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After a seven-year journey, Nasa's Osiris-Rex capsule has safely landed back on Earth with some very special space dust.

The spacecraft was launched back in October 2016 and its mission was to collect samples from the surface of a mountain-sized asteroid called Bennu.

It landed in the West Desert of Utah in the US on Sunday, and the sample will now be taken to a lab to be studied.

Scientists hope the studies will help them to understand how the Solar System was formed 4.6 billion years ago and possibly even how life on Earth started.

A heatshield and parachutes helped to bring the container - which is around the size of a car tyre - to a gentle landing in the desert after pelting through the atmosphere at more than 27,000mph.

"This little capsule understood the assignment," said Tim Priser, the chief engineer at aerospace manufacturer Lockheed Martin. "It touched down like a feather."

The precious cargo was whisked away to a dedicated "clean room" as quickly as possible because scientists don't want the Earth's atmosphere to interfere with the 250g of space dust they've collected.

That's because researchers think the sample contains carbon compounds that may have been involved in the creation of life so they need it to be as clean as possible to get accurate results while they test it.

The 250g sample - which is about the same weight as a hamster - will give the scientists plenty to work with.

They also want to lock some of the sample away for future generations of scientists to study.

Nasa's director of planetary science, Lori Glaze said:

"One of the most important parts of a sample-return mission is we take 75% of that sample and we're going to lock it away for future generations, for people who haven't even been born yet to work in laboratories that don't exist today, using instrumentation we haven't even thought of yet."

Nasa is planning to tell the world about its initial findings in October and distribute bits of the dust to other teams around the world.

Asteroid Bennu is a very big clump of rock - with an average diameter of just over 490 metres. It's pretty heavy as well, weighing around 78 billion kilos.

Nasa says the asteroid probably broke off a much bigger one as far as 2 billion years ago. Originally forming in the asteroid belt between Mars and Jupiter.

Because Bennu looks so similar to asteroids found on Earth scientists think it could contain some of the universe's oldest materials. This is why Nasa is so keen to investigate it - it could teach us more about where we come from.