The American space agency’s Osiris-Rex probe has drawn up alongside the Asteroid Bennu after a two-year, two-billion-km journey from Earth.
The mission will spend 2.5 years at the 500m-wide rock, mapping its surface and studying its composition.
In mid-2020, scientists will direct Osiris-Rex to drop down to the object and grab at least 60g of regolith, or “top soil”.
This will be packed away in a sterile capsule to be returned home in 2023.
Controllers commanded the robotic probe on Monday to fire its thrusters for 20 seconds.
This enabled Osiris-Rex to match Bennu’s velocity through space, and bring it to about 7km from the rock at closest approach.
In the coming days, the spacecraft will get a little closer to begin its preliminary survey. In the New Year, the hope is to lower the altitude of the probe so that it’s captured by Bennu’s gravity.
Asteroids are left-overs from the original building blocks of the Solar System. As such they should still retain clues to the events that brought the Sun and the planets into being.
Engineers have developed a collection device for Osiris-Rex that will extend on a robotic arm and “high five” the surface of Bennu.
On contact, this mechanism will deliver a burst of gas to kick up loose fragments that should then settle in a holding chamber prior to being packed away in the return capsule.