of the moon.
Moon Models Show Asteroid Impact
Wieczorek and his team also found that most of the magnetic material is on the northern rim of the South Pole-Aitken basin, the biggest crater on the moon and among the biggest in the solar system.
In the new models “you start out with a 200-kilometer [124-mile] sphere and smash it into the moon—on a computer, of course—at high velocities. Depending on the impact velocity and angle, we can get large quantities of material deposited on the rim of this impact basin.”
An asteroid that size moving at 9.3 miles (15 kilometers) a second and hitting the moon at a 45-degree angle would spew out moon chunks along a 745-mile-wide (1,200-kilometer-wide) crater, the results showed.
These bits of magnetized asteroid would’ve then been deposited downward, along the rim of the crater.