As OSIRIS-REx becomes the latest spacecraft to bring back samples from another world, Ezzy Pearson examines how these missions help reveal our Solar System’s history
On 24 September, NASA’s OSIRIS-REx mission will finally arrive home, the culmination of its seven-year-long journey to asteroid Bennu and back. The Origins Spectral Interpretation Resource Identification and Security – Regolith Explorer, to give OSIRIS-REx its full title, will be carrying with it an estimated 250g of dust and pebbles which it carefully gathered from the asteroid’s surface back in October 2020.
This precious cargo is being eagerly anticipated by planetary geologists around the globe, as it will be one of just a handful of pristine samples taken directly from another Solar System body. That may not be the case for long, though. Recent years have seen the number of such sample-return missions increase, heralding a new age for this particular field of space science.
These missions provide a hugely important piece in the puzzle of understanding our Solar System’s history. Four and a half billion years after its creation, our Solar System is still littered with the remnants of planets that never came to be, in the form of comets and asteroids like Bennu. Astronomers have spent centuries staring at these distant objects, while more recently orbiters and lander missions have offered a closer look. To really understand these space rocks, however, requires the use of advanced equipment that can only be found in labs here on Earth.
Snippets of the Solar System
We have long been able, of course, to look at pieces of some asteroids that have obligingly fallen to Earth as meteorites. For decades, these have been collected, catalogued and studied to give us our current picture of the disparate worlds of our Solar System. The problem is that as soon as a meteorite enters Earth’s atmosphere it’s contaminated by our environment, which limits its usefulness as a source of information. Additionally, unless the meteor was seen streaking through the sky, there’s usually no indication as to exactly where in space these rocks have spent the last four billion years before hitting Earth.
“My background is in geology, and one of the things our lecturers always say is it’s so important to do fieldwork,” says Sara Russell, head of planetary materials at the Natural History Museum. “You don’t just analyse a rock; you have to know wh
