Experts on meteor strike in Russia

UK SMC: Residents of the Russian city of Chelyabinsk are recovering after a meteor broke up over the city causing hundreds of injuries and damaging buildings.

Our colleagues at the UK SMC gathered the following commentary from scientists:

Dr Simon Goodwin, Reader in Astrophysics from the University of Sheffield’s Department of Physics and Astronomy, said:

“Objects from space are hitting us all the time.  Estimates are that 1,000 – 10,000 tonnes of material from space rain down onto the Earth every day. The vast majority are small (mm or cm) and burn-up high in the atmosphere. These ‘shooting stars’ look pretty and cause no damage at all.

“How far something gets through the atmosphere depends on how big it is and what it’s made of.  Metal or solid rock meteors can often get to the ground and meteor hunters go looking for these in deserts and on ice (somewhere where the colour of the meteor is different to that of the ground).

“If a meteor makes it all the way to the ground it can produce an impact crater and possibly do significant amounts of damage.  A meteor crater in Arizona is over a km across caused by an impact about 50,000 years ago. The impact that killed off the dinosaurs 65 million years ago has a crater 200km across hidden under rock in Mexico.  There are quite a few impact craters on the earth, but most are hidden under sediment and are difficult to spot.

“It seems like the damage from the meteor in Russia yesterday was not due to the meteor hitting the ground.  It seems to have been caused by a shock wave as either the meteor broke the sound barrier, or maybe exploded in the air. This shock wave then broke windows and caused the damage and injury.  Probably the area is covered with tiny bits of meteor if it did airburst, and maybe there is a small impact crater but I have heard no reports of this yet.

“This could be a less extreme version of the Tunguska event in 1908 when we think a meteor exploded in the air above Siberia flattening about 2,000 square km of thankfully uninhabited forest.

“While events this big are rare, an impact that could cause damage and death could happen every century or so.  It very much depends on where it hits – the Tunguska impact killed nobody, but if it had hit a few hours later it could have killed a million by exploding over St Petersberg.

“A big enough (few hundred m) meteor could cause significant immediate death and maybe cause climate change by releasing dust into the air – these are maybe every few thousand years.  An impact into the sea could cause a world-wide Tsunami causing lots of damage in any low-lying area.  And a really big (km) impact occurs every few tens of millions of years and can cause mass extinctions (one killed the dinosaurs).

“This has happened at the same time that the asteroid 2012 DA14 is passing fairly close to Earth.  They might be related, but probably not.  Asteroids pass close to us very often (most of the time we have no idea), and impacts occur constantly and airbursts happen a few times a year (often above the ocean or uninhabited areas, we only know about these by spotting them from satellites)

“Scientifically this is not hugely interesting as we collect bits of meteor from all over the world already.  Probably its greatest importance is to make people realise that things fall from space all the time, and every now and then they can be dangerous – maybe very dangerous.

“Unfortunately there is absolutely nothing we can do to stop impacts. So far there are no confirmed reports that anyone has ever died due directly to a impact, but it will happen eventually.  And an impact in a heavily populated area could kill huge numbers of people with no warning or chance of stopping it.”

Dr Hugh Lewis, Lecturer in Aerospace Engineering, University of Southampton, said:

“Small meteors enter the Earth’s atmosphere quite frequently (shooting stars can be seen every night, really) and we might see a relatively large fireball once a year, maybe. Something like this event (a 10 ton object, according to an AP report citing the Russian Academy of Sciences) is rarer.

“The UK saw a meteor in September last year. Experts at the time thought it was space debris because of its apparent slow speed, but it was later confirmed to be a meteor.”