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The asteroid adventurer
We’ve all felt the anticipation of waiting for a parcel, eagerly listening out for the ring of the doorbell.
Now imagine a special delivery that could tell you about the origin of planets and offer a glimpse into the future. Would you be patient enough to spend years preparing for its dispatch and wait another seven years for it to come back?
That’s the exact situation that Prof Sara Russell from the Museum’s Earth Sciences Department finds herself in as part of the team working on a mission to collect samples from the asteroid Bennu.
Computer generated image of the asteroid Bennu, with OSIRIS-REx nearby © NASA Goddard Space Flight Center
This near-Earth asteroid was first discovered in 1999 and has been the subject of extensive observations using telescopes on Earth and in space ever since. Scientists now know the size, shape and colour of Bennu, and how it moves through space. It is coming closer to our planet every six years on its orbit around the Sun.
To find out if their long-distance data is correct, researchers are planning to send a spacecraft to inspect Bennu at close quarters and even collect samples from its surface to bring back to Earth. The mission is called OSIRIS-REx and, after more than a decade of planning, the launch is scheduled for 2016.
Space rocks
Although it is a US space mission, Prof Russell was invited to join the OSIRIS-REx science team thanks to her expert knowledge of meteorites, objects from outer space that end up on Earth.
‘We think most meteorites date from the earliest time in the solar system when the planets were forming and most of them come from asteroids which were the building blocks of planets,’ she explains.
While some of these meteorites were altered by water running through the asteroids and exposure to heat from impacts, the Sun, or radioactive isotopes, others remained in their original form.
‘There are a few special meteorites, in particular some carbonaceous chondrites, which basically have been untouched since the beginning of the solar system - they seem very pristine,’ says Prof Russell.
Prof Russell and the Murchison meteorite, named after the village in Australia where it fell in 1969
The Museum’s collection contains a number of these prized carbonaceous chondrites. The dark, grainy lumps of the meteorites may look unassuming, but they hold secrets to the beginning of the solar system.
Pristine condition
Prof Russell is careful when handling these samples, not because they are dangerous but because they are delicate. One of the meteorites contains extra-terrestrial organic material and is kept in a protective bag to preserve it, another is encased in a box with a nitrogen-rich atmosphere to minimise contamination.
‘That’s one of the reasons we need a space mission and we can’t rely on meteorites falling, because everything that comes into the Earth’s atmosphere becomes contaminated,’ says Prof Russell.
‘If you want to find out what something is really like in its primal state you have to go and collect it in circumstances you can control.’
So far, analysis of Bennu suggests that it is similar in composition to the Museum’s carbonaceous chondrites.
‘We think these almost black asteroids are primitive remnants from our early solar system and they’ll tell us what the environment was like 4.5 billion years ago when planets started to form,’ says Prof Russell.
By studying the meteorites under the microscope and using X-ray techniques, Prof Russell is able to advise the OSIRIS-REx team on what to expect when sampling the asteroid. Details of the potential texture and mineral make-up of the asteroid also help to establish a geological map of Bennu that will allow scientists to choose the all-important sample site.
For Prof Russell, it's a personal as well as a scientific endeavour:
‘We’re learning about things that are unimaginably far away and happened a very long time ago but to me it’s immediate. I've been handling and analysing and dreaming about these meteorites for decades.’
OSIRIS-REx mission video, courtesy of NASA/Goddard Space Flight Centre
Collision course
As well as collecting samples to tell us more about the past and prove present observations, the OSIRIS-REx mission is looking to the future. According to their calculations, scientists predict there is an outside chance that Bennu could collide with the Earth in 200 years.
‘Bennu was chosen as a target partly because it has this potential to be hazardous,’ says Prof Russell. She explains that the close-up observations of Bennu will help scientists better understand how asteroids move around the Sun, and consequently how hazardous they might be to the Earth.
Although she is busy with analysis for the mission and other meteorite research, Prof Russell is also looking ahead to 2016. She will travel to the US to watch the mission launch with her colleagues at NASA, but she will not be able to interact directly with the asteroid samples until they safely touch down on Earth in 2023.
‘This is such a long-term project, but the sample collection is only going to take five seconds. If that goes well then I’ll feel it’s all going to work out alright.’
Prof Russell’s patience is a true testament to her love of astronomical objects and the exploration of the unknown.
