Flying a spacecraft, catching up with an asteroid, then flying alongside that asteroid without crashing into it is – to put it mildly – a challenging activity.

Amazingly, this week, Nasa's Osiris-Rex probe sidled up alongside a diamond-shaped asteroid known as Bennu and is doing just that.

Osiris-Rex stands for Origins, Spectral Interpretation Resource Identification, Security-Regolith Explorer. By understanding how asteroids like Bennu fly and how their trajectories are shaped, the researchers hope to improve prediction models for asteroid impact forecasts - just in case one of those large space rocks is set on a course towards Earth.


Nasa's first asteroid-sampling mission, Osiris-Rex has this week arrived at its destination. It has been chasing the 500m-wide rock for the past 27 months and has covered two billion kilometres in the process.

Now that it's caught up with the asteroid, it will fly alongside it for the next four weeks mapping its surface and studying the rock's composition. After that, the probe will scout the surface for the best place to try to collect a sample.

The goal is to collect a sample of the asteroid and transport it back to Earth for in-depth scientific analysis. Hopefully, by July 2020 the perfect location will have been found and sample collection will be able to take place.

Rather than land on the asteroid, the plan is to "tap" the asteroid with a long arm. The arm, known as the Touch-and-Go Acquisition Mechanism (Tagsam), will then vacuum at least 60g - but potentially up to 2kg - of the asteroid's regolith, the nearest equivalent to what we on Earth would refer to as topsoil.

This Tagsam vacuuming process will be incredibly fast, taking just five seconds to complete – almost like an interplanetary high five. Following the transfer, Osiris-Rex will stay close to Bennu until March 2021, before returning to Earth sometime in 2023.

Asteroids are leftovers from the original building blocks of the solar system, which means that they hold the clues to events that created the sun and the planets. The goal, through analysis of the regolith material, is to better understand the initial days of the solar system, as well as to examine the role that carbon-rich asteroids like Bennu might have played in the emergence of life on Earth and possibly other planets.

There are some fascinating complications involved in manoeuvring in close proximity to an asteroid like Bennu, which will become the smallest object ever orbited by a probe.

The asteroid's relatively small size and low mass mean that it's gravitational field is insufficiently strong for the probe to enter a traditional orbit – Nasa's scientists are having to develop new techniques to remain in close proximity to the rock for the duration of the mission.


Further complicating matters, the heat of the sun on the side of the spacecraft will cause the probe to emit thermal energy – that emission will change the probe's trajectory ever so slightly – all of which needs to be factored into the controller's calculations.

Data from this mission will be invaluable to the growing space economy of which asteroid mining is still a goal. There is a large economic incentive to try to determine the best way to try to mine raw materials from asteroids for use in space for construction and fuelling rather than having to launch these materials from earth or even for bringing back to earth if we use up all of our readily available resources.

For now, we household chore avoiders should take note – an interplanetary vacuum cleaner may be about to change the world.