More Planets: Tiny but dangerous ones.

“So Albert, what's next on this tour of the solar system?”

Well, we're just passing through the asteroid fields between Jupiter and the next planet we'll come to which is Mars.

“So where are all the asteroids? On Star Wars when they went into an asteroid field they were dipping and diving to miss them.”

One day I'll have to see this Star Wars film you keep talking about, but I'm not sure it gives you a very accurate picture of the universe. There are certainly plenty of asteroids it's just that space is very big.

“So how many asteroids are out here?”

I just looked up the number, by last month they had found 378,546 asteroids but they are finding thousands more every month so there may be a million or more out there. The biggest Ceres is much smaller than the earth's moon, around 600 miles across, and that single one contains a third of all the rock and ice in the asteroid belt. Here's a picture showing the Earth's moon and Ceres together.

“Is Ceres another Greek or Roman God?”

Well guessed, Ceres is the Roman God of agriculture. Ceres was the first asteroid they found and initially astronomers thought it was a new planet, until they started finding more and more of them in the same area. For a while they kept giving them names of minor Gods and Goddesses, like Pallas, Juno and Vesta.

“Then what happened?”

They were finding so many that they were running out of names, so the the discoverers starting naming them after their country, family members and even pets.
Now there are so many that most have only numbers or a scientific code. Have a look at THIS PAGE to see if anyone you know has an asteroid named after them .

“OK Albert, back in a minute...”

“Back again. I don't believe it. There are asteroids called Smiley, Doctor Watson and Asterix! Isaac Newton has his own one, but I'm afraid there's no Albert Einstein, just one called Albert.”

I think you missed one. I checked earlier and there is also an asteroid called just Einstein so that means I have two, one more than Newton.

“Oops, sorry, but guess what asteroid number 9007 is called?”

I'm not sure I know that one, sorry.

“James Bond!”

Why?

“James Bond? Double 'O' 7, get it?”

Is this a Star Wars thing again?

“No he's a secret agent, but he is in films too. Once this trip is over Albert I need to sit you down and show you all the great films you missed since you died. Oh, was that an asteroid we just went past?”

That was a fairly typical small lumpy looking asteroid yes.

“Hmm, not very exciting are they? How about getting onto the next proper planet?”

Not so fast young man, patience. They may be small but asteroids can have much more effect on the Earth than any of the monster planets we were talking about earlier.

“Such as?”

Such as killing half the living creatures on Earth for a start.

“Now you're the one talking about the nonsense from films.”

No, it really happened. That's how the dinosaurs died off and it wasn't just them. In the seas even more species were lost than on land.

“This sounds like science fiction.”

No just science but like a lot of science it started with a crazy idea that people found hard to believe. Luis Alvarez and his son Walter Alvarez made the suggestion in 1980 that an asteroid about 6 miles across crashed into the Earth 65 million years ago and caused the dinosaurs to die out.

“How could they possibly prove that?”

All over the world in rocks that were 65 million years old they found a thin layer of clay that had lots of an element called Iridium.

“What does that prove?”

Well there is very little Iridium in most rocks but there is a lot of Iridium in asteroids and meteorites.

“OK, but where's the big hole?”

They found a crater in Mexico that is now buried under the sea that dates from just the right time. They've even found a few other possible craters from around the same time in India and in the North Sea near England, so something big could have broken up and landed in several pieces.

“Oh, so people think it really happened. It's not just a crazy idea?”

No, now it's a considered the most likely reason for how the dinosaurs died out.

“Could it happen again?”

Yes it could. There was an even bigger extinction 251 million years ago when 90% of sea and 70% of land species died out. That might have been an asteroid too. The Earth is always being hit by small things, a hundred tons arrives from space every day but most are tiny particles or dust that burn up as they arrive. But there are bigger asteroids that come near the Earth and could possibly hit it one day.

“Any time soon?”

There seems to be no immediate risk, but I read that a few years ago it was predicted an asteroid called 1997 XF11 might hit Earth October 26 2028. Don't panic, they made a slight error in their calculations so it will miss by a safe margin.

“Phew. So the Earth is safe for now.”

Well...an asteroid called Apophis, the Egyptian god of evil and destruction who lives in the darkness might just cause a problem. On April 13, 2036 this asteroid has 0.0022% chance of hitting the Earth or a 1 in 45,000 chance, but on the bright side there is a 99.9978% chance the asteroid it will just miss us.

“Apophis destroying the Earth. That's straight out of Stargate, now I know you are joking.”

No, straight out of Nasa. Take a look for yourself. http://neo.jpl.nasa.gov/risk/a99942.html

“So we may have to work out how to blow up asteroids after all to save the world.”

We might.

“Is that 13th of April in 20..whatever a Friday by any chance?”

No I think it's a Sunday.

“Phew.”

Now it's time to get some practice blowing up a few asteroids. Have a go at this great Asteroids game I found.