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Illustration of the OSIRIS-REx sample return capsule passing through Earth\u2019s atmosphere<\/p>\n
NASA Goddard Space Flight Center\/CI Lab<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Bits of the asteroid Bennu are coming back to Earth. NASA\u2019s OSIRIS-REx spacecraft took samples of the asteroid in 2020 which are scheduled to arrive on Earth on 24 September.<\/p>\n
OSIRIS-REx launched in 2016 and entered orbit around Bennu in 2018. Scientists chose Bennu as a target primarily because of its relatively small distance from Earth \u2013 at the time of launch, it was about 225 million kilometres away, and in the intervening years it got as close as 50 million kilometres from Earth.<\/p>\n
Because of its regular close approaches, Bennu is considered a near-Earth object (NEO). It\u2019s not expected to smash into our planet anytime soon, but there is about a 0.057 per cent chance of a collision in the next 300 years. Bennu is about 490 metres across, so if it did crash into Earth it would cause significant damage.<\/p>\n
One reason to study Bennu is to figure out how to protect Earth from it and similar asteroids. But another is that it is one of the most primitive space rocks we know of. \u201cAsteroids like Bennu are time capsules from the early solar system, debris that\u2019s left over from the formation of the solar system,\u201d says Anjani Polit at the University of Arizona, part of the OSIRIS-REx team.<\/p>\n
Such asteroids probably clustered together to form our solar system\u2019s planets, so we can use them to understand how the planets formed and grew. Bennu in particular hosts large concentrations of carbon, the main building block of organic molecules \u2013 which in turn are the building blocks for life as we know it.<\/p>\n \u201cWe\u2019re pretty sure that there will be organic molecules in these samples,\u201d says OSIRIS-REx scientist Michelle Thompson at Purdue University in Indiana. \u201cStudying these organic molecules might help us understand what organics were around in the early solar system that could have seeded life on Earth.\u201d<\/p>\n Similar samples have already been returned by Japan\u2019s Hayabusa2 spacecraft, which visited an asteroid called Ryugu. A key component of the researchers\u2019 goal of understanding the history of the solar system will be comparing dust samples from these two objects.<\/p>\n \u201cLet\u2019s say you are a visitor to Earth and you want to learn all about Earth\u2019s geologic history, so you pick up one rock \u2013 you\u2019re never going to be able to learn that,\u201d says Thompson. \u201cGoing to more than one different asteroid really opens up a whole new world to really understand the diversity of material that was around 4.5 billion years ago\u201d, about the time when the solar system formed.<\/p>\n On 24 September, the day will start early for the OSIRIS-REx team. In the wee hours of the morning, the team\u2019s engineers will make a call about whether it is safe to release the sample capsule. If they give the \u201cgo\u201d, it will be sent hurtling towards Earth from about 102,000 kilometres away, more than a quarter of the distance to the moon. It will travel for about four hours before slamming into the atmosphere at around 44,000 kilometres per hour. During its descent, it will be protected and slowed by a heat shield and two parachutes until it touches down in the Utah desert.<\/p>\n \u201cOnce we release the capsule, there\u2019s nothing else we can do except wait and hope everything goes smoothly,\u201d says Polit. \u201cAll these years of work, it all comes down to that 13-minute descent through the atmosphere.\u201d If the capsule cannot be released on 24 September, it will be two years before researchers have a chance to try again.<\/p>\n If it can be released, though, the OSIRIS-REx spacecraft will continue on towards an extended mission at the asteroid Apophis. On Earth, the sample it drops will be immediately scooped up and sent to Houston for scientists to analyse. \u201cI honestly feel like a kid on Christmas Eve,\u201d says Thompson. \u201cI\u2019m about to wake up and get all these gifts of samples from Bennu.\u201d<\/p>\n Topics:<\/p>\n<\/section><\/div>\n