scientists have spelled out exactly how an asteroid could kill the people unlucky enough to be caught underneath one if — or when — when it smashes into Earth.

AN ASTEROID is said to have wiped out the dinosaurs but a massive space rock could trigger the extinction of humanity too.

Now scientists have spelled out exactly how an asteroid could kill the people unlucky enough to be caught underneath one if — or when — it smashes into Earth.

Aussie hero Steven Howarth is trying to save us all from asteroidal impact — which is a good thing because they have a surprisingly large number of ways to kill us.

Researchers from the University of Southampton in the UK have set out seven different risks posed by an asteroid collision.

They published a rather ominous paper discussing “asteroid impact effects and their immediate hazards for human populations” on the same day an asteroid the size of the Rock of Gibraltar zoomed uncomfortably close to Earth.

The team used computer simulations to assess the risk posed by 50,000 different sizes of asteroid.

Their study found that asteroids caused much more death and destruction if they smashed into the ground or exploded in the sky above a land mass in an “airburst”, rather than crashing into the sea and causing a tsunami.

“The analysis of average casualty numbers per impactor [asteroid] shows that there is a significant difference in expected loss for airburst and surface impacts and that the average impact over land is an order of magnitude more dangerous than one over water,” the team wrote.

As you’d expect, the researchers also found that larger asteroids pose more of a risk than smaller ones.

However, space rocks which were smaller than about 40 metres in diameter were more likely to explode in an airburst, posing a different kind of risk to the people below.

They set out seven different ways in which space rocks could cause “loss of life”, which we’ve listed below.

Picture: NASA/JPL-CaltechSource:Supplied

WIND BLAST

The wind generated when an asteroid smashes into Earth or blows up in an airburst is the “most critical impact effect”.

Any gusts caused by an asteroid impact are likely to be so severe that they “dislocate bodies and objects to cause harm”.

The wind caused by a large space rock would tear humans limb by limb and knock buildings down on top of them.

An asteroid needs to be just 18 metres wide to cause casualties in this manner, the researchers found.

OVERPRESSURE

This is the scientific term for the shockwave caused when an asteroid explodes in the air or crashes into the ground or sea.

It was this effect which caused injuries when a meteor exploded in the sky over the Russian town of Chelyabinsk.

The researchers wrote: “Most of the damage and injuries during that event were caused by the aerodynamic shock that knocked people to the ground and damaged structures and windows, causing indirect injuries by flying glass shards.”

Overpressure can also “rupture internal organs”.

If the asteroid is large enough, the overpressure would effectively pulp victims’ insides.

THERMAL RADIATION

If an asteroid hits our planet, it will cause a massive fireball.

The effects of this are likely to be devastating to anyone caught out in the open when impact occurs.

If the asteroids hits a city or explodes above it, buildings are likely to be set on fire — with larger asteroids causing fireballs which are miles wide.

While humans would be able to shelter from the fireballs caused by smaller space rocks by sheltering in basements, the risks posed by a larger object are so great that cities would have to be evacuated if there was a risk of asteroid impact.

Thought to be the result of an asteroid impact in the heart of Australia, just west of Alice Springs, the edges of this crater have been eroded over time. Picture: SuppliedSource:Supplied

CRATERING

When an object hits a planet, it usually causes a massive crater.

Sometimes the force is so great that the asteroid instantaneously melts away.

However, the risk is likely to be quite small unless you’re unlucky enough to be in the exact area where the crater has formed.

But by the time cratering occurred, you’d probably have been blown to smithereens by the overpressure or incinerated in a fireball.

EJECTA

The process of cratering is likely to throw up a huge amount of rocks and debris into the air.

Some of these fragments are likely to be red hot, meaning they could start further fires even after a fireball had died down.

Others will be very heavy, meaning they would squash anyone in their way.

However, both ejecta and cratering are considered to be low risk because humans would have already been killed by the other effects of an asteroid impact.

If the object is large enough, however, it would send material flying into the air which could block out the sun.

If this material lingered in the atmosphere for long enough it would cause plants to die and would slowly starve everything on Earth.

TSUNAMI

If an asteroid plunged into the ocean, it would inevitably trigger a massive wave.

This has the potential to kill people who are far away enough from the asteroid to be safe from the fireball and overpressure.

But a tsunami wave takes quite a long time to spread across a large ocean, giving people the chance to save themselves by scrambling to higher land.

“Tsunamis can only reach near-coastal populations because their inland reach is limited to a few kilometres,” the researchers added.

They found that tsunamis are less of a risk than previously thought.

New Yorkers run for their lives as a tsunami floods the streets of New York City in ‘The Day After Tomorrow’.Source:AP

SEISMIC SHAKING

An asteroid impact would likely cause an earthquake.

But quakes are only considered to only have a “minor effect” on the number of casualties.

The asteroid is unlikely to cause the same sort of devastation caused by the sort of natural disasters humans are familiar with.

If you’re far away enough from the asteroid that you don’t have to worry about being burned alive or blown to bits, you probably don’t have to worry about earthquakes shaking your house down on top of you.

This article originally appeared in The Sun.