Sen— On 15 February, Earth had its biggest run-in with a cosmic missile for a century when a brilliant meteor exploded over the Siberian city of Chelyabinsk.
The brilliant fireball, dubbed a superbolide, appeared literally out of the blue shortly after sunrise and was captured by many cameras, including the dashcams that are often fitted to Russian cars.
But from space a NASA satellite was watching too and has provided incredible data showing that dust from the meteor quickly spread right the way around the world.
The meteor, about 18-metres across and weighing 11,000 metric tons, exploded over Chelyabinsk with more than 30 times the energy of the atom bomb that devastated Hiroshima.
It produced an airblast that shattered windows, damaged buildings and injured more than 1,000 people before showering meteorites around - and in - Lake Chebarkul. The blast was detected by listening stations as far away as Antarctica.
But as well as breaking into meteorites, the explosion also deposited hundreds of tons of dust high in the stratosphere. This allowed a NASA satellite to observe as never before how the material formed a thin but cohesive and persistent stratospheric dust belt.
The Ozone Mapping Profiling Suite instrument’s Limb Profiler on the NASA-NOAA Suomi National Polar-orbiting Partnership satellite detected the plume high in the atmosphere about 3.5 hours after the initial explosion. It was at an altitude of about 40km (25 miles) and moving swiftly east at more than 300kph (190 mph).A video shows how the satellite followed the dust from the Chelyabinsk superbolide around the globe. Credit: NASA
A study of the dust was led by atmospheric physicist Nick Gorkavyi, of NASA’s Goddard Space Flight Center in Maryland, who by chance happens to come from Chelyabinsk. He said: “We wanted to know if our satellite could detect the meteor dust.
“Indeed, we saw the formation of a new dust belt in Earth’s stratosphere, and achieved the first space-based observation of the long-term evolution of a bolide plume.”
Gorkavyi and his colleagues combined a series of satellite measurements with atmospheric models to simulate how the plume from the bolide explosion evolved as it was carried around the Northern Hemisphere by the stratospheric jet stream.
A day after the explosion, the satellite detected the plume continuing its eastward flow in the jet and reaching the Aleutian Islands. Larger, heavier particles began to lose altitude and speed, while their smaller, lighter counterparts stayed aloft and kept their speed.
By 19 February, four days after the blast, the faster, higher portion of the plume had snaked its way completely around the Northern Hemisphere and back to Chelyabinsk. But the plume continued to evolve and at least three months later, a belt of bolide dust was still detectable around the Earth.
Dust from space is plentiful at the highest altitudes. Every day, about 30 metric tons of small material from space encounters Earth and is suspended high in the atmosphere. It is thought to be a contributor to the appearance of Noctilucent Clouds which can be seen shining at night in mid-summer from northern latitudes.
Meanwhile, scientists in Spain have looked at the orbit deduced for the Chelyabinsk meteor and say that it could have many relatives that might impact the Earth in the future. Brothers Carlos and Raúl de la Fuente Marcos, both professors studying orbital dynamics at the Complutense University of Madrid, ran billions of computer simulations to help them identify around 20 asteroids on similar tracks.
The best match, they say, is a 200-metre wide asteroid labelled 2011 EO40. The brothers believe that both could be fragments of a larger asteroid that broke up between 20,000 and 40,000 years ago.
They say that a sample return mission by a space probe, or the cheaper alternative of analysing 2011 EO40’s light with a spectroscope to see what it is made of, could help confirm a link.
Carlos told Sen: “Honestly, I doubt the unmanned mission is a feasible option taking into account the current economic context. But a large ground-based telescope, or the Hubble Space Telescope, may be able to obtain the spectrum of the asteroid in June next year.”
He added: “We may have had impacts from this group of objects in the past and we may have additional impacts in the future. Having better orbits for all these objects can help to clarify the answer.
“If additional fragments are on a collision course, it is very likely that they will be smaller than the one responsible for the Chelyabinsk event and therefore, not particularly dangerous.”