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Hayabusa 2 is preparing to sample an asteroid and bring it home. Image: Wikimedia commons/Go Miyazaki CC BY-SA 4.0

Sometimes space missions can seem a bit faddish. Four spacecraft are currently orbiting Mars, and at least three missions are looking for new planets outside our solar system. But the new hotness, it seems, is asteroids.

Right now, the Japanese-led Hayabusa 2 mission is planning its next move as it orbits a space rock known as Ryugu. Inside the spacecraft, four different rover missions are ready to launch towards the surface and explore the rock. And in only a few months, Hayabusa 2 itself will land on the Ryugu’s surface, collect rock samples and then head back to Earth.

Meanwhile, the NASA mission OSIRIS-REx has just sent back the first images of its target. It is heading to an asteroid known as Bennu, and should arrive in December. Like Hayabusa 2, OSIRIS-REx is also a land-and-return mission, and aims to bring an asteroid sample back to Earth for testing.

Although Ryugu and Bennu are both near-Earth asteroids, more distant space rocks are also exploration targets.

The Dawn mission is now in orbit around the dwarf planet Ceres – the largest object in the Asteroid Belt, which is located between the orbits of Mars and Jupiter. Dawn recently turned off its engines for what is likely to be the last time, and its mission is winding down.

Even further out, the New Horizons mission is screaming through space at around 14 kilometres per second, en route to an asteroid called Ultima Thule. This asteroid is part of the Kuiper Belt, a collection of space rocks found past the orbit of Neptune. New Horizons’ visit will be very short – it doesn’t have enough fuel to stop – but it will collect a whole lot of useful data.

It might seem strange that we’re so interested in asteroids, but there’s plenty to learn from these small space rocks.

Most asteroids date back to the beginning of the solar system, before any of the planets had formed. Learning about asteroids can therefore tell us where we came from – and they may also be the key to our future. It’s very expensive to launch things into space from Earth. If we build them in space out of asteroids instead, that’s one more step we’ve gained on our journey to the stars.

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