Despite the fact that the Earth is naturally constantly bombarded with extra-terrestrial matter (as much as one hundred kilograms of space dust and meteorites is estimated to fall on the Earth each day), the amount of “space rocks” brought back to Earth by human endeavour is incredibly small. Less than 400 kg of rocks, for example, were retrieved from the Moon by the Apollo program (about 80kg of which are currently “missing”). The only known Martian material on Earth was retrieved as meteorite debris. A Japanese probe, Hayabusa, was the first to return samples from an asteroid, in 2010.
A current space mission is about to make a tiny, but scientifically invaluable, addition to Earth’s collection of “astromaterials”.
A week after collecting a sample from the near-Earth asteroid Bennu, NASA’s OSIRIS-REx spacecraft will stow the sample to protect it from leaking into space on Tuesday.
The probe was, in fact, a victim of its own success.
The mission team received images sent by the spacecraft last Thursday that revealed the sample collection head was full of surface material — so much so that a flap was wedged open by rocks, allowing particles to escape into space.
The team canceled scheduled maneuvers for the spacecraft that would have been used to estimate the mass of the sample they collected. But the researchers are confident that the spacecraft collected well over the mission’s requirement of 2 ounces or 60 grams.
Due to the success of the sample collection, the team worked over the weekend to expedite preparations for stowing the sample, which was originally scheduled for November 2.
Stowing the sample securely is absolutely necessary to protect the samples from the rigours of atmospheric re-entry, not to mention contamination on Earth.
The fact that the probe managed to collect too much material is even more astonishing when considering the brevity of its touch-and-go contact with the asteroid. The OSIRIS-REx probe landed on the surface of Bennu for roughly six seconds. Now it has to make the 200-million mile journey back to earth.
Stowing the material is a delicate process made even more painstaking by the near-20 minute delay in communication between the probe and Earth.
Each stage of stowing the sample requires oversight and commands sent by the team. Basically, every time the spacecraft completes a step, it sends back data and images to the team. Once the researchers receive them, they assess OSIRIS-REx’s progress and sends another command.
This will ensure that the collection head is placed in the capsule with proper care.
This stowing process will take multiple days by the team’s estimate, but this should result in the sample being safely stowed and sealed so it can return to Earth.
The spacecraft won’t actually begin its journey home until March 2021, when the planets are in favourable alignment – that is, when the distance between Earth and Bennu is such as to minimise the amount of fuel needed to drive the spacecraft home.
The material collected is expected to further our understanding of the early solar system. Asteroids like Bennu are considered “primitive” because they have undergone little geological alteration since their creation. So the samples will be a geological snapshot of the beginnings of the solar system. More importantly, Bennu is an unusual “B-type” asteroid which likely includes high amounts of volatile chemicals and perhaps water ice. As such, it may indicate how favourable conditions in the early solar system, on the whole, were to life.
At a long reach, it may even lend credence to the “panspermia” hypothesis that life is “seeded” through the universe by space dust, asteroids and comets.
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