Are there any space rocks that could hit the Earth?

Will an asteroid really hit the Earth on Valentine's Day in 2046? Probably not!

There's been a lot of press coverage recently about the likelihood of an asteroid impact, like this article from CNN.

The short is answer is probably not - but let's look at how we classify dangerous space rocks.

What's the Torino Scale? 

Following on from some of the articles we're run recently about meteorites, we've been asked some questions about are there any space rocks currently on a collision course with Earth. Until a couple of months ago, there were none. Then a pesky one popped up and we thought it would be a good time to cover how we track asteroids and comets that pose a danger to us.

First up - there's nothing immediate to worry about!

The Torino scale is a way to measure the threat level that a particular space object poses to the Earth and the various human and non-human critters that live here. It was adopted in 1999.

It's rated from 0 to 10. All comets and all asteroids bar one that are whizzing around the Solar System are rated as a 0. This means that there's no chance of them impacting the Earth in a way that would cause damage of any concern. An objected rated as a 10 is a large object that will definitely hit Earth and cause immense damage on a planet wide scale.  This is the sort of impact that caused the extinction of the non-flying dinosaurs.

Just how dangerous an object is between 0 and 10 depends on two main factors. One is the chance of hitting the Earth. This is calculated by observing the object over a period of time and then refining its predicted orbit.  Objects initially found on path to hit the Earth that was calculated shortly after their discovery might end up missing us once further observations are made.

The other factor that makes up an object's Torino score is the likely energy released by the potential impact. This is stated in Megatons (millions of tonnes of TNT) - the same unit used to describe the power of humanity's most powerful weapon, the Hydrogen or H-Bomb.  Recent impacts such as the Asteroid 2023 CX1 that we wrote about here and which hit on the 13th of February 2023 had an energy of some 300-400 kilotons (.3 to 4. of a Megaton).  The meteor that exploded over Tunguska in Russia in 1908 released about 20-30 Megatons. The event that wiped out the non-flying dinosaurs approx. 65 million years released some 100 million Megatons of energy.

2023 DW - Torino Score of 1

As I'm writing this - 12th March 2023 - there is one object that has a "1" rating on the Torino scale. This means there's a small chance it will hit the Earth and if it does - and there's only a tiny chance it will - the impact event will be significant.  Objects are placed as a level 1 on the Torino Scale a few times a year and always bumped back down to 0 once we learn more about them.

Asteroid 2032 DW - if it were to hit the Earth - would impact us on the 14th of February 2046.

(NASA supplied illustration of an asteroid.)

Based on current orbital data, the chance of 2023 DW hitting Earth on Valentine's Day 2046 is around 600 to 1. This is small chance of happening, but if were to occur, the asteroid would impact us with a similar amount of energy that was released by the Tunguska event in 1908. This asteroid (or possibly small comet fragment) hit a remote area of Siberia where it flattened over 2,000 square kilometres of forest. If it had struck the Earth a few hours later, it might have destroyed Paris or London.

Why aren't we more concerned about 2023 DW?

First of all, the chance of impact is remote. But more importantly, astro objects that end up at 1 or more on the Torino scale are more likely to be moved back to 0 once more data and observations have been gathered about their movement through the Solar System. This happens several times a year when we discover space rocks that might be headed our way, only to reclassify them as a totally safe, "0" once more data about their predicted orbits are worked out.

2023 DW is very likely to be back to a "0" on the Torino scale by the time you read this.

Have we ever spotted anything that posed a really serious threat?

There's a been a few, but one stands out in particular.  The asteroid 99942 Apophis spent several days as a "4" on the Torino scale in December 2004. Calculations at the time gave Apophis a nearly 3% chance of hitting the Earth in 2029. As this asteroid is some 370m in size, the damage such an impact could cause would be massive and widespread. Observations of Apophis in the following weeks ruled out an impact in 2029 and based on subsequent data, it's now calculated not be a danger to the Earth for at least another 100 years.

The approx. size of asteroid 99942 Apophis compared to the Empire State Building and the Eiffel Tower

While 99942 Apophis won't hit the Earth in 2029, it will come close enough to be a seen with just your eyes at around magnitude 3.1. We'll no doubt be mentioning more about in future BINTEL posts closer to the approach.  :)

Cheers,

Earl White

BINTEL

13th March 2023