They don't know how old it is, or how it got here, but scientists are delighted to get their hands on a lump of rock with a very special pedigree.

Channel 4 News Presenter Cathy Newman with the meteorite.

Two sonic booms and a fireball arcing through the night sky - as entrances go this one takes some beating. This was how one of the world's rarest meteorites arrived on earth - a lump of Martian rock which is now the prized possession of the Natural History Museum (NHM) in London.

(Pictured: Channel 4 News Presenter Cathy Newman with the meteorite.)

Called the Tissint Meteorite after the village in Morocco near where it was found last year, this particular invader from Mars is about the size of a paperback book and weighs just over a kilogramme. As meteorites go it is pretty big. It's also extremely rare. Of the 41,000 odd meteorites that have been found just 61 have come from Mars. It is also one of just five that have actually been witnessed falling to Earth - the last in Nigeria in 1962.

Dr Caroline Smith, meteorite curator at NHM, said: "Arguably this is the most important meteorite to have fallen in 100 years and we now have the largest piece in our collection. Martian meteorites are incredibly rare, and when they have been seen to fall and recovered quickly, like Tissint, they offer a unique insight into the red planet."

And it is how quickly the Tissint meteorite was recovered which makes it so valuable to scientists. The longer a meteorite is left before being found, the more likely it is to be contamined by earthly bacteria.

This was one was fresh off the boat, as Dr Caroline Smith explains: "Tissint fell in a dry area, was picked up soon after it fell and has absolutely minimal contamination. It is as if it has just been blasted off Mars."

• Meteorites are natural objects made of rock or iron that survive their fall to earth from space.
• About 1,000 land each year, ranging from the size of a football to the size of a washing machine.
• More have been recovered from Antarctica than any other place on Earth.
• Only 0.15 per cent of meteorites known to science come from Mars.
• The largest meteorite preserved in one piece is the Hoba iron metorite. Weighing 60 tonnes it remains where it fell near Grootfontein in Namibia.
• There has never been a recorded human death attributed to a falling meteorite.

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So what do we know about Tissint and what can it tell us about the Red Planet? Well what we can't say with any certainty is how old it is. Scientists estimate Tissint is anywhere between 175 million and 900 million years old and was probably itself blasted off the surface of Mars itself by another asteroid.

But it is what is inside the rock which is getting researchers excited. Among the layers of mineral are tiny veins of black glass. Inside those are miniscule bubbles of gas. It's these which could give scientists a snapshot of the atmosphere on Mars all those years ago, and vital clues perhaps to whether it was ever habitable.

So not exactly evidence of a little green man or even microbial life forms. But Tissint is the latest and one of the most valuable pieces making up our Martian jigsaw. A piece of rock which offers more insights into the planet's past life and perhaps could offer clues as to whether it could sustain a human colony in the future.