Asteroid near-miss the first of many
An asteroid which is about the size of a medium-sized home hurtled past Earth between the planet and its GPS satellites early this morning.
Astronomers say they've identified a number of these fast-moving space rocks that will pass close to Earth starting in 2017 in a flurry that will last six years.
The latest rock, named 2012 TC4, passed safely, just south of Australia, and posed no immediate threat.
But the rock does offer a rare glimpse into possible future threats to the planet which has seen a number of large strikes over hundreds of millions of years.
2012 TC4 is around 30m in diameter and travelling through space at almost 26,000km/h and passed 43,000km above Antarctica and Australia at 8.40am Central African time.
That's about the same distance as Earth's radius.
The Center for Near Earth Object Studies (CNEOS) at Nasa’s Jet Propulsion Laboratory watched the asteroid closely after it was discovered in 2012.
In that year it caught astronomers by surprise and it was known that the rock would return this year, although its trajectory was not accurately forecast until recently.
CNEOS continues to work with both professional and amateur astronomers in what is known as the International Asteroid Warning Network to decide how to cope with a real threat from an asteroid on a collision course.
There are at least 16,000 asteroids which are in close proximity to Earth but so far scientists have not found any that are likely to strike soon.
But the problem is they are extremely small in the vastness of space. If a piece of space rock the size of a house hit Earth it would have a similar amount of energy to the bomb that fell on Hiroshima.
It would destroy buildings for around 2km around the area of the strike and severely damage a city. A rock around the size of a large block of flats would destroy all buildings within an area with a 10km radius and its effect would kill everyone in a city the size of New York or London.
An asteroid about the size of a small hill would flatten everything for around 400km and most living things on the planet would die in the follow-up firestorm and dust cloud that would hang over Earth for decades.
The tidal wave associated with such a vast strike will be almost a kilometre high.
The last recorded major asteroid incident was in 1908 in Tunguska in Russia where an area of 3,100 square kilometres of forest was razed to the ground and houses 60km away were damaged in the blast.
There is a possibility of a direct strike in 2020 as observers say there are more asteroids passing through Earth's zone between 2017 and 2023 than at any time in the last few hundred years.
Asteroid 2012 DA14 in particular is being watched as it has a less than 1% chance of colliding with Earth but that's a higher probability than any recent asteroid and scientists can't rule out a possible strike.
Nasa's Jet Propulsion Laboratory said: "The orbit for 2012 DA14 is currently very Earth-like, which means it will be very close to Earth on a regular basis."
In 2014, 2014 EC flew past Earth unseen until it was on its way back out into the solar system, shocking scientists as, had it struck, it would have killed all life.
The large rock missed earth by hundreds of thousands of kilometres which is regarded as a close call by scientists.
Nasa's Ames Research Center says there are at least 2,000 asteroids larger than 1km in breadth in space and any one of these striking Earth would cause mass extinction.